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How To Lay Natural Stone Paving

30 September

Choosing natural stone paving for your project is both a practical and aesthetically pleasing solution. In this article, we’ll take a look at pre-planning and fixing your slabs, taking into consideration the substrate, what lies below your paving, and guidance to make your installation successful.

Classic Autumn Umber Sandstone Paving
Whether you’re laying your paving for a patio, driveway or path, laid using best practice and the correct tools and materials, natural stone paving such as our Classic Autumn Umber Sandstone, with a little regular maintenance, will serve you well for many years.


If you have purchased sandstone, limestone, or granite paving, the process and procedures are the same i.e. prepare the area, lay the substrate, setting out, cutting, fixing, and sealing.


Image: Classic Autumn Umber Sandstone Paving


Checking your delivery


Before starting to lay your slabs your order should be checked for the correct quantity and quality. It’s likely your natural stone paving has travelled thousands of miles to reach you, therefore it is commonplace for a few pieces in each crate to be damaged and not whole. It’s standard industry practice to use these slabs where a part slab is required, such as to the edge of an installation where a whole tile is too large and requires cutting. This is known as a “cut”.


What tools will I need?


A professional landscaper would use the following list of tools for your paving project:


• Gloves and goggles for safety
• spade and shovel
• Wheelbarrow
• brick trowel
• pointing trowel
• lump hammer
• bolster chisel
• rubber mallet
• long spirit level
• string line
• line pins or stakes
• soft brush
• tape measure
• straight-edge timber
• small cement mixer
• plate compactor (‘wacker’ plate)
• an angle grinder or petrol saw.


However, it would probably be more appropriate for a DIYer only planning a single project at home to hire the larger powered equipment, rather than have it gathering dust in the shed.


Setting out

Classic Honeymead Sandstone Paving

Do a dry run – this is laying out slabs to give you the best aesthetics and the most practical layout in terms of keeping the need to cut slabs to a minimum.

Paving should be laid at a level that is at least 150mm below the damp proof course (DPC) of any adjacent building except where level access is required at a doorway (eg: for disabled access). If working against a building, it may be possible to use the horizontal brickwork jointing as a guide to level. Alternatively, a taut string line or a temporary chalk line can be used as a guide.



Image: Classic Honeymead Sandstone Paving

Drainage


To avoid rainwater forming puddles on the patio, and potential damp problems inside the property, the patio needs to be laid sloping away from the house so that rainwater can drain away. This may be by including a purposeful gully or drain into the project or simply a drop off into the garden.

The industry standard for the fall of natural stone paving is a ratio of 1:80. This means that for every 80 units of distance, the level must drop by one unit. For example, a patio which runs 4 metres from the house, will have to drop by 4000mm divided by 80, which is 50mm.


It’s all about the base


All paved areas, whether they are used as driveways, paths or terraces, require a stable base. Every project site is different and a judgement will have to be made at the start of the project as to the long term stability of the existing ground.

Please bear in mind that it is always best to err on the side of caution and lay a stronger base at the outset than have to lift and reinstate a sunken area in the future.

Laying where the bottom sub-base is earth, the following system can be utilised:

1. On top of the earth consider laying a ‘capping layer’ of crushed limestone if the earth is particularly silty – this should be well compacted.
2. Next consider laying a membrane to prevent upward migration of fine soil particles.
3. Next is a granular layer of Type 1 MOT which is compacted using a “wacker”.
4. Mix for fixing – purchase a prepared mortar mix or blend your own cement and sharp sand. A 4 to 1 mix of sand to cement is sufficient. A purposeful outdoor tile fixing adhesive is also a suitable alternative.

 

Gap between the slabs

Classic Silver Grey Sandstone PavingGenerally, the gaps between natural stone slabs is between 8-15mm. This variation is mainly due to the undulating hand-cut edge of most natural stone paving. If you have a straight-edged slab then a joint gap of 5mm is considered more aesthetically pleasing.

