Repointing Patio Joints: Mortar vs. Brush-In Compounds

Look at your patio. The slabs are likely fine, but the stuff in between them - the pointing - is cracked, missing, or full of weeds.

It ruins the look of the entire garden.

You know you need to fix it, but you are dreading it.

Traditionally, repointing meant mixing sand and cement, getting on your hands and knees with a tiny trowel, and spending three days trying not to stain the slabs.

But in the last decade, a new product has taken over the shelves: Brush-In Resin Compounds.

They promise a perfect finish in minutes, standing up, with a broom.

Is it too good to be true? Or is the "Old School" way still the best?

Here is the honest breakdown of the battle: Cement vs. Resin.

1. The Old School: Sand & Cement Mortar

This is how patios were laid for 100 years. It involves a 4:1 mix of Building Sand and Cement (often with a plasticiser to make it workable).

• The Pros:

• Cost: It is incredibly cheap. A bag of sand and cement costs pennies compared to tubs of resin.

• Strength: If done correctly, it sets rock hard. It provides structural support to the slab edges.

• Longevity: A good mortar joint can last 20+ years.

• The Cons:

• The Labour: It is back-breaking. You have to push the mix into the joint with a pointing iron, inch by inch.

• The Skill: You need to get the consistency perfect (damp earth, not wet slurry).

• The Risk: If you drop wet cement on a porous slab, it stains forever. You cannot wash it off.

• The Weather: If it rains while you are working, the job is ruined.

2. The New Wave: Brush-In Compounds (Polymeric Sand)

Sold under names like EasyJoint, Geo-Fix, or Sika FastFix.

This is a sand mixture coated in plant-based or synthetic oils/resins. It comes vacuum-packed in a tub. As soon as it touches air, it starts to harden.

• The Pros:

• Speed: It is roughly 10x faster than mortar. You can point a whole patio in an hour.

• Ease: No kneeling. You throw it on the floor and sweep it in with a broom.

• Cleanliness: You use water to wash it in. This cleans the patio as you work. No stains.

• Weather: You can apply it in the rain. In fact, it likes the rain.

• Permeability: It sets hard but remains porous. Rainwater drains through the joint rather than pooling on top.

• The Cons:

• Cost: It is expensive. One tub might cost £30–£50 and only cover 10–15 square metres.

• Strength: It is not as strong as cement. If you hit it with a high-pressure jet wash nozzle (pencil jet), you can blast it out.

• Weeds: While resistant, it is easier for strong weeds to punch through resin than concrete.

3. The Comparison: Which One Wins?

4. The Application Trick: Water is Key

If you choose the Brush-In method, most people make one mistake: They don't use enough water.

It feels wrong to soak a jointing compound, but for these products, it is essential.

1. Soak the Patio: Saturate the stones before you open the tub. This stops the oils from marking the stone.

2. Pour and Sweep: Tip the pile out. Sweep it into the joints.

3. The Hose: Have a hose running gently while you sweep. The water turns the sand into a slurry, helping it flow deep into the bottom of the crack.

4. The Strike: Once the joint is full, strike it off with the broom. The water compacts the sand down tight.

5. Decision Time: Which should you choose?

Choose Mortar if:

• You are on a very tight budget.

• You have huge, wide joints (over 20mm wide) where resin would be prohibitively expensive.

• The patio is loose/wobbly (mortar helps lock it in).

Choose Brush-In if:

• You value your time and your knees.

• You are worried about staining your expensive Indian Sandstone.

• You want the job done this afternoon, regardless of the weather forecast.

Conclusion

For the modern DIYer, Brush-In Compounds are the clear winner.

The extra cost of the tub is easily worth the two days of back pain you save. It transforms a nightmare job into a simple sweeping task.

• Clean the joints out first (min 20mm deep).

• Soak the patio.

• Sweep it in.