How To Fill Gaps In Your Patio Or Paving Slabs

  • Learn how to fill in gaps in an inexpensive way.
  • Alternative joint-fillers for patios and paving slabs that you can use at home.

After all the time you spent on your paving, the last thing you need is unsightly gaps taking away from your hard work.

Why fill in the gaps

Filling in the gaps between your slabs and pavers might seem like a tedious task, but it can make your patio, path, or driveway look a lot cleaner and more professional.

When you’re laying the slabs for the first time, you’re more than likely just getting them all in position and focusing on ensuring that they are all an equal distance apart. This, in itself, already takes hours to do.

Paving is not a task made for the convenience of the homeowner. You have to have everything ready and on stand-by until a day where there’s no chance of rain and your concrete mix can dry for 24 to 48 hours.

What to consider

Before you get started with this Herculean task, you’ll need to check over your patio or paving slabs. Yes, even if you only just put them in a couple of days ago.

First, the bedding of the slabs. Is it level and sufficient? Does everything look even and well-prepared? Has your concrete dried correctly?

When it comes to bedding, you’ve either used flexible or rigid bedding. Flexible bedding means that there was no cement and that you put the slabs on top of aggregate. The only part of the bed of slabs that should be fixed in place is the perimeter of it.

Otherwise, you’ve used rigid bedding, where each slab has been placed atop a bed of cement.

Second, what is the function of the area that you’ve paved? Does it need to bear heavy loads – like a car – or just humans and animals?

Third, do you need liquid to be able to seep through the gaps of the paved area? This last one is particularly important because rainwater and other liquids will collect on your newly paved area if there’s nowhere for the liquids to go.

When you’ve answered these questions, you will know how much strength you need to give your paved area to ensure that it doesn’t get damaged easily. You’ll also know whether you need to be able to let liquid pass through the gap filler you’re about to use.

Patio gaps filled with wet mortar
Recently laid patio slabs with fresh wet mortar used to fill the gaps.

How to fill in the gaps

There are several methods that you can use to fill the gaps of your patio or paved area. Both dry and wet grouting are popular, but there are also other, less common, ways to fill these areas in.

Dry grouting

Dry grouting uses sand and cement to fill in the gaps of paving. The cement is moistened by natural moisture, rather than using water or pre-mixed wet cement. Building sand or the like is ideal for this type of joint filler, though there are a number of sands that can be used.

You’ll want a mixture that is three parts sand and one-part cement. No water should be used in this mixture at all. Once mixed, tip the mixture onto the paved area and brush it into the gaps that you’re looking to fill.

You should then flatten the mixture in the joints and repeat the process until the gaps are filled with a solid and firm amount of the sand and cement mixture.

Wet grouting

As a direct opposite of dry grouting, wet grouting uses the usual wet cement mixture plus sand to fill up the gaps in your paving. Any mixture that isn’t needed is simply washed from the paving.

Wet the unfilled joints before putting down any of the cement mixture. This mixture should be quite wet, almost soup-like, and is called either “mortar” or “grout”, which can be mixed on-site.

Spread the mixture over the slabs, using a brush to push it into the gaps between them and fill them in. Use a stiffer brush to remove the residue mixture once the grout has begun setting in the gaps of the slabs.

Gravel

A unique alternative to grout and other cement mixes, gravel can also be used as a patio or paving gap filler.

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This type of filler works better in patio areas that have wide gaps that need to be filled. It’s very cost effective and allows you to have better control over the customisation of your patio because gravel is widely available in a range of colours.

Gravel filled patio slabs
Lightly coloured gravel being used as a joint filler for this walkway.

Alternatively, you could use small pieces of slate. Both gravel and slate are known as loose fillers and don’t require any special cement mixes. Done properly, you shouldn’t experience any issues. Slate is a little larger than gravel, but it can look stunning when finished.

The next step up from gravel would be a filler like resin-bound gravel.

Resin

More recently used to fill entire driveways, there’s nothing stopping you from using resin-bound gravel to fill in smaller spaces like the gaps in your paving.

The resin-bound gravel (or resin-bound aggregate) that you pick up needs to be permeable. This will allow water or other liquids to pass through it. Otherwise, you’ll have an entire area of your property that liquid cannot penetrate.

Because gravel and similar aggregate is used in this mixture, you will again have a choice of colours that you can choose from to match the existing design of your patio or paved outdoor area.

Resin-bound gravel or aggregate are not the only kinds of resin filler, either. There are also various resin mortars that can be used to fill in gaps in patios and paved areas. The main two types are pre-mixed resin mortars and slurry-applied resin mortars.

Like any joint filler, there are advantages and disadvantages to using resin-based products to fill patio and paving gaps.

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