- Phase 1 – Preparation
Inspection of rainwater goods to ensure they are fit for purpose. Clean, repair or install drains as required to carry away surface water. If the internal floors are below external ground level, form a trench along the external wall. The trench must be at least 150 mm below the proposed DPC level. Failing that, the DPC must be 150 mm above the external ground level and the internal walls tanked below the DPC. This prevents lateral migration of moisture and salts. Areas of affected plaster removed to a height of 300 mm above the highest level of the rising damp. Flooring timbers with signs of fungal decay and rot repair and replace. For cavity walls, it’s important to ensure no blockage or bridging within the cavity. Clean away any debris or blockage before installing a new DPC.
- Phase 2 – Drilling and Injection
Walls vary in thickness and type of construction. These factors determine the appropriate drilling and injection pattern. The DPC height should always be at least 150 mm above external ground level. The application for solid floors should be a as close to the floor level as possible.
Vertical DPCs connect horizontal DPCs where ground level changes and isolate untreated wall areas (adjoining walls and garden walls etc.). Solid walls drilled and injected from one side is possible under certain conditions. For cavity walls each leaf treated as a separate 115 mm thick wall. Stone and rubble in-fill walls, DPC made at the mortar course along appropriate level. If the stone is of a porous type, it may be possible to vary the drilling location (mortar/cement). Walls over 350 mm thick, holes required from both sides at a corresponding height.
- Phase 3 – Hole Size, depth and location
12 mm diameter horizontal holes in the mortar bed at centres no greater than 120 mm. Hole depth required for walls of various thickness:
Wall thickness 115 mm 230 mm 345 mm 460 mm (4.5”) (9”) (13.5”) (18”)
Depth of hole 100 mm 210 mm 320 mm 430 mm
- Phase 4 – Chemical Injection
Cream injection into pre-drilled holes. Each hole filled with cream to within one centimetre of the surface. For cavity walls from one side, the holes filled in each leaf.
Wall thickness: 115 mm 230 mm 345 mm 460 mm
Cream: 0.9 It 1.9 It 2.9 It 3.9 It per 10 m
- Phase 6 – Finishing works
Re-pointing holes on eternal walls using a matched mortar or plug with plastic caps. On internal walls, leave holes open and stop the plaster short of the DPC
- Phase 7 – Re-plastering
Removing and replacing salt contaminated plaster is important part of damp proofing works. Rising damp salts are hygroscopic (absorbs water) and can cause future staining. Before removing excess salts and commencing re-plastering, injected walls must be dry.
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