The correct depth to drill for DPC (Damp Proof Course) injection is to get within 10-20mm of the opposite face of the wall you're drilling into. You should use a 12mm drill bit and space the holes at 120mm intervals along the mortar joint.
Here's a breakdown for clarity:
- Target Depth: Drill to a depth that leaves 10-20mm of brick/stone/mortar intact on the opposite side of the wall. This avoids drilling completely through the wall.
- Drill Bit Size: Use a 12mm drill bit.
- Spacing: Drill holes at 120mm centres (120mm apart).
- Location: Always drill into the mortar joint, in a continuous line. Avoid drilling directly into the bricks or stone.
Why is depth important?
- Complete Saturation: Drilling to the correct depth allows the DPC injection cream to properly saturate the mortar joint, creating a continuous barrier against rising damp.
- Preventing Damage: Avoiding drilling all the way through prevents damage to the exterior wall and potential water ingress from the outside.
Steps for DPC Injection Drilling:
- Identify the Mortar Joint: Choose a continuous mortar joint near ground level.
- Measure and Mark: Mark drill points every 120mm along the chosen mortar joint.
- Drill: Using a 12mm drill bit, drill to the appropriate depth (wall thickness minus 10-20mm). Use a depth stop on your drill if necessary to avoid over-drilling.
- Inject DPC Cream: Inject the DPC cream into the boreholes using a low-pressure applicator (sprayer or cartridge gun) until the hole is filled.
- Seal (Optional): After the DPC cream has been injected and allowed to cure, you can optionally seal the holes with mortar.
Incorrect drilling depth can lead to an ineffective DPC and continued damp problems. Accuracy and consistency are key to a successful DPC injection.
