How to Install Natural Stone Paving

Introduction

If you decide to go for natural stone in your outdoor living space, here is a guide to best explain how to install your natural paving slabs.

Before you start laying your slabs you will need to get the necessary tools to do the job. 

Firstly, you will need a measuring tape to measure out your designated patio area. You will need a wheelbarrow to transport your materials. For safety precautions we suggest that you wear protective gloves at all times while laying your patio. You will need a spirit level to determine how parallel or perpendicular your surface is. 

Tools and Materials You'll Need

Other tools you will need to use during this job include a pointing tool and a trowel. These tools will help shape mortar into the stone. You will need other tools to complete the job which include a rubber mallet, spade, rake, plate vibrator and a sponge.

Before you get all your tools in order you will need to get the materials necessary to lay your patio slabs. These materials are sandstone/limestone, sand, cement, water, spray paint and sub base material.

Step 1: Choosing and Marking Out Your Patio Area

Once you have all your tools and materials ready it’s time to get down to business and get cracking on laying your paving slabs, but how do you do this?

Firstly, you must decide where you want your pavement to be situated. There’s a few factors you should consider before choosing the best area to lay your sandstone paving slabs. Make sure the selected area is firm, level and well drained.  Mark out the area using spray paint.  

Step 2: Digging Out and Preparing the Sub-Base

Next grab your shovel and get down to a bit of digging. You must start by digging out your marked area. We advise that you dig 125mm at the minimum, plus the depth of your paving. You must remove all vegetation and top soil. Your finish surface depth should be 150mm or more.

Getting the Fall and Levels Right

Before any mortar goes down, your dug-out area needs a consistent fall, meaning a very slight downward slope away from the house or any structure. A fall of around 1 in 60 (roughly 16mm drop for every metre) is standard for a patio, and it's what stops surface water pooling against your walls or sitting on the paving itself after rain.

Set this up using timber pegs and string lines before you start digging to the final depth. Bang a peg into each corner of your marked-out area, use a spirit level resting across a straight length of timber to check level, then tap one end of each peg down slightly to introduce the fall, checking with the spirit level again after each adjustment. Running a string line tightly between the pegs gives you a constant reference line to dig and lay against, rather than relying on judging the slope by eye as you go.

If your patio sits against the house, the finished paving height should end up at least 150mm, or two full brick courses, below the damp proof course. Getting this wrong is one of the more expensive mistakes to fix after the fact, since it usually means lifting the patio to dig deeper rather than a simple top-up.

Sub-Base Depth and Compaction

The sub-base is what stops your patio sinking or cracking over time, and it's worth getting right even though it's the part nobody sees once the job is finished. A crushed stone hardcore, commonly known as MOT Type 1 and available from most builders' merchants, is the standard material for this layer.

Check your dug-out area is firm before adding any sub-base. Press your heel into the exposed ground; if it doesn't sink in, you're ready to proceed, and if it does, dig out and compact that soft spot further before continuing.

Add the sub-base in two layers rather than one, compacting each layer separately with a vibrating plate compactor (commonly available to hire) rather than just the first. Rake each layer level, run the compactor over it four to five times, check the depth against your string line and peg markings, top up any low spots, then compact a second time, ideally five to seven passes. Compacting in two stages rather than dumping the full depth in at once gives a noticeably more stable base, since a single deep layer tends to compact unevenly, with the top compressing while the bottom stays loose.

As a rule of thumb, you can't over-compact a sub-base, so more passes with the plate compactor is always the safer side to err on if you're unsure whether it's firm enough.

Step 3: Mixing Mortar and Laying Your Slabs

You cannot lay your slabs on soil or on top of grass. We strongly recommend that you use a wet mortar with a ratio of 5:1 wet mix of plastering sand and cement. Starting from a corner is the best option.  Trowel five large dabs of mortar at each corner and also in the middle of each slab as it will give you a full bed of mortar. It is absolutely essential that natural stone paving is laid on a full bed of mortar, this will prevent any slabs rocking or coming loose.

Your slabs will all vary in thickness, the thicker slabs should be used first, use your rubber mallet to tap your slab into the mortar. The use of the rubber mallet will ensure that your slabs won’t crack while putting them in. Once the first slab is laid you can put five more dabs of mortar onto the next slab. If you want to minimise the amount of pointing you will need to do, you could also lay a strip of mortar where the next joint will be.  

Throughout the laying process keep using a spirit level checking all the levels and falls. This is necessary because it will help create a patio with a slight fall in it, which will help make sure the area is drained properly. Certain slabs will need cutting. If you have decided to go for sandstone slabs the recommended tool to cut them with is a consaw.

What Is a Full Bed of Mortar?

A full bed of mortar means there are no gaps or voids between the back of the slab and the bedding layer beneath it, so the entire underside of the slab is in contact with the mortar. This is different from "dot and dab" methods sometimes used for other paving jobs, where mortar is only applied in a few points, and it's important for natural stone specifically because uneven support underneath is a common cause of slabs cracking under weight later on.

