Paving Terminology
Paving with a riven surface has a naturally rippled finish created along the seam of the rock where it has been split. This finish follows the natural veins within the rock. This gives an attractive, irregular and gently undulating surface texture. Riven surface paving is often seen in sandstone, limestone and slate paving, but is also manufactured artificially with concrete paving to offer the appearance of natural stone. The appearance of a riven stone works well in both traditional and modern styled gardens and the irregular surface finish is easy on the eye and natural. Although the stone has ridges on the surface, these are not significant and are usually very subtle.
A sawn surface paving means it has been cut with a flat uppermost face. Often seen as a contemporary option, sawn paving is known for having more of a sleek, clean finish and having a flatter profile makes it ideal if a riven surface is undesirable. A sawn surface is only the primary process as it will usually be accompanied by one of the textures shown below to finish the product to the required look. In many cases, products with a sawn surface will also have sawn edges, however this is not guaranteed to be the case, so always read the product description to be sure.
A honed finish paving stone is achieved by applying abrasion to the surface of the stone to bring out the natural colours. A honed surface feels smooth to the touch and has a sawn flat surface. This finish is ideally suited to contemporary garden designs schemes, especially where a natural stone with its blend of colours is desirable. A honed finish is often applied to stone such as sandstone. If a smooth finish is required, but without the colour blend of natural stone, then a porcelain paving product would be a good alternative for paving with a similar appearance. In terms of slip resistance, honed natural stone will always be less slip resistant than a riven or textured stone surface whereas a porcelain paving option would have a high slip resistance rating whilst maintaining the visual impact of a honed stone.
Sandblasted and shotblasted paving involves primarily producing natural stone with a sawn flat, honed surface which is then peppered with either shot (small beads of steel) or sand under high pressure to give a stippled appearance and good slip resistant qualities. This paving will feel lightly textured to the touch and as a general rule, sandblasted stone has a fine, less stippled surface than shotblasted paving. The flat nature of this type of stone makes it suited to contemporary styles where a more practical, slip resistant finish is required. As a general rule, the types of stone that are shotblasted or sandblasted are sandstone, limestone or granite. As an alternative, consider porcelain paving as this too has a flat surface with a slip resistant texture.
With tumbled stone, this is produced by vibrating and rolling the stone through a machine similar to a cement mixer that wears down the surface and often the edges too, to give a timeworn appearance as though the stone has aged over several centuries. It is designed to work well with period homes or where an aged or distressed finish stone is desirable. Typical stone types for tumbling are sandstone, limestone, granite paving and some ranges of concrete block paving are also tumbled (rumbled) to give a cobblestone effect. The stone may be sawn flat or have a riven surface to begin with and this creates paving stone products with either a flat suface, but with timeworn edges and a slightly smoother surface or a heavily worn and smoothed down riven texture.
Stone with a brushed surface is rubbed with hard bristle brushes to give a worn down appearance as though it has naturally weathered over time. Due to the irregular surface texture of stone with a brushed surface, it has a soft, natural appearance and is easy on the eye. It is typical to find a brushed surface in paving stone such as sawn or riven limestone, quartzite and slate. Brushed texture stone is an interesting informal finish that softens the appearance of the primary texture. As with all paving with secondary processing, paving slabs with a brushed surface will be less economically priced than a natural riven surface.
Flame texturing is a process where the surface of the paving is burnt with a hot flame to burn away the softer minerals within the stone, often enhancing the colour of the stone, especially with granite. This technique can be performed on both natural riven and sawn finish paving and creates an informal, softer appearance to the stone texture. With sawn stone such as granite, the texture becomes lightly stippled as the softer minerals are removed to leave the harder textured components of the stone, but with more on an irregular finish than seen with a sandblasted or bush-hammered texture. With a riven stone, the flaming softens the angular appearance of the ripples on the surface to create an appearance similar to a water worn surface. As a general rule, it is often sandstone, quartzite and granite that is flame textured.
Bush hammering is a process where a tool similar to a meat tenderiser is applied to the surface of the paving to give a stippled, slip resistant surface. This finish is not dissimilar in appearance to a sandblasted or shotblasted stone. Bush hammering is not widely used and tends to be utilised for paving such as yellow granite which is unable to be flamed due to its tendency to turn pink when exposed to heat from the flame thrower.
PAVING EDGE FINISHES
A handcut edge finish has been carefully and painstakingly fettled by hand to create a naturally wavy appeal. This works well where a natural, informal appearance is desirable and is quite standard in most sandstone and limestone riven surface paving options. With many types of paving the handcut edge is tapered and it is important to note that the larger face of the paving slab should always be laid uppermost. The natural wavy finish is very insignificant in appearance once the paving is laid. Due to the irregular nature of the edge, it is necessary to allow a jointing gap in the region of 15-20mm between each paving slab. Dimensions of each slab may vary slightly from the given measurements and by leaving the correct jointing gap, this will allow for any variations to be absorbed into the jointing gap.
A sawn edge finish stone has been cut straight to offer a contemporary styled design. With some types of stone such as porcelain, granite paving slabs and slate, it is usual for these to have sawn edges as standard, whereas other products such as sandstone and limestone will usually have handcut edges unless it specifically states to the contrary. Although natural stone paving with a sawn edge can often be laid closer together than that with a riven edge, there is always a tolerance in dimensions of natural stone meaning that a 15mm +/- gap will need to be allowed. It's also important to note that no natural stone product is ever precision cut and there will always be a tolerance on dimensions in addition to imperfections along the edge line where it has been cut. Porcelain paving on the other hand can usually be laid with a closer joint between slabs, however read the section below on Rectified and Non Rectified finishes which apply specifically to porcelain paving.
Paving that has a tumbled edge finish has been vibrated and rolled in a machine similar to a cement mixer to give the appearance of a stone that has aged over several centuries. The attractive rounded edges make this antique style stone ideal for older style properties or those where a classic aged stone is required. Typical stone types with a tumbled edge are sandstone, limestone and concrete; the latter is created mainly for driveways to give the perception of an aged cobblestone. Tumbled stone may have imperfections around the edges where the stone has been battered to give the aged look and this all adds to the character of the stone.