The joints can be filled with the mortar mix used for fixing which is applied with a trowel. Filling joints with a mortar mix is the traditional method often best suited to paving projects on older period properties to maintain the authentic look.

To fill the joints, mix four parts sand to one part cement, making up the mortar mix in small quantities, say one 25kg bag of sand at a time, because pointing is a slow process and the mortar has a fairly short working life (20-60 minutes depending on time of year). Aim for a mortar mix that has a workable but flowing consistency, something similar to the mix for a cake, which forms ‘peaks’ without slumping too much.

Adding a plasticiser to the mix makes the mortar far more workable. It is worth noting that some bags of cement contain a built-in plasticiser, so there is no need to add one to the mix - check the packaging on your cement.

The other option is a purposeful jointing compound that is brushed in, which is a quicker solution than the traditional mortar mix. Available in a variety of colours, sweep-in jointing compounds can be applied in all weather conditions, and once set are ‘crack-proof’ and ‘frost-proof’ due to their polymer ingredients making them flexible.

Jointing compounds can cope with gaps from 3mm wide and 25mm deep. Jointing compounds are easy to use and simply require you to soak the paving with water before commencing and then sweep the jointing compound into the joints.


Getting a good fix - compacting the paving


When first positioned the paving will sit proud of the already laid slabs and will need to be tapped down to the correct level. This steadies the paving, ensuring it lies flat and is evenly supported, as well as ‘keying’ it to the fixing material.

Once the paving is in the correct position, taking into consideration the joint width, it should be tapped down using a rubber mallet until it is at the desired level. Best aim the blows at imaginary points that are halfway between the centre and each corner of the paving stone, and use firm but not heavy blows to ‘encourage’ the stone to settle to the desired level.

If the slab refuses to go down to the required level, then it is better to lift the stone, scrape out some of the excess bedding and re-lay rather than risk breaking the stone by hitting it with too much force. However, if the paving stone goes down too far, then lift it and apply more fixing material.


Checking if the stone is laid correctly


Once laid, paving stones should be sound and stable, that is they should not ‘rock’ from side to side, and there should not be any ‘lips’ from one slab to those laying adjacent, which could be a dangerous trip hazard.

Check surface levels and profile regularly as you go by standing back and making a visual inspection. Maintain accuracy by using a long spirit level or a straight-edged length of timber to ensure adjacent paving slabs are level. Lifting slabs to refix them is never fun and is time-consuming, however, it’s key to correct any problems at this stage whilst the fixing compound is still wet, it is much easier than trying to rectify issues when the fixing compound is set hard.


Cutting natural stone paving slabs


Paving stones are best cut using a power saw or angle grinder, fitted with a diamond blade specifically rated for cutting stone. These can be hired locally and the hire depot will provide you with full instruction on how to use them safely.

Bear in mind that saw cutting of stone generates lots of harmful dust. Ask the hire depot about a water suppression kit to dampen down the dust and make sure you wear a suitable dust mask and safety eyewear.


One way to cut paving slabs is with a power saw/angle grinder:


1. Using a tape measure and chalk/pencil, measure the space where the slab will be slotted and mark the cutting line on both sides of the slab
2. Secure the paving slab to a workbench with the C-clamps. If done properly, the slabs should not move once it is secured.
3. Begin cutting through the paver with the power saw, using the marked line as a guide. Once you’ve cut about 1cm through one side, turn the slab over and repeat the process on the other side.
4. Continue until you have cut all the way through and then lay your newly cut slab into place.

In conclusion, although laying natural stone paving isn't rocket science, it’s hard labour and may take longer than expected. Arming yourself with the correct tools will make the job considerably easier and safer.

The key to the longevity of a successful project is the quality and attention to the substrate and surface the slabs are being fixed to. Extra time, effort, and expense at the substrate preparation stage is the best foundation for a project which will last a lifetime. A walk around your neighbourhood and taking a look at driveways is testimony to the paramount importance of base preparation.

To see the range of Natural Stone Paving at Stone Superstore click - Natural Stone Paving.

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