Flagstones and setts from Natural Paving are of the highest quality and will give you years of trouble-free service when laid properly. All paving should be laid to a level that is at least 150mm below the Damp Proof Course (DPC) of any adjacent buildings.
Mark out the area to be paved, allowing 100-300mm working room at the edges. Dig down to remove any vegetation, topsoil or loose material. Where ground is poor, it’s better to dig down further and then build-up the levels using crushed stone. When working against a wall, the brickwork may act as a level guide, but for open spaces, a taut string line should be used. Use a spirit level to set the line as near to ‘level’ as is possible. Next, move one end of the string down by 15mm per metre of paving. So, if your paving is to be 4 metres wide, then move the string line down by 60mm (4 x15mm). This will give adequate fall to drain the paving once it’s completed.
As natural stone varies in colour and texture ensure you have enough product on site to complete the project and always mix the product from all the packs during installation. This will minimise the effect of colour banding. Flagstones must always be laid on a “full bed” of sand and cement that supports the whole flag and not just the corners. Use 6 parts of sharp sand or all-in ballast with 1 part cement. Mix together and add just enough water to make a mixture that binds to a sticky consistency: a good guide is that there should be sufficient water to allow the mix to be moulded into a ball without falling apart, but not so much that water would run out of it were it to be squeezed in the hand. To improve adhesion, consideration should be given to applying a PVA and water solution to the underside of the flagstones prior to bedding. Spread a layer of bedding mix that is roughly 50mm thick. Place the first flag onto this bed and use a rubber mallet to carefully tap it down until it is at the correct level. Place the next flag adjacent to that just laid, leaving a joint width of 15-20mm and again, tap down to level. Repeat this process, laying one flag at a time until the whole area is covered. The joints of flagstone paving look best when pointed with a mortar. Make a pointing mortar by mixing 4 parts washed sharp/rendering sand with 1 part cement. Again, add as little water as possible to bind the mortar without overwetting it. Feed pointing mortar into empty joints from the edge of a trowel and use a pointing bar to press it down firmly and to polish it when the joint is full. Wash off any excess mortar from the stone before it dries.
Try to keep off the new patio for the first 24-36 hours, by which time the initial set of the mortars should be complete. After 5-7 days, the patio should be fine for full use.