How to Repoint a Patio

Repointing a patio involves replacing the mortar between the slabs to ensure stability and prevent water from entering the joints. The cost of repointing your patio can vary depending on the size of the area, the type of material used, and whether you hire a professional or do it yourself. On average, repointing a patio can cost anywhere from £200 to £500, with the cost per square metre ranging from £10 to £30. However, if you decide to tackle the job yourself, you can save significantly on labour costs and only pay for the materials.

How to Repoint a Patio with a Dry Mix

Repointing a patio with a dry mix involves preparing a mortar mixture and filling in the gaps between your patio slabs. Here's how to do it:

1. Preparation: Start by clearing out any debris or old mortar from the joints between the slabs using a hammer and chisel. Make sure the joints are deep enough to hold the new mortar.

2. Mixing the Mortar: Mix dry sand and cement in a 4:1 ratio (four parts sand to one part cement). Add just enough water to create a firm but workable mix.

3. Filling the Joints: Use a pointing trowel to push the dry mortar mix into the joints, making sure the mixture is packed tightly. You may need to use a brush to sweep away excess mortar.

4. Smoothing the Joints: Once the mortar is in place, smooth the surface using a pointing tool or a piece of timber. Work carefully to ensure the joints are neat and consistent.

5. Cleaning the Slabs: After the mortar has set, use a soft brush to clean any excess mortar off the surface of the slabs.

How to Repoint Stone Paving

Repointing stone paving requires a slightly different approach due to the uneven and often porous nature of the stone. Here’s how to repoint stone paving:

Clean the Joints: As with regular repointing, start by removing any old mortar, dirt, or debris from the joints. For stone paving, you may need to use a wire brush to get into the crevices.

Prepare the Mortar: Use a mix of one part cement, three parts sand, and a small amount of lime for a more flexible mortar. This is especially important for natural stone paving, as the lime helps the mortar adhere better to the surface.

Apply the Mortar: Using a pointing trowel, push the mortar into the joints between the stones. It’s important to work in small sections, especially if the stones are irregularly shaped, to ensure the mortar fits well.

Smooth the Joints: Smooth the mortar with a pointing tool or the edge of a piece of timber. For stone paving, it’s especially important to ensure the joints are uniform and the mortar fills all gaps.

Cleaning: Once the mortar has dried, use a soft cloth to gently clean any remaining mortar from the stones. Be careful not to scratch the surface of the stones while cleaning.

Can I Use Sharp Sand for Pointing Slabs?

Sharp sand can be used for pointing slabs, but it’s best mixed with cement to form a strong bond. Some prefer to use a softer sand like building sand, but sharp sand is often more robust and can help the mortar set better. Ensure the sand is well-dried before mixing to avoid a weak pointing.

How Long Should Patio Pointing Last?

Properly applied patio pointing can last anywhere from 5 to 15 years, depending on the quality of the materials, weather conditions, and how well the patio is maintained. If the pointing starts to crack or deteriorate sooner, it might indicate issues with the mix, application, or drainage.

Why Is My Patio Pointing Cracking?

Cracking in patio pointing is often caused by a few factors:

• Shrinkage: Mortar shrinks as it dries, which can lead to cracking.

• Poor Mix: Using too much water or incorrect proportions of sand and cement can weaken the mortar.

• Movement: Ground movement or freeze-thaw cycles can stress the pointing, causing cracks.

• Lack of Expansion Joints: Without proper expansion joints, movement in the slabs can lead to cracking.

Step-by-Step Guide on How to Repoint a Patio

1. Preparation: Remove any old mortar and debris from the joints using a hammer and chisel. Ensure the joints are deep enough to hold the new mortar.

2. Mixing the Mortar: Mix sharp sand and cement in a 4:1 ratio (four parts sand to one part cement). Add water gradually until you achieve a firm, workable mix.

3. Filling the Joints: Use a pointing trowel to pack the mortar mixture into the joints. Make sure to press the mixture tightly to avoid air gaps.

4. Smoothing the Joints: Once the mortar is in place, smooth the surface using a pointing tool or piece of wood to create an even, neat finish.

5. Cleaning the Slabs: After the mortar has set, gently clean any excess mortar from the slabs using a soft brush or cloth.

6. Sealing (Optional): For added protection, apply a sealer to your patio to prevent dirt, moss, and weeds from regrowing in the joints.

Extra pointers for how t repoint a patio

1.Choosing the Right Mortar Mix

The quality of the mortar mix is crucial for ensuring the longevity of your repointing job. For standard patio pointing, a mix of 4 parts sand to 1 part cement works well. However, if you’re repointing natural stone or dealing with more significant movement or weather conditions, you might want to add a little lime to your mix. Lime helps to make the mortar more flexible and adaptable to changes in temperature and moisture.

2. Weather Conditions

It’s essential to check the weather before you start repointing. Avoid repointing during very wet or freezing conditions, as the mortar needs to set properly to achieve a strong bond. The ideal conditions for repointing are dry, mild days (not too hot or too cold) with little chance of rain. If it’s too hot, the mortar may dry out too quickly, causing it to crack. In cold weather, the mortar may take too long to set, which can also weaken the bond.

3. Removing Old Mortar Carefully

When removing old mortar, ensure that you don't damage the edges of your patio slabs. Use a hammer and chisel to remove the old mortar gently, ensuring you create a clean, deep joint without cracking the slabs. If you’re dealing with stubborn mortar, a power grinder can speed up the process, but be sure to use it carefully to avoid damaging the slabs.

4. Avoid Over-Wetting the Mortar

While it’s tempting to use plenty of water to make the mortar easier to work with, be careful not to over-wet it. Too much water can weaken the mix and cause it to set too quickly, leading to cracks and poor bonding. Always follow the manufacturer’s instructions for the correct water-to-mortar ratio.

5. Allowing Mortar to Set

After applying the mortar, make sure to allow it to set properly. This can take up to 24-48 hours, depending on the weather conditions. It's important not to walk on the repointed joints until they have fully set, as this could damage the work.

6. Sealing the Patio

Once the repointing is complete and the mortar has set, you might want to consider applying a sealer. A good patio sealant can protect the mortar from water damage and stains, as well as prevent moss and weeds from growing in the joints. Some sealants also help to make cleaning the patio easier in the future.

7. Addressing Common Issues

If you notice that your patio pointing is cracking soon after application, it could be a sign of either improper application or a mix that was too dry or too wet. Additionally, if your patio is sinking or shifting, it could put stress on the pointing, causing it to crack. In these cases, addressing the underlying issue of ground movement might be necessary.

8. Repointing Frequency

While repointing can last for many years, depending on weather and traffic, you may need to redo it every 5-10 years. Regularly maintaining the mortar and cleaning the patio will extend its life and keep the pointing looking neat.

By keeping these tips in mind, you can ensure that your repointing project is successful and that your patio remains in great condition for years to come.