Pavestone's Paving Installation Guide
Forward planning will undoubtedly save you time later on in the project. Having chosen your Pavestone product we suggest you take a piece of paper and mark the outline of the area to be paved. Try to design your project to incorporate sizes of paving that will eliminate the need for too much cutting. This plan will be a useful guide both when ordering and laying. When constructing, remember that when building a patio or path close to a house it is important that the finished paving level is at least two brick courses (150mm) below the damp course. Always provide a ‘fall’ to drain water away from buildings (a gradient of 1:40 is usually sufficient). Some of the tools you will need in undertaking a project :- Rake, shovel, tape measure, bricklayers trowel, tamper, spirit level, wheelbarrow, stringlines, soft brush, timber straight edge, mixing board, mallet or hammer and a bucket.
Preparing the ground for paving depends upon site conditions and the intended use of the paved area. If your ground is firm, you probably need only remove the turf and topsoil to a depth to accommodate the 30-40mm sand bed plus the slab and mortar thicknesses. If the subsoil is wet or spongy you need to dig out much deeper to put in a stabilising layer (approx 100mm) of well compacted hardcore (often called MOT, scalping, crushed hardcore) before laying the sand bed, again allowing for 30-40mm of sand plus the slab and mortar thicknesses. In reality, few areas are already level enough for immediate paving, so some areas need to be excavated whilst others need to be made up with compacted hardcore. The use of hardcore helps ensure adequate site drainage, which is a prerequisite for paved areas.
Examples below are a guide line only and depending on ground conditions, intended usage and the type of paving to be laid may be subject to alterations: Most garden situations - light pedestrian use, solid established ground: Bed of mortar on 30 or 40mm compacted sharp sand, heavy domestic use - to take heavy mowers, support planters, maybe on less stable or wet ground: Bed of mortar on 30 or 40mm compacted sharp sand on 100mm compacted hardcore.
Terracotta Tiles and Natural Stone - Use 25mm wet mortar bed on 30 to 40mm compacted sharp sand (note that a hardcore foundation as per b) may be required according to ground conditions)
Car driveways - Block Paving is recommended rather than paving stone. However if Paving Stone is to be used then this should only be undertaken using a 100mm wet concrete bed on a suitably compacted hardcore base.
Construction of the Bedding Course
This work should never be undertaken in wet weather. Bedding sand is spread over the area in a loose non-compacted layer, slightly in excess of the finished depth. (1) A vibrating plate compactor is used to compress this layer which is then screeded using screeding rails (2), to the required level. The area of bedding course to be maintained in advance of the placement of pavers, is normally up to 40 metres square. Only prepare the bedding course area which you will lay in one day and protection of an unlaid area is essential, when left overnight or before the onset of inclement weather. The bedding sand is now ready to start laying the pavers. Once prepared, the compacted bedding course should not be disturbed.
Laying the Pavers
- Stack unused pavers approximately 1 metre back from the advancing face.
- Check pattern regularly with string lines.
- Do not impose undue loads on to un-compacted pavers.
- Do not stand too close to “edge” of paver line. Set pavers about 10mm proud of edge restraints which on compaction will leave approximately a 5mm chamfer proud of the surface.
Pavers to be cut should be handled carefully and cut using a specialist cropper (4) which can be hired, or a diamond saw. Care should be taken to wear recommended protective equipment.
Joint Filling and Compaction
Always use kiln dried paver sand to finish off the job. The sand is spread over the surface and then brushed into the joints. Surplus sand is removed and the vibrating plate compactor (with rubber mat installed) is then passed over the pavers two or three times (5). If an unfinished area is being compacted, the compactor must only go to within one metre of all unrestrained edges. The pavers are normally compacted to the required level after two or three passes. After this the whole sequence is repeated until all joints are full. (6) All surplus sand is now removed and the area is ready for use.
Critical Points to Remember
The end result is only as good as the sub-base, so only use M.O.T. Type 1 or approved Granular Sub Base (GSB). Sub-base levels must be formed to required final profile. Use restraints to achive this.