A bullnosed edge is the front finish to many step units and comprises a specially rounded edge that is not only attractive to look at, it is practical too as it reduces the risk of the front edge becoming chipped or damaged. This finish is available in many products as standard and all steps will have paving ranges to match. See details here. Further to this, it's possible to have steps made to order to match the paving with many ranges, so be sure to enquire about these.
With most natural stone, the front of the bullnose will appear very similar to the stone surface, albeit sometimes a bit smoother. With porcelain paving where the colour of the stone is shown on the surface of the stone only, the front of the bullnose which is machined along the profile of the paving will not have the same patterning as the uppermost face. With full bodied porcelain, the body colour of the porcelain is carefully manufactured to match the uppermost face as closely as possible, so although the pattern will not follow onto the bullnosed edge, the overall colour will be a good match. With colour bodied porcelain which is more economically priced than the full bodied ranges, the body of the paving is still a good match, but is not as close to the uppermost colour as the full bodied ranges. This means that the front edge shown onn step treads with a colour bodied range will be slightly more noticeable.
The other point to note when using porcelain paving for bullnosed steps is that there is often a dark vein (black heart) running horizontally through the stone. As a general rule, this is very subtle along the outer edges of paving slabs, but if a stone is cut, then it is not good practice to use the internal cut edge in an exposed position such as the front of a step tread as the dark vein will be more prominent on cut edges.
Many of our porcelain ranges can have accessories such as bullnose step treads made to order. See here for the ranges where this is possible.
With porcelain paving, the accuracy of the dimensional tolerances depend on whether the paving is 'Rectified' or 'Non Rectified'. With rectified paving, it is cut to size after firing in the kiln meaning there will a smaller tolerance between the size of individual paving slabs within the batch. This tolerance may be up to 2mm +/-.
The actual slab dimensions are nominal and can be smaller than the stated measurements by up to 5mm, however the variations between slabs will only be 2mm +/-. It is best practice to use the same batch number when laying porcelain paving as this will ensure the variation in sizes between the slabs is minimal.
With porcelain paving, the accuracy of the dimensional tolerances depend on whether the paving is 'Rectified' or 'Non Rectified'. With non rectified paving, it is cut to size prior to firing in the kiln and may expand or contract during firing.
As a result, the dimensional differences between each paving slab may be up to 5mm +/- and jointing allowances will need to be gauged accordingly. It is also important to note that slab sizes are nominal and may be up to 5mm smaller than those stated. It is best practice to use the same batch number when laying porcelain paving as this will ensure the variation in sizes between the slabs is minimal.
PAVING THICKNESS
Paving with a variable thickness means there is a variance in thickness between the stones as shown on the product details, for example, 15-25mm or 35-50mm. This may also mean there is a variation in thickness within the same individual piece of stone. There is also a tolerance on the measurements in accordance with British Standards (UKCA) that allows for a further variance on the stated measurements which is often in the region of 5mm +/-. The measurements are nominal and should be indicative of the overall thickness of the range rather than each piece of stone following precise measurements. Any minor variations in thickness will have no bearing on the finished project or the strength of the stone and will often be more prevalent on stone with a riven surface.
Visually once laid, it will not be possible to determine if paving is calibrated or variable. When examing the stone prior to laying, it is often the case that the underside of variable stone will be similar in appearance to the uppermost face, although if the stone has tapered edges, it is always the smaller face that should be laid downwards.
When laying paving with a variable thickness, the important factor is that the levelling off takes place on the surface of the stone and any differential in thickness is made up within the bedding mortar.
As a general rule, paving with a variable thickness is often better value than paving with a calibrated thickness.
Calibrated paving has been cut to a more consistent thickness and the variation between both individual and the same slabs will vary by only a small amount. In accordance with British Standards (UKCA), this is usually a maximum of 5mm +/-. All measurements are nominal and should be indicative of the general thickness of the range rather than precise measurements of individual pieces of stone. Any minor variations on thickness will have no bearing on the finished project or the strength of the stone and can often be seen especially on riven surface stone.
From a visual perspective, calibrated natural stone usually appears different on the uppermost face to underside with the underneath either appearing with a corrugated / partially corrugated finish or with stone such as granite, the underside will be smooth and matte in appearance with machine marks. With concrete and porcelain, there may be manufacturing marks or patterns on the underside.
When laying calibrated paving, this should be applied to a full mortar bed and any minor tolerances in dimensions may be taken up within the bedding layer.
Natural Stone Geology
Natural stone is a stunning material with sometimes subtle and sometimes diverse variations between each unique piece of stone. It is known for its strength, frost resistance, ease of use and timeless appeal. It is ahead of most other types of building materials for its green credentials.
Stone is formed from different geological processes which contribute to the characteristics seen within the stone and the three major groups of rocks from which paving stone is produced are as follows:
Igneous
Igneous rock is formed as either 'extrusive' or 'intrusive'. Extrusive rock is formed from lava which has cooled rapidly on the Earth's surface forming small crystals within the stone. An example of extrusive rock is basalt. Intrusive rocks on the other hand are created within the Earth's crust without an eruption and as such, the magma cools slowly allowing larger crystals to form within the rock and this is typical of stone such as granite.
Sedimentary
Sedimentary rock has formed by layers of sediment desposited in a desert or underwater and gradually compressed over millions of years. Examples of sedimentary rock include sandstone and limestone. Sandstone is formed mainly of silica sediment with shade variations and unique banding whereas limestone is mainly formed from carbonates such as calcite and dolomite.
Metamorphic
Metamorphic stone has changed from its original state of either igneous or sedimentary rock by exposure to concentrated heat or pressure. This causes them to become a denser rock. Examples of metamorphic rock includes quartzite, marble and slate.
