Slab Laying Guide

Checks

Always check the slabs when delivered, any faults, blemishes or quantity issues should be reported and rectified now.Also check that the area you want slabbed is free from any pipe work, drains, cables etc. If any of these are an issue you need to prepare and take measures beforehand to overcome this.

Ideal tools needed for the Job

Gloves, a Mask if you need to cut the slabs, a Sprit level, a Trowel, a Rubber mallet, String or straight edge, spacers to maintain even gaps between the slabs and a pointing iron or similar.

Preparation of the foundations

Preparation is important. Please take time to plan the slabbed area. If needed use some graph paper to draw out the dimensions of your patio and use this to plan where different size or coloured slabs are to be placed. You need to make sure the ground is level and if near to a house ensure there is a suitable fall of about 1:40 to allow rainwater to drain away from the house. Check your levels The finished slab surface must be at least 150mm / 6 Inches below the damp course on any adjacent walls. The foundations will be dependant on ground conditions and the expected use. For paths and patios with firm foundations and with light use a layer of 40-50mm of compacted sharp sand may be adequate, but for all other purposes and for heavy use you will need firmer foundations. For ground that is less firm you may need to prepare 100mm of compacted hardcore under the sand. You will need to increase the depth of compacted hardcore to 150mm for driveways.

Laying the slabs

Set out, prepare and dig out the area to the required depth. Ideally stack the slabs carefully near to the prepared area. If you are mixing slabs with different colour blends or slabs of different sizes, work out what percentage mix you want and prepare this before you lay the slabs. We recommend that when laying the slabs you should lay them onto a full bed of mortar, using the following mix of 1 part cement to 5 parts building sand. The mortar mix should only be slightly wet; it should only be damp enough to make a ball in your hand. Too wet a mortar and the slabs will sink and not have a strong enough base to last, too dry a mortar and you will have problems with laying them level and the slabs will separate from the mortar base over time. This is important, so please check the water content. A minimum bed of 25mm should be used for each slab, and tapped down level with a rubber mallet. You can use a trowel to draw the mortar part way up the side of the slab to save time on the pointing later.   You may find it useful to use a string line to help with the placing of the slabs and with the level and fall. Keep checking the levels as you work. For a more professional finish you should use spacers between the slabs, this ensures the pointing widths are consistent, depending on your preferences, but ideally, a 10mm gap provides the best finish.

Pointing

Do not walk on the paving for at least 24 hours after they have been laid the mortar needs time to set. Once it has set you can start to point around the slabs. Avoid pointing them if the slabs are wet, the cement can stain the slabs and this is very difficult to remove. There are many methods of pointing, depending on the slab type and your desired finish. A basic pointing method is to prepare a mortar mix of 1 part cement to 4 parts building sand; again the mix should only be damp and not wet. Work the mortar mix firmly into the voids between the slabs to create the finish you require. For the best finish a pointing iron should be used or something smooth and small enough to fit into the void between the slabs, make sure the joints are clean and free from debris, wipe away any excess mortar from the slabs without disturbing the joint and leave the mortar mix to set. Always allow the mortar mix to set completely before any cleaning and sealing of the slabs.