- Use Zone 2 concreting sand for the bedding course. Compact to correct levels. Construct a trial area in advance.
- Start from a straight edge. Always use and frequently check string lines. Place pavers maintaining 2-5% joint.
- Use kiln dried paver sand for joints. Take care when cutting. Do not over load until compaction of interlocking sand has been completed.
Laying Paving Flags
Remember to select paving from different packs as you go along. This enables colour blending and will help to alleviate any shade variations that may occur between packs, giving your design a “Natural” look.
Pavestone strongly recommends sealing the underside of natural stone paving prior to laying with a PVA sealant. This will deter the possibility of surface staining on the flag face which can be caused by the drawing up of salts from the cement through more porous stone such as Fossil.
Depending on your ground type (see Site Preparation and Foundation section above) use a mixing board to make up a slightly wet mortar bedding mix of 1 part cement to 5 parts of building sand.
Peg out several string lines so as to establish the desired level of the patio incorporating a slight fall for water run off for drainage. Start flag laying from a corner or straight edge.
Pavestone recommends that each paving flag is individually laid on a full mortar bed and that the 5 spot method is not adopted (See below). The full mortar bed method enables any variation in thickness of individual slab to be taken up.
A full mortar bed to cover the base of the flag is placed over the sub base, the flag laidchamfered edge down if it has one and tamped level to follow the string line with a rubber mallet. Double check alignment with a spirit level and once happy, move onto laying the next flag repeating the process. Continuous checking of levels and falls should be on-going during the laying process and should be taken across the top surface profile of a number of slabs. Before proceeding too far, it is important to equalize slab spacing, gently shuffle the slab with a twist of the trowel until the joints look even.
Because Pavestone products come in a variety of shapes and sizes cutting can be minimised. If your project involves a lot of cutting we advise the hire of a powered cutting tool incorporating a diamond tipped blade (advise the hire shop of what you are intending to cut, and ensure that a suitable diamond tipped blade is selected). Its use will ensure accurate clean cuts are achieved but please use with care and also make sure that your hire shop issues you with full instructions and relevant safety equipment including goggles.
You can use small pieces of wood as 10-15mm thick spacers to help get each slab equally distant from the others but remove them straight after laying. Do not walk on the paving for at least 24 hours. (7) The joints should then be pointed as soon as possible but not if rain or snow are forecast. As with all natural stone products from Pavestone, we recommend that paving is laid allowing for a minimum 10-15mm joint. We recommend joints are pointed using a wet (but not sloppy) cement mortar mix to produce a more permanent waterproof finish. Do not leave unpointed for more than a few days. You must not attempt to brush the mix across the surfaces of the slabs as any cement left on the slab will result in unsightly staining and will often mean a complete renewal of products. Care should be taken not to use too wet a mix and any mortar spillage should be immediately removed with a clean damp cloth or sponge. All joints should be jointed using a special jointing tool (available from builder’s merchants) or with a suitably rounded piece of wood, to a depth some 5mm below the adjoining paving surfaces (8).
Sizes and Joint Widths
All dimensions quoted are nominal and are for guidance only. Actual sizes will vary. Pavestone highly recommends dry laying natural stone paving prior to commencing full installation of the project to satisfy that planned paved areas and features such as circles meet with the installers satisfaction. The nominal paving sizes and quoted usually allow a nominal 8-14 mm joint width. When laying random paving and circles with their fettled edges joint widths may, depending on the paving type and laying pattern chosen, vary between 8mm to 25mm.
The '5 Spot' Laying Method - Not Recommended by Pavestone
The '5 spots' of mortar method of laying paving is not endorsed by Pavestone or recommended by professional landscapers and can cause significant problems once the job has been completed. Voids can fill with water and can create subsidence or instability in the finished patio. The resident water pools under the paving can cause staining in the face of more porous paving such as Fossil Sandstone. Voids are created beneath the flags which can cause them to fracture when loaded through lack of support. The voids can become infested by insects or burrowing animals which can again create subsidence or instability in the finished patio. The mortar spots are more likely to promote flags to rock when traversed.