Porcelain and vitrified products are manufactured from naturally occurring aggregates including highly refined and purified clay, finely ground sand, cement and binders. It is compressed and then fired in a kiln at 1200 Celsius removing virtually all moisture to create an extremely hardwearing and low maintenance use suited to various applications including patios and pathways, driveways and wall cladding.
Porcelain paving has excellent credentials: it is hard wearing, scratch and abrasion resistant, almost completely impervious to moisture meaning it is not impacted by salts, oils and chemicals. This low porosity also makes it resilient to algae, fading and other staining. Porcelain is highly resistant to extremes of weather such as heat and cold and its, R11 rated slip resistant, lightly textured finish makes it perfectly suitable for use on patios, around pools and on driveways.
Visually, porcelain comes in a variety of colours and styles. The pattern is printed onto the wet clay during the manufacturing process and depending upon the range, there may be a wide range of different patterns to create an informal, natural effect rather than seeing a repetitive pattern. Due to the resilient and low maintenance nature of porcelain paving, it is available in many colour shades including white and light cream which may be impractical to maintain with other types of stone.
Unlike ceramic and other glazed tiles, porcelain is quite matte in appearance. It is often made to resemble natural stone, but without the imperfections and natural characteristics seen with a natural counterpart.
Porcelain usually has a flat surface, albeit with a slight texture, and sawn straight edges. As a guide, it is 10mm thick for indoor use, 20mm thick for patio use and at least 30mm thick for driveway use. The indoor ranges usually have less of a texture than the outdoor porcelain. Some specialist ranges such as Brett Geoceramica, Marshalls Symphony Plus and Stonemarket Una combines a 10mm porcelain tile bonded to a 30 - 50mm (depending on range) concrete back which is concealed once the product is laid. The purpose of these paving slabs is to allow installation onto a sand bed instead of a full mortar bed. The thicker ranges are also suited to driveways meaning that a large contemporary slab size may be used on a driveway instead of a more traditional block paving product. Unless one of the specialist ranges above have been used, then all other porcelain ranges must be laid onto a full mortar bed. This must be used in conjunction with a priming slurry applied to the back of the slab prior to pressing onto the mortar which is required due to the low porosity of porcelain needing the extra adhesion this offers to ensure the paving sticks to the mortar.
When cutting porcelain, it is important to not allow the paving to get hot and to minimise vibration. Always use a specialist porcelain blade such as the Pavetuf porcelain blade with a wet cut and if possible, cut on a sand bed to avoid the stone vibrating. Take it slowly to avoid the stone overheating.
When ordering porcelain, it is recommended that you purchase the full amount required at the same time. This is due to porcelain being produced in batches and it is best to ensure the same batch is used throughout your project. Different batches may have different colour tones and slab sizes.
The sizes of porcelain paving are either described as Rectified or Non Rectified. Click on the links to read more. In summary, the dimensional tolerances with rectified paving are far smaller than those in non rectified paving and as such, rectified will allow for a closer joint between slabs when laying. Slab sizes can vary between batches of the same stone, so always try to work with the same batch where possible.
When porcelain is manufactured, the colour is ink-jet printed onto the surface of the wet clay body. The colour of the clay body is either described as 'full-bodied' or 'colour-bodied' and this determines how close this colour matches the surface finish should the slab become damaged or chipped. If the paving is full-bodied, the colour of the clay is carefully chosen to match as closely as possible to the surface colour and this is considered a premium product. Colour bodied paving still offers a good match, but is not created to match to the same level of accuracy as full-bodied and as a result, the prices of this product type are more economical.
Porcelain paving does not require sealing and in fact due to the low porosity of the stone, the sealant will not permeate into the stone and will possibly just leave a film on the surface. In terms of cleaning, it is usually sufficient to clean with warm soapy water as porcelain is easy to care for, however do not leave leaves or organic matter to rot on the surface of the stone as this will cause temporary marks which can be unsightly.
Concrete paving, often known as reconstituted stone is manufactured using naturally occurring aggregates, cements and binders. Like any natural material, these can vary in colour and texture between batches, so care should be taken when puchasing concrete paving to ensure all stone is produced from the same batch where possible.
Concrete paving slabs are produced using one of two methods: Wet-cast or Pressed. With wet-cast concrete, the wet mix is poured into a mould and then gently vibrated to remove air bubbles. Wet-cast concrete is generally considered to be a higher end product with a fine finish which can be more ornamental with a slightly rounded or tapered edge. The surface texture may be flat or often formed with a riven finish to replicate the appearance of natural stone. Pressed concrete and made using a semi-dry concrete mix and hydraulically pressed to create a functional yet slightly porous paving slab. Pressed concrete slabs are usually used in utility applications such as shed bases or where a hard standing is required for wheelie bins for example, or for areas where aesthetics are not of prime importance. As such, this paving is more economically priced.
Edge finishes with concrete paving may be straight, chamfered (slightly angled) or tumbled style where the paving is designed to look more rounded, aged or antiqued.
The colour of concrete paving is determined primarily by the natural pigments found in the base aggregates used in construction of the concrete, but also, in many cases, the paving is also dyed to introduce additional colours to the stone. This dye will gradually fade over time. With premium concrete products, the colour is usually introduced by the use of naturally coloured special aggregates which will not fade in the same way as dyed concrete.
When concrete is described as 'natural' colour, this means that no colour dye has been used and the stone will show the colours of the naturally occurring aggregates which is usually a grey or buff colour. This stone colour may vary between batches.
Natural sandstone is a beautiful paving material cut from sedimentary rock. It is available in a range of different colour groups that include a selection of predominant shades in addition to a wide array of other colours found naturally within the rock face formed by nature. The colours may vary between individual slabs in addition to different batches and can be different over time as varying sections of rock face are quarried. Various minerals and natural inclusions will also affect the appearance of the stone. For example, a high iron content may introduce a wider range of brown tones, fossil imprints may appear as black markings and may have occasional leaf prints and quartzite veins may show as white lines within the stone. As with all natural stone, the colours may sometimes be more varied than on other occasions and this variation, sometimes bold and sometimes subtle, is what creates the beauty of natural stone. Colours of sandstone are pastel when dry and richer tones when wet.
