How to use paving jointing compound for the perfect paving finish

If you’ve never used paving jointing compound before, fear not – it’s a lot easier than you might think! We’re here to help you quickly learn how to use paving jointing compound, as well as what you’ll need and why it’s important.

What is paving joint compound?

Paving jointing compound is a type of hard-wearing patio grouting used to fill the gaps between paving, flagstones, slabs and cobblestone. It’s designed to set quickly, even in wet weather, and once set, it helps prevent weeds and other unsightly growth from popping up between your paving. Whether you’re working with old pre-existing paving or laying completely new paving, jointing compound helps give it that smooth, perfectly level finish. 

Paving joint compound and paving grout come in a variety of different types,  including epoxy resins, cement-based slurry grouts and traditional cement mortar. But the most common and easy to use type of patio joint compound is the ready-mixed sweep or brush-in compounds, otherwise known as polymeric compounds. 

These come in ready-to-use bags and buckets for easy application, and they are safe to use on a wide range of different stone types, making them an ideal choice if this is your first time using a paving jointing compound. 

Where can I use paving joint compound?

Paving jointing compound, particularly the brush-in kind, is incredibly versatile, environmentally friendly and can be used for a wide range of different floor-laying projects and repairs, including:

• Outdoor patios
• Pathways
• Driveways
• Indoor stone floors
   

It is always best to check that you are using the right type of jointing compound that is suitable for use with your chosen type of stone as well as the function of the area you’re paving. 

Make sure you check this before you choose and apply your compound, as using the wrong type can lead to unsightly staining on your beautiful new paving stones. The pre-mixed sweep-in jointing compounds are usually safe to use on the vast majority of stone types, but it’s always better to be safe than sorry!

It is also important to make sure you choose the right colour of jointing compound to match or complement your paving stones. Compounds come in a range of classic colours from pale natural stone to various shades of brown, grey and even black. 

So, now that we’ve covered what jointing compound is and what it’s used for, let’s get into how to use it. 

Removing old mortar or compound

This section is only relevant if you are trying to re-joint or repair existing paving. If you’ve just laid brand new paving, then skip to the next section.

If you’re re-jointing an old patio, the chances are high that it was originally grouted with traditional cement-based mortar that is cracking and failing. This will need to be removed completely before you apply your new jointing compound. 

TIP: If you’ve got loose or moving paving slabs, you will need to re-bed and fix these down before you apply your new jointing. If you re-joint paving that has loose slabs, all your hard work and effort will be wasted as your new jointing is likely to crack again. 

What you will need:

You might not need all of the below items. The tools you need will depend on the type of existing mortar you are removing and how stubborn it is to remove.

• A patio knife or other ‘hooked’ tool (ideal for removing weak, crumbly mortar)
• A hammer and bolster or chisel (for chipping away stubborn mortar)
• A yard brush (for sweeping out old mortar)
• A hose or pressure washer (for clearing out old mortar)

TIP: If you’ve got especially stubborn, strong mortar or patio joint compound that the above tools cannot remove, you may need a mechanical saw or angle grinder. In this case, you may need to seek help from a professional patio layer.

Step 1: Cut out the old mortar

Using your patio hook or hammer and chisel, start to rake along the joints or chip away at the old mortar until it crumbles and comes away from the gaps. You’ll need to cut out a channel at least 15 to 30 mm deep, which is the depth most patio jointing compounds require to be most effective (check the instructions on your new jointing compound to get the exact depth you need). Take care not to damage the edges of your flag stones as you cut out your old mortar.

Step 2: Clean the joints

Now that your mortar is all loosened off, you’ll need to clean away all the fragments and any residue that remains. This is an important step as excessive dust and mortar fragments will prevent your new compound from lasting. If you mainly just have dust remaining, your brush will usually be enough to sweep away any lingering residue and larger fragments. But, if your old mortar was particularly stubborn, you may also need to use your hose to flush out any remaining mortar fragments from the joints. 

All done! Now you’re ready to use your jointing compound.