Summary: Learn how to inject damp proof course, detecting the cause of damp and using damp proof course injection to prevent future damp.
If you find that damp is a continued problem even with a damp-proof course you may want to check that there isn’t something causing the damp on the outside wall such as a flowerbed or old building material dumped against the wall. If this is not the case then you may need to replace the damp-proof course (DPC).
Damp proof course injection
One possible way of doing this is to inject a waterproof silicone-based compound into the wall, which forms an impervious layer.
- The injected damp-proof course can either be inserted from just the outside wall or from both sides. You must check the manufacturer’s instructions on how best to use their product.
- Start by using a drill with an 18mm – 25mm diameter masonry bit. Drill holes in the mortar of the outside wall 150mm above ground level and 115mm apart from each other. Drill to an approximate depth of 190mm. If you do decide to drill from both sides, then the holes only need to be 75mm deep.
- When drilling, either drill squarely into the mortar, or at a slight downward angle.
- When all the holes have been drilled sufficiently, you can now fill them with the silicone-based damp proof compound. Using a sealant dispenser loaded with a cartridge of the compound, insert the nozzle into the holes and carefully inject until 10mm of the hole remains unfilled.
- Once the compound has been allowed to settle fill the remaining 10mm gap with mortar.