As a general guide, the colour ranges are known by their Indian name, from where the majority of sandstone paving is sourced, in addition to the name assigned by the brands themselves when they carefully source and select the stone. Each colour range comes from different areas and quarries. The key colour ranges of sandstone include the following:
Kandla Grey - also known as Promenade, Castle Grey, Pure Grey, Elementary Grey, Mountain Mist, Silver Birch, Fellstyle
Predominantly light dove grey tones and occasional buff and brown shades
Raj Green - also known as Lakeland, Raj Blend, York Green, Forest Glen, Autumn Green, Fieldland
Predominant shades include khaki, grey, cool brown and occasional lilac
Camel - also known as Harvest, Sunset Buff, Sunrise, Buff Brown
Main colours include beige, warm brown, grey and buff
Fossil Mint - also known as Fossil, Mint, Golden Sand, Golden Fossil
Colours usually include cream, buff, occasional bronze, pink, beige and sometimes fossil imprints
Modak - also known as Heather, Modak Rose, Buff Pink
Predominantly peach, terracotta, plum, brown and grey
Autumn Brown - also know as Autumn, Brown Multi
Main shades include cool brown, grey and occasional maroon
Sagar Black - also known as Graphite, Monsoon Black, Raven
Predominant shades include dark grey, light grey, occasional beige and maroon
Raveena - also known as Ravenna, Ravina, Rufina
Main colours include grey, buff, purple, gold, often with heavy banding
Sandstone is a versatile stone that comes in a variety of different finishes from sawn and honed, to sandblasted, traditional riven and tumbled and suits a variety of design styles from contemporary and modern to traditional and period.
It's available in a wide choice of products including paving slabs, driveway blocks, cobble setts, step treads, solid steps, coping and edging and walling bricks.
Like all natural stone, it will exhibit certain imperfections such as dents and small chips, especially around the edges, raised areas and irregular patterning. This is to be expected with any natural product and once laid when the area is seen en masse, will not be noticeable as it's the overall impact that matters.
Limestone paving is a type of sedimentary stone formed mainly from calcium carbonate as a result of the accumulation of shell, coral and algal matter in warm, shallow marine waters. Natural limestone paving has a lightly textured finish and a gentle undulating surface texture. It's generally flatter surfaced than riven sandstone, but is always available in other textures such as tumbled / antique, brushed, sawn and sandblasted. Prior to laying, limestone can be more brittle than other stone types, however this may be alleviated by careful handling and installation techniques. As with sandstone paving, limestone paving is usually sourced from Indian quarries. With all natural stone, the material will contain imperfections and characteristics such as raised areas and dips, quartzite veins and mineral deposits, none of which will affect the durability of the stone and simply highlight the marks produced by nature.
As a guide, limestone is generally available in four main colours:
Black Kadapha - also known as Carbon Black, Midnight, Black Limestone, Torvale, Charcoal, Mystic Sky
This limestone starts off very dark grey or black and gradually lightens in sunlight to become a mix of mid grey tones. To keep the dark tones, use a product such as Pavetuf Back to Black which seals and darkens the paving.
Kota Blue - also known as Steel Blue, Imperial Blue, Flint Grey, Atella
This paving is a blue grey colour and contains occasional copper tones.
Kurnool Grey - also known as Harbour Grey, Grey Limestone, Sylvern, Silver Grey, Dorian
This colour of limestone is less blue grey than the Kota Blue range. It offers a mix of grey tones with very occasional buff.
Kota Yellow - also known as Tuscan, Holton, Bella, Cathedral, Honey Blend, Cotsdale
The yellow ranges of limestone have a combination of shades including warm buttermilk tones, pale grey and occasional ochre tones. When the stone is naturally split with a riven surface, there are more of the yellow tones. When tumbled, the paving tends to have a greyer finish.
Limestone paving, like sandstone, is available in a range of different product types such as paving slabs, driveway blocks, cobble setts and walling bricks. NEVER use acid cleaner on limestone materials.
Slate is a metamorphic rock, usually formed deep below the Earth's surface by heat and pressure. Slate is created in horizontal layers and may contain fossils and small remains of delicate organisms.
Slate paving is predominantly grey in tone and was previously mainly sourced from China, but is more recently quarried in Brazil and India. The Indian slate is the most similar to Chinese slate in terms of its riven surface finish whereas Brazilian slate has a flatter surface profile. As standard, slate paving has sawn edges.
With slate paving materials, the miost frequently seen colours are as follows:
Black Slate - also known as Midnight, Schwarz, Olive, Carbon, Raven
Contains a mix of dark grey tones and a satin finish.
Grey Slate - also known as Green, Silver, Dove Grey, Gris
A greeny grey slate material with a satin finish.
Rustic Slate - also known as Rusty, Copper
A mid to dark grey background with an overlay of bronze, copper and gold in swathes of colour.
Slate is used as a paving material in addition to walling veneer cladding.
Granite is a coarse grained igneous rock comprising quartzite and feldspar amongst other minerals. As a paving material, it is predominantly coloured with flecks of grey, often accompanied by other colours such as pink, creamy yellow tones and sometimes red shades depending upon the chemistry and mineralogy of the stone and the range selected.
Granite paving is very hard wearing and its relatively consistent colour flecked appearance means it works well in a contemporary or formal design style. There is often a sparkle present in sunlight due to the crystals formed during the volcanic heating and cooling of the stone.
With granite paving slabs, the surface is usually sawn flat and even and then either flamed or bush-hammered to give a lightly stippled textured slip-resistant finish. With paving slabs, the edges are sawn. Care needs to be taken when laying granite paving slabs to ensure the stippled face is laid uppermost. Although the smooth appearance of the underside may sometimes seem as though the paving slabs may be laid either way, this is incorrect as the sawn face is not only slippery when wet, but will have unsightly machining marks on the face of the stone.
