How to Fit Paving Slabs

At Creations Building & Landscaping, we install patios and paving, garden paths and outdoor spaces across Reigate and Surrey, and one thing we know for certain is this: good paving starts long before the first slab goes down. On our own projects, we focus on excavation, drainage, sub-base preparation, accurate laying and careful finishing, because that is what keeps paving looking neat and staying solid for years.

For a DIYer, the basic process is simple in principle. You mark out the area, dig to the right depth, create a firm sub-base, lay each slab on a full mortar bed, keep the fall running away from the house, and then joint everything neatly once the slabs have set.

Before you start: know what you are building

This guide is best for patio slabs and garden paving, not vehicle-bearing surfaces. If the area is going to take the weight of cars, the build-up usually needs to be stronger and designed differently, which is why we treat driveway installations as their own type of project. For patios, paths and seating areas, the method below is the right starting point.

What you need

You will usually need paving slabs, MOT Type 1 sub-base, sharp sand, cement, a shovel, rake, wheelbarrow, spirit level, tape measure, string line, rubber mallet, pointing tool, and a plate compactor for the base. Marshalls’ installation guidance also recommends a full wet mortar bed and regular level checks with string lines as you work.

Step 1: Mark out the area properly

Start by setting out the shape of the patio or path with string lines or spray marker. This is the stage where you make sure the layout works with the garden and leaves enough room for steps, doors and edges. At Creations, this planning stage matters just as much as the laying itself, because a paved area should feel like it belongs to the wider landscaping scheme, not like an afterthought.

Step 2: Set the levels and fall

Your paving must slope away from the house so rainwater does not sit on the surface or run back toward the walls. A common target is a fall of about 1:60 away from the property, and paving should usually be kept around 150mm below the damp proof course. That level can become more complicated around thresholds and door openings, but as a general DIY rule, never build the patio too high against the house.

Step 3: Dig out to the right depth

For a typical patio, Marshalls’ guide says to dig out roughly 150mm across the area so you have room for the sub-base and mortar bed. The dig needs to be consistent, and any soft or loose ground should be removed so you are not building on weak spots. This is one of the main reasons patio jobs fail: the surface looks good on day one, but the ground underneath was never prepared properly.

Step 4: Build a solid sub-base

Once the ground is dug out, add your Type 1 sub-base and compact it well. Marshalls’ concrete paving guidance says granular sub-base should be laid in layers no thicker than 75mm, with each layer compacted before the next is added. For a simple patio, Marshalls’ patio guide uses about 100mm of sub-base as a working rule. This is the layer that gives the paving strength, so do not rush it.

Step 5: Dry-lay a few slabs first

Before mixing mortar, place a few slabs loosely on the prepared area to check the layout, joint sizes and cuts. This helps you avoid awkward narrow pieces at visible edges and lets you confirm the pattern before things become permanent. It is a small step, but it saves a lot of frustration later. This is also the point where many homeowners decide whether they want a straightforward patio or a more detailed finish with edging, steps or features. On larger jobs, we often combine paving with brickwork to create clean edges, steps or raised areas.

Step 6: Mix the mortar bed

For a standard rigid patio build, Marshalls recommends a full wet workable mortar bed using 1 part cement to 3 or 4 parts sharp sand. The mortar bed is usually laid at around 30mm to 40mm before the slab is tamped down. The important point is that the slab should sit on a full bed, not on isolated dabs. Full support helps stop rocking, cracking and weak spots later on.

Step 7: Lay the first slab carefully

Start from a straight edge or a fixed reference point. Lower the first slab onto the mortar bed, then tap it down gently with a rubber mallet until it is level and sitting at the right height. Marshalls says the slab should ideally bed into the mortar by about 15mm. Check the level in both directions, then check the fall again before moving on. The first slab sets the tone for the whole job, so take your time here.

Step 8: Keep the joints even

Lay the next slabs in the same way, leaving a consistent joint between them. Marshalls’ patio guidance suggests joints of around 10mm to 15mm, and its concrete paving installation notes say butt-jointing is not recommended. Even spacing looks better, makes jointing easier and helps the whole patio feel more professional.

Step 9: Keep checking levels as you go

Do not wait until the end to see if the patio is level. Check every few slabs with a spirit level and use your string line to make sure the surface is still following the planned fall. Marshalls specifically recommends frequent checks on levels, gradients and joint widths during laying. It is much easier to correct a slab while the mortar is still fresh than after it has started to set.

Step 10: Cut slabs only where needed

Any cuts are best left until the main field of paving is down. Measure carefully and use the right blade and cutting equipment for the slab material. If you are laying natural stone or porcelain, neat cutting matters even more because poor cuts stand out immediately. On our own projects, material choice makes a big difference here, whether it is porcelain paving, natural stone or block paving.

Step 11: Leave the slabs to set

Once all the slabs are laid, leave them alone long enough for the bed to firm up. Marshalls says to leave the paving for at least 24 hours before walking on it, and longer in wet weather is sensible. Rushing this stage can knock slabs out of line before the base has had time to lock them in place.

Step 12: Joint the paving neatly

When the slabs have set, fill the joints with the correct jointing material for the type of paving and the manufacturer’s recommendations. Marshalls’ concrete paving guidance says that for most paving units with at least a 10mm joint, a damp mortar mix of 1 part cement to 4 parts building sand can be used, and any mortar on the slab surface should be cleaned off straight away. Neat jointing is what gives the patio its finished look and helps lock the surface together.

Common mistakes to avoid

The big DIY mistakes are nearly always the same: not digging deep enough, not compacting the base properly, laying slabs on dabs instead of a full bed, forgetting the fall, and building the paving too high against the house. All of those problems can lead to movement, rocking slabs, standing water or damp risk later on. They are also the exact reasons professional paving jobs spend so much time on groundwork and drainage.

Our honest advice

If you are fitting a small garden path or a simple patio and you are happy using levels, mixing mortar and taking your time, laying paving slabs can be a realistic DIY project. But if the job involves drainage issues, difficult levels, awkward thresholds, steps, retaining features or a larger patio that needs a really crisp finish, it is usually better to get a professional team involved. At Creations Building & Landscaping, we manage the full job from preparation to finishing touches, including paving, wider landscaping and related outdoor building work.

If you would rather have it done properly from the outset, you can see more of our paving work here or contact us for a free quote in Reigate, Redhill and the surrounding Surrey area.