There are two common ways to achieve this. The first is to trowel five generous dabs of mortar (one at each corner and one in the centre), which spread out and merge into a solid bed as the slab is tapped down. The second is to spread the mortar across the full area in ridges using a trowel or float, which flattens out and fills in as the slab is bedded in. Both approaches work, provided the mortar mix is the right consistency: too wet and the slab will slide out of position as you work; too dry and it risks cracking under the tapping needed to bed it in.

Before laying a slab, it's worth removing any dust or loose debris from the back of it with a stiff brush, and some installers apply a bonding slurry or SBR (styrene-butadiene rubber) additive to the back of the slab first, which creates a stronger chemical bond between the slab and the mortar bed beneath it, on top of the mechanical grip from the mortar itself.

Blending Colour Across Your Patio

Natural stone is a genuinely natural product, which means no two slabs are identical, and colour can vary noticeably even within the same batch. This is expected and part of the appeal of natural stone over a uniform, manufactured product, but it needs a bit of planning during installation to look intentional rather than patchy.

If your project uses more than one pack or pallet of slabs, work from several packs at once rather than laying one pack fully before opening the next. Picking slabs from different packs as you go spreads any colour or tonal variation evenly across the finished patio, rather than creating a visible block of lighter or darker stone where one pack happened to sit apart from the rest.

Browse our sandstone paving slabs, limestone paving slabs, or granite paving slabs ranges to see the natural variation typical of each stone type before you order.

Jointing and Pointing Your Patio

Once your slabs are laid and the mortar bed beneath them has firmed up (usually the following day, once it's solid enough to stand on), the joints between slabs need to be filled, a process known as pointing. This isn't just cosmetic: unfilled joints let water track down into the mortar bed and sub-base beneath, which over time can undermine the whole installation.

A few dimensions matter here regardless of which jointing product you use: joint width should be a minimum of 6mm, and joint depth a minimum of 24mm, to give the jointing material enough of a key to bond properly rather than sitting loose on the surface. Clear any debris from the joints with a stiff brush before applying any jointing compound.

Both traditional sand-and-cement pointing and modern resin-based jointing compounds are used for natural stone. Resin-based compounds tend to be more flexible and less prone to cracking than a straight sand-cement mix, and most can be applied across a wider temperature range, generally anywhere from just above freezing up to the mid-20s Celsius, and even in light rain, though it's always worth checking the specific product's application guidance. Whichever you use, work it into the joints with a brush or pointing tool, compact it down firmly so there are no air gaps, then sweep away any excess on a diagonal across the joints rather than along them, since sweeping along a joint tends to pull the material back out rather than clearing the surface.

Aftercare and Sealing Your Natural Stone Patio

In the aftercare of your natural stone slabs we suggest that you seal your sandstone/limestone every 2-3 years. In our view the best sealer on the market is Stontex Platinum Stone Sealer, this product is available to purchase on our website. Sandstone can sometimes be prone to flaking on the surface. As it is a natural product this cannot be prevented, the only remedy is to brush away any pieces of stone that flake off.

Beyond periodic sealing, a natural stone patio benefits from a light sweep or hose-down every few weeks to stop dirt, algae, or moss establishing themselves, particularly in shaded or damp corners of a garden. A stiff outdoor brush and clean water is usually enough; avoid pressure washing directly into the joints too often, as repeated high-pressure washing can gradually erode jointing material over the years.

For a real example of a finished natural stone project from start to end result, see our feature on how a 67-year-old built a dream garden retreat with sandstone paving.

Common Mistakes to Avoid

Like everything there is a right way and a wrong way of doing things and this is no different. Here’s a few things to be careful of when installing your slabs. The simplest bit of advice is to make a plan before you start the construction process and you should also consult a paving expert before undergoing your project. 

Make sure that your joints are running both ways, both transversely and longitudinally. It is vitally important that you get the ratio right when mixing your mortar. If your mortar is too wet water will leak out and if it’s too dry it will eventually crumble. Another big mistake people can sometimes make is they under buy the amount they need. 

We advise that you slightly over-buy as tiles/slabs come in batches with every tile/slab in the batch having a similarity if you order a little amount at a time you could possibly end up with mismatches.

All the products you would need to complete your patio and improve your outdoor lifestyle are available to purchase on our website, such as limestone and sandstone slabs plus all the other paving accessories. If you follow these instructions, we have no doubt you will/ do a great job laying your natural paving slabs.  

Why Tile Merchant?

We offer extremely competitive pricing on our entire range of tiles and likewise. We stock a huge range of wall and floor tiles and our prices are competitive for retail and trade. Our stock is widely available in our tile stores in Ireland, which are open 7 days a week.
Alternatively, if you’d prefer to shop our tiles online, we can supply you with samples delivered for free.