Granite is also available with a cropped surface in cobble setts. This is a hand-chipped, irregular finish designed to give a rustic appearance. Granite setts are usually available as an approximately 50mm thickness or as a 100mm thick cube which may be used as a raised kerbstone. Granite setts are also available in a sawn and a tumbled finish to suit either contemporary or more traditional settings.
Granite is widely used as a paving material and is seen in paving slabs, large driveway slabs, kerbstones, bullnose step treads, block paving and cobble setts.
Basalt is similar to granite in the way in which it is formed and in nature is often seen in large columnar structures such as a Giant's Causeway. As a paving material, it is a very dark grey coloured stone, quite matte in appearance and with less of the sparkle seen in granite paving.
The usual colours seen in granite and basalt paving are as follows:
Silver Grey - also known asGlacier, Silver Mist, Light
A flecked appearance of grey, white and silver as the predominant shades
Blue Grey - also known as Dusk, Dark, Ebony
A flecked stone with a mix of light grey, blue grey and dark grey tones
Dark Granite - also known as Impala Black, Graphite, Midnight
Dark grey flecked stone with lighter grey tones
Basalt
Similar in colour to the dark granite, but more matte and less flecked in appearance
Porphyry is an igneous rock consisting of large-grained crystals. The term 'porphyry' refers to the purple-red form of this stone, valued for its appearance. Its texture is uneven with a riven surface and is exceptionally hard-wearing and predominantly impervious to staining. Commonly used across Europe and usually sourced in Italy, porphyry paving generally includes rich burgundy tones, grey, green tones and deep ochre and its dark colours make it a practical choice as it hides many stains.
Porphyry paving is most often available with a handcut and a sawn finish and is used for both paving slabs and setts.
Marble is a metamorphic rock made from recrystallised carbonate minerals.The characteristic swirls and veins of many coloured marble varieties are usually due to various impurities that have been mobilised and recrystallised by the intense pressure and heat of the metamorphism.
As a paving material, marble is used occasionally for outdoor projects and is more often found in indoor tiles. The surface when used outdoors is usually smooth to the touch with gentle textures found especially around the veins and patterns in the stone face. occasionally, it may have a lightly stippled texture. For indoor use, the paving is sometimes filled to increase the likelihood of a smooth finish may may be honed or even polished to increase the shine.
Marble has a subtle colour palette with a choice of cream, beige, black or grey tones with a veined or mottled pattern as a distinctive feature. Veins may be a similar tone to the main colour or as seen with the darker shades, a contrasting tone such as white.
The edge finish with marble paving is sawn and occasionally tumbled.
As an outdoor paving material, marble offers a prestigious classic and contemporary style. Its smooth appearance and occasionally lightly pitted surface provides a rich and desirable paving choice where budget is not a concern.
Quartzite is a hard metamorphic rock which started as sandstone before being converted to quartzite through the Earth's natural heating and pressure.
The appearance of quartzite is similar to wood bark and comes in a choice of shades ranging from opaque white to grey or also more earthy tones such as red and brown depending upon the amounts of iron oxide present within the stone. Other colours such as yellow and orange may also appear depending upon the minerals present within the stone and a slight sparkle is usually seen, especially in sunlight.
Quartzite is used as a paving material in addition to indoor tile and wall cladding use. With paving and tiles, it has a sawn edge and either a naturally riven surface or a secondary process such as brushing or flaming may be applied.
Yorkstone is a tight grained, carboniferous sedimentary rock formed in layers over several million years. It is a type of sandstone paving produced in Britain whereas many other, more economically priced sandstone options are sourced from India.
The colours of Yorkstone depend on the minerals in its makeup and vary according to the quarry from which it is mined. As a general rule, Yorkstone can be buff or grey coloured as the predominant shade, but may be a mixture of both and include other colours according to the mineralogy of the stone. Yorkstone is one of the most expensive stone types and stone with a similar appearance can often be found at a much lower price with Indian sandstone, especially that with 'York' in the name.
The texture may be naturally split and riven or have a sawn surface finish and is therefore suited to both traditional and contemporary styled gardens. It is also available as a reclaimed material to suit older properties or restoration work.
Schist is a metamorphic rock meaning it has changed from one form to another due to the impact of heat and/ or pressure from the Earth. Schist rocks have large grains visible to the eye.
Schist paving is an unusual stone and is mainly grey-green tones with white crystal-like banding running throught the stone giving a cloud effect appearance. It is generally flat surfaced with a lightly textured sandblasted finish and sawn edges.
Schist paving is available with matching bullnosed step treads.
Paving slabs (sometimes known as flags or flagstones) are large flattish pieces of stone or concrete used as a decorative hardstanding in a garden or area for domestic foot-traffic and are ideal for patios. Standard paving slabs are not suitable for a driveway. Patio paving is available in a wide choice of materials and styles to suit various colour schemes and personal design choices such as smooth, flat paving typically suiting a more modern style garden whereas as riven, natural finish works well in more traditional designs.
Large driveway slabs are similar in appearance to normal paving slabs for patios, but are manufactured to a thicker depth to make them suitable for domestic vehicular use. They are typically found in granite paving in addition to porcelain; the latter is often specially constructed in many ranges to have a concrete backing enabling the paving to be laid on an MOT Type 1 + sand bed, the same as block paving, which is a quicker installation process.
Indoor tiles are often made in the same ranges as exterior paving, but generally with a more refined and lower slip resistance surface finish. Indoor tiles are usually much thinner than exterior paving at around 10mm +/- and unless stated to the contrary, should not be used outside.
Block paving is a product designed primarily for driveways and is based on the principle of small blocks of stone that are laid on an MOT Type 1 + sand bed and simply pushed close together to enable each block to hold the adjacent blocks in place. With concrete block paving, there are often small locating nibs on the sides of the blocks to enable each block to 'lock' into place against the next stone, but with natural stone blocks, there is far more tolerance on the dimensions of the stone and more care has to be taken during installation to make minor adjustments in the sand bedding to accommodate these tolerances. When laying blocks, the perimeter must be laid on a mortar bed and haunched up to ensure the edges are set firm and then the centre blocks should be laid on sand as described above.
