Concrete is a strong and universal building material. It’s easy to use and cost-effective (in most situations). It’s only major disadvantage is its lack of flexibility: it won’t bend very far before fracturing.
It’s not uncommon for concrete surfaces to move gradually over time. The result can be a small crack, denoting the stress and movement. While such cracks can be superficial and unsightly, they can also allow water to penetrate the structure and cause a number of bigger problems. It’s best to repair any cracks before they become bigger problems.
Here’s our tips for simple concrete repairs.
1. Make sure it’s not a bigger issue
Concrete movements can be an indication of something more sinister. If in any doubt whatsoever, get it checked out by an expert before starting any repairs.
2. Widen and smooth the crack.
Applying mortar to a small crack can often result in the mortar cracking and falling out. It’s usually best to widen the gap to at least 20 – 30 mm to allow the mortar sufficient room to form and adhere to the sides. A simple hammer and cold chisel is usually enough, or you can hire one of our small demolition hammers. Any surface irregularities on the top surface should also be removed as these may hinder smoothing out the final coat.
3. Large cracks may require backfilling
Some cracks, especially if the are deep, may require backfilling. As well as providing a ‘backstop’ for the repair, the expandable foam products (such as the Gorilla range available from Mitre 10) help form a barrier against moisture and a bit of additional heat insulation.
4. Wet the crack
It may sound counter-intuitive but spraying the crack with water reduces the risk of the mortar cracking, by slowing the rate at which moisture is drawn from the mortar into the concrete.
5. Mix small lots
Mortar can set quickly, especially if over-worked. It’s usually best to mix up small amounts in quantities that you can use in 2-3 minutes.
6. Finish as required.
It’s always nice to try and obtain a finished appearance as close as possible to the neighbouring material. If the surface is slightly grainey, lightly apply a sponge to the concrete to remove some of the finer sand. If the surface is relatively smooth, work it gently with a metal trowel to bring the finer sand to the surface.
It’s surprising what 10kg of mortar and an hour or so of time can achieve. Good Luck!