Concrete block paving is available in different thicknesses for different purposes. 50mm thickness is suitable for most domestic driveways, 60mm is more heavyweight and designed for larger or heavier vehicles and 80mm is used in commercial settings. Natural stone block paving is nearly always 50mm thickness, but with a tolerance on dimensions.
There are various design choices in block paving, from standard rectangles in a uniform finish, to blocks that resemble aged cobble setts. Natural stone is available in sandstone, limestone and granite materials and the natural characteristics of these options offer a gentle colour variation which is easy on the eye, especially over a large area.
Block paving as standard does not allow significant water to permeate through the stone and there is an option to use 'permeable' block paving instead. This is constructed with a toothed edge that allows water to soak between the stones, however it must be installed as part of a SUDS system. This is a series of specific sized and shaped aggregates applied in layers under the permeable blocks to allow water to percolate through in an effective way, preventing surface water from running onto the public highway. In most cases however, if surface water is directed to a soakaway within the grounds of the property, removing the risk of water entering the public highway, the necessity to use permeable paving and a SUDS system can be avoided. It is recommended that the local planning officer is contacted for advice to ensure the project conforms to the correct regulations.
Cobble setts are small square or rectangular pieces of stone suitable for many uses such as edging a patio or lawn, making an interesting pathway or in many cases, using on a driveway. Unlike block paving, cobble setts require laying on a full mortar bed, similar to laying paving slabs. When using around the edge of a lawn or patio, it's necessary to haunch up the edges of the setts using mortar to ensure they are securely set in place.
The sizes of cobble setts are typically 100mm x 100mm or larger and are available in a choice of materials such as sandstone, limestone and granite. They are often handcut meaning they are irregular in dimension which adds to the rustic charm of this type of product. Others may be sawn for a contemporary uniform finish or tumbled to give an aged appearance.
Clay pavers are attractive brick-like paving materials suitable in many cases for driveways and also used frequenty on pathways or within courtyard style gardens. Unlike concrete block paving which can fade over time, clay pavers weather well and have a rich palette of earthy colour tones to choose from. Clay pavers that are suitable for driveways can usually be laid either on edge or 'on bed' - the latter gives the greater coverage. Some clay options are too soft for driveways, but look great in courtyards and paths. Clay is most often laid on an MOT Type 1 + sand bed, the same as block paving.
These features are ideal for use within a patio design or as a standalone feature elsewhere in the garden. They most often comprise a series of concentric circles made from individual sections of stone and are sold by the diameter of the paving circle. In some features, there is a 'squaring off kit' which is a further section of stone that is added around the final outer ring of the circle to make the kit a square shape. This is ideal when integrating within a patio where all the slabs are rectangles or squares as otherwise these would have to be cut to accommodate the circular shape. Some squaring off kits completely enclose the circle whereas other comprise corner sections to transform the circle into a square. Check the measurements of both the circle and the squaring kit if dimensions are of prime importance.
If a larger circular kit is needed, these can often be made to order, so be sure to enquire with us about this. Another option is to increase the size of a standard circle using cobble setts around the perimeter. By using 100x100 cobble setts around the circle, each ring will increase in size by 20cm diameter and this not only provides a suitable solution where the circle gradually increases in size, it is also an attractive style feature.
Circle outer rings are single rings and re ideal for positioning around a feature such as a pong, water feature or planting bed.
Step treads are the main horizontal section of the step that is walked on and these are often bullnosed on the front edge for an attractive and durable finish. There are many options to choose from and all will have paving slabs to match. In natural stone especially, they are constructed from thicker stone than the corresponding paving slabs. With porcelain paving which is made in batches, step treads are usually made to order to ensure they are produced from the same batch as the paving material. Be sure to enquire about these if required.
Steps on the other hand are made from solid sections of stone and are the complete step unit, not just the top plate. They are usually hollowed out underneath to make them manageable to move and work with and are made primarily from natural sandstone.
Walling bricks are made from either concrete or various natural stone options such as sandstone and limestone. With concrete bricks, they are mostly consistent in dimensions and may be laid quite easily in the same way as constructing a wall using house bricks, however with natural stone blocks which are often irregular in dimension, this requires careful craftmanship to build a wall as allowances need to be made to work with the dimensional tolerances. With natural stone walling bricks, they may be laid with either the side of the brick facing outwards or, for greater coverage, it is often an option to lay with the top face outwards.
Many natural stone products are handcut giving a rustic and irregular appearance and some are tumbled for an antique style finish. Many concrete walling bricks are constructed in the style of natural stone which is far softer in appearance than a house brick style when used in a garden setting.
Wall cladding is a sectional veneer used to cover an existing wall. It's often made using small sections of natural stone adhered to a backing plate that can be bonded to existing brickwork (as long as it's of good quality construction) to create a stylish and original feature wall. The sections can be cut to size as required. Similarly, there are porcelain wall cladding options offering a similar appearance and again, available as individual tiles for bonding onto a wall. Both types of wall cladding can be used as an ideal solution for covering an unsightly wall and work equally well both indoors and out.
Wall coping is a section of stone used on top of wall to finish off the top edge leaving a tidy, usually flat surface. Most walls are either single or double brick with and wall coping is made into two different widths to accommodate wall thickness. In many cases it's quite possible to use paving slabs as wall coping or of it's only viewed from one side, then bullnosed step treads can also be used (these are only bullnosed along one long edge).
All paving products sold by Paving Superstore are tested and conform to UKCA standards and hold a Declaration of Performance Certificate. This sets us aside from many other websites and guarantees you are buying a quality product designed to last. Let us tell you a bit more:
It is a legal requirement
Strict EU regulations were introduced in 2013 to ensure all paving sold in the UK meets the minimum standards set out under European standards EN1341 (flagstones), EN1342 (setts) and EN1343 (kerbs), however MOST companies selling paving online DO NOT adhere to these legal requirements as it is not heavily policed by Trading Standards. ALL paving products sold by Paving Superstore are manufactured by leading brands and DO meet these standards. All products are CE marked / UKCA / UKAS accredited. UKAS is the National Accreditation body for the United Kingdom appointed by the government to ensure products meet the high standards needed to attain certification. All products also hold a valid Declaration of Performance certificate which details the tests and results for each of the necessary criteria which guarantees you that the products we sell are fit for purpose.
Test Process
The water absorption test measures the amount of water a stone can hold when fully saturated. This is expressed as a percentage of the total weight. So, a result of 1% means that when fully saturated, 1% of a stone’s weight will be water. As a guide, paving such as porcelain is usually less than 0.5% porosity, granite is around 0.5%, sandstone and limestone are in the region of 1-3% and concrete, 6%
Why is this important?
This is an indicator to how quickly stains will soak in and how quickly a stone will look dirty. The lower the number, the better it will deal with staining. Obviously other factors such as colour and texture will also play a part in the likelihood of staining. High levels of water absorption are also associated with increased algae growth which is known to be a problem with poor quality stone as this is often more porous as a result of it being an inferior standard.
Test Process
Frost resistance testing is called the Freeze/ Thaw test and is conducted by repeatedly freezing the paving to -40 Fahrenheit and then thawing it, before repeating the cycle again. During this process the paving will lose some of its flexibility and the key to good quality paving is that it does not lose a high level of resilience during the test cycle. Losses in Mpa should not exceed 5 Mpa
Why is this important?
with very low temperatures. Paving which is overly porous will crack in frost and it is essential that paving is tested to the above standard to be sure it can cope in all weathers.
Test Process
The ‘flexural strength’ test shows how much bending a paving unit can be put under before it breaks. This is an important test measurement for paving, but not really for setts or blocks as they are not large enough to bend. The test data is normally expressed in mega pascals (Mpa) with higher numbers being better. A typical measurement with sandstone is over 13 Mpa, concrete 5 Mpa and porcelain is often over 40 Mpa
Why is this important?
The flexural strength is important as it ensures the paving is not overly brittle which would cause difficulties when handling and laying.
Test Process
The ‘compressive strength’ test shows how much a stone can be squashed before it breaks. This is most important for setts and blocks as these are often used on driveways. It’s expressed in mega pascals (Mpa) with higher numbers being better.
Why is this important?
The compressive strength rating is important when deciding on stone suitable for a driveway or commercial setting where excessive weight will be applied to the paving. Paving that does not pass the required standard will not support any excessive loading.
Test Process
Slip resistance testing is a complex and varied area however the two main tests for domestic paving are either the pendulum test (PTV) or the ramp test (R rating). With the pendulum test, a pendulum is swung over the surface of the stone which will slow it down. The rougher the surface, the more it will slow the pendulum and the higher the value (PTV). It is tested both wet and dry. The lowest permitted value for external use when wet is 36.
The ramp test (R rating) is often used for porcelain paving and this is conducted using a ramp which is gradually raised. Oil is applied to the ramp and a test person walks onto the ramp wearing boots. The measurement is taken from the point at which they slip. R11 is the rating usually applied to porcelain paving and this is equivalent to the value of 34 to 51 in the PTV test data (pendulum test value).
Why is this important?
Ensuring paving has good slip resistant qualities is important for outdoor usage, especially when used by children or elderly people. There is no point installing stone that does not meet the specified criteria for outdoor surfaces as it will be dangerous and not at all suited to purpose.
The following table shows the slip test data ratings for both test types and the recommended usage for paving conforming to each result.
Further to stringent test procedures, all paving sold through Paving Superstore is ethically sourced with all manufacturers belonging to the Ethical Trading Initiative or alternative schemes. This promises that:
- employment is freely chosen
- child labour will not be used
- discrimination shall not be practised
- living wages are paid
- employees are treated respectfully and fairly
- safe and hygienic working conditions are provided
- working hours are not excessive
Please ensure you only buy ethically sourced natural stone
MOT Type 1 is an aggregate used as a sub-base for paving as it stabilses the ground and allows for drainage. It is tested by the Ministry of Transport (Departmant of Transport) as a surface that remains stable under extremes of temperature. When laying paving slabs for a domestic patio, MOT Type 1 is applied to the excavated ground and then compacted with a wacka plate (a motorised tool that applies impulses of pressure to significantly compact the ground) to a final compacted depth of 100mm. For a driveway, the compacted depth should be a minimum of 150mm and is usually levelled with a vibrating roller. MOT Type 1 can be made from a variety of different materials such as crushed limestone, granite or concrete and if the material is classified as MOT Type 1, then it will be suitable as a paving sub-base. Approximate coverage rates are as follows:
-Patio paving - 1 x bulk bag will cover approximately 5 square metres (used at 100mm compacted thickness)
-Driveway paving - 1 x bulk bag will cover approximately 3.5 square metres (used at 150mm compacted thickness)
All paving slabs and cobble setts should be laid on a full mortar bed comprising sharp sand and cement using a ratio in the region of 3 parts sand to 1 part cement (a weaker mix up to 6 to 1 ratio is suitable in most cases, especially where a permeable jointing compound is used). It is imperative that the mortar is laid fully under the paving and not simply in spots (sometimes known as the 5 spot method, like the number 5 on a dice) as when the paving dries, the spots will show through the surface of the paving. Furthermore, a full bed ensures the paving is thoroughly supported and prevents water ingress which will weaken the installation. As a guide, the mortar bed should be laid at a depth of 50mm for most paving slabs. When using a 3:1 ratio of sand to cement, the following approximate coverage is achieved:
-Patio paving - 1 x bulk bag or 40 polybags of sand will create a bedding mix suitable for approximately 15 square metres of coverage
-Driveway paving - 1 x bulk bag or 40 polybags of sand will cover approximately 11 square metres (used at 50mm compacted thickness)
-Patio paving bedding mix - 16 x 25kg bags of cement combine with 1 x bulk bag of sharp sand to cover approximately 15 square metres
Priming slurry is a polymer and cementitious compound used to help paving slabs adhere to the full mortar bed and may be used on most types of paving, but is essential to use with porcelain paving which has a low ability to adhere to the mortar bed owing to its low porosity. Slurry such as Pavetuf Priming Slurry should be pasted onto the back of the slabs prior to positioning onto the wet mortar bed.
A screed bed is a layer of sharp sand (sometimes grit instead) levelled off across the surface of the MOT Type 1 sub-base in readiness for laying block paving driveway stone. The perimeter stones are always set in a mortar bed and the centre stones are laid onto a sand screed bed and then compacted into place using a wacka plate. Some porcelain driveway slabs such as those with concrete backing are able to be laid onto a screed bed and this is a quicker installation method than laying on a mortar bed. This method is not suitable for permeable block paving as this requires a series of specific different sized aggregates to be used under the blocks instead of sand. Specific guidelines may be found here.
Jointing compound may be used as an alternative to jointing between the slabs with sand and cement. Products such as the Pavetuf Jointing Compound and GftK VDW840N are also known as polymeric sand and are quick to install and set hard in the joints. The traditional method of pointing with a wet sand and cement mix and trowelling the mortar into the joints and pressing into shape can be time-consuming and can only be undertaken in dry weather. With jointing compounds, these are applied by brushing into the joints whilst ensuring the area remains completely wet. Once left to dry, it sets hard. This is much quicker and the work may be undertaken in both wet and dry weather conditions.
Natural stone and concrete paving is usually cut with a diamond blade disc cutter. Porcelain paving on the other hand, must be cut with a specialist porcelain blade and a wet cut to ensure the paving does not overheat or vibrate which will cause it to break.
There are two main types of paving sealant: topical polymer based sealer and impregnator sealer. Polymer based products are the older type of sealant and create a protective film over the surface of the paving, however this type of sealer cannot be used for at least six months after laying the paving as it is not breathable and will cause moisture and the natural salts within the mortar to become trapped under the sealer leaving a white cloudy film on the surface of the stone. Furthermore, it will not wear away evenly and quite often peels away from the surface which may require chemical or mechanical removal.
Impregnator sealer on the other hand is breathable and may be applied straight after laying the paving as this will continue to dry even once the sealer has been applied. With impregnator sealer, this soaks into the stone and fills the small capilliaries to prevent stains from soaking into the stone, instead leaving them on the surface to be wiped away. With impregnator sealers the finish of the product can be invisible offering protection, but without affecting the appearance of the stone, or satin, leaving a slight sheen.
The Pavetuf and Lithofin paving cleaners are industry leading products. There are general cleaners for light marks, deep cleaners for more stubborn stains and more specialist cleaners for specific types of marks. These include green off or algae cleaners for removal of organic stains, rust removers for gradual lessening of brown iron oxide marks that may appear naturally within natural stone and salt erasers for removal of efflorescence (salts that appear as white marks in both natural and concrete paving due to high cement content in the product or the mortar reacting in certain atmospheric conditions). Acid based cleaners used to remove mortar overspill on brickwork is NOT suitable for most natural stone products as it will cause iron content within stone to rust and will also take the colour out of stone such as black limestone.
Other Terminology
Tongue and groove board is used in high quality building construction and is often used for the roof or floor. It is a smooth, planed interlocking timber board.
OSB is the acronym for Oriented Strand Board, also known as waferboard, sterling board, exterior board and smartply. On many products this is also known as solid sheet when describing roof and floor. It is an engineered wood product formed by bonding laters, strands or flakes of wood together to form a sturdy board.
This describes the cladding on the walls of the building. Overlap cladding is formed by a series of timber panels overlapping the top of the section below. Overlap sheds are generally more economical than shiplap sheds.
Shiplap cladding is formed by a series of overlocking boards as the side walls of the shed. This is generally considered a better construction than an overlap shed.
Pressure treated wood has had a liquid preservative forced deep into the grain of the wood to protect it against deterioration caused by weathering and insect attack. The process requires the finished timber product to be placed in a large vat containing timber preservative. The vat is sealed shut and the air removed from the container forcing treatment into air pockets within the wood. This creates a deeper treatment than a painted version and offers a longer term lifespan of the product although it is recommended that annual paint on treatments are applied to the product to further protect it against the elements. Pressure treatment can leave a blue / green residue on the surface of the wood which will gradually weather off, however if preferred, the surplus treatment can be either pressure washed off or removed by lighty sanding the affected area.
Dip treated wood has been coated in a light factory-based treatment to protect it during storage prior to sale and whilst in transit. The building or structure will need a further treatment with a good quality wood preserver as soon as possible after delivery.
Some timber products are untreated prior to installation. This is standard practice with products such as log cabins as the wood is required to swell slightly between the interlocking boards to create a weatherproof seal. Once erected, the building will need treatment with a good quality wood preserver and a program of annual treatment undertaken thereafter to ensure the building remains protected.
An apex roof forms a peak at the top of the building meaning the central walkway through the building will be the highest point.
A pent roof slopes from one side of the shed or building to the other and often (but not always) the door will be on the front of the building where the roof is the highest.
Vinyl coated metal sheds are of a sturdy construction as they are built from steel and then coated with a protective and visually appealing wipe-down vinyl surface. These buildings are rot resistant and need little maintenace. Some have anti-rust and anti-fire properties.
Powder coated steel is an attractive painted metal that is used for garden buildings in addition to the frames on some furniture. Care should be taken to repair and repaint any areas where the paint becomes damaged or wears off over time as the exposed metal will rust.
The dimensions of decorative aggregates are a British Standards BS EN933-1 measurement formed as part of the stone grading process. This process requires all stone to enter a series of sieves set to a specific measurement and stones of the correct size will fall through to the relevant layer. This means that some larger stones may fall through if they meet the required measurement in one direction and the sieve allows the pieces through. The measurements stated are therefore to be used as a guide only.
