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Rising Damp Treatment Calculator — DPC Injection Cream & Drill Spacing
Calculate the number of drill holes, DPC cream cartridges, replastering area and salt neutraliser needed for chemical damp proof course injection to BS 6576.
Average length per wall to be treated
Number of walls requiring DPC injection
Enter price per cartridge (for the size selected above) for a cost estimate
Centre-to-centre spacing of injection holes (default 120mm)
Height of wall to replaster above damp line (default 1.0m)
Typical ~3 m²/L — coverage varies by product, so check your salt neutraliser/inhibitor datasheet and edit if needed
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How We Calculate This
This calculator determines the materials needed for a chemical DPC injection treatment based on your wall length, thickness and number of walls. It calculates drill holes, DPC cream, replastering quantities and salt neutraliser.
The formulas
- Drill holes = Total wall length ÷ 0.12m (120mm centres)
- DPC cream volume = Total length × ml per metre (datasheet rate for the wall thickness)
- Cartridges = Total cream volume ÷ cartridge size (380/600ml sausage or 310ml/1L cartridge)
- Injection depth = Wall thickness − 20mm (drill to within ~20mm of the far face)
- Replaster area = Total length × 1.0m height
- Salt neutraliser = Replaster area ÷ coverage (typical ~3 m² per litre — check your product)
DPC cream coverage rates
Derived from the Safeguard Europe Dryzone Damp-Proofing Cream datasheet (02/24): 600ml foil sausages per 10m of wall are 1½ (115mm), 3½ (230mm), 5 (345mm) and 7 (460mm). Corroborated by the datasheet’s 310ml-cartridge column and by Wykamol Ultracure (~5m per litre on a 230mm wall):
- 100mm single skin: ~90 ml/m (about 11m of wall per litre)
- 225mm solid brick: ~210 ml/m (about 4.8m of wall per litre)
- 275mm cavity wall: ~245 ml/m (about 4m of wall per litre)
Drilling specification
Holes are drilled at 120mm centres, 12mm diameter, horizontally into the mortar bed joint at DPC level (typically 150mm above external ground level) — DPC cream is thixotropic and stays in a horizontal hole, so no downward angle is needed. Drill to within ~20mm of the opposite face, easing drilling pressure for the final ~40mm. For cavity walls, the inner leaf is drilled from inside and the outer leaf from outside, each treated separately.
Replastering specification
Contaminated plaster is removed to at least 1m above the damp line (BS 6576). The masonry is treated with salt neutraliser, then replastered with a salt-resistant renovating plaster (e.g. Limelite Renovating Plaster or equivalent — gypsum plaster must not be used). Coverage is approximately 1.5 m² per 25kg bag at 20mm thickness (3 m² per bag at 10mm; minimum 20mm total over two coats). A multi-coat system — salt inhibitor, base coat and a non-gypsum finish coat — is standard.
Standards
Rising damp treatment should comply with BS 6576:2005 (Code of practice for diagnosis of rising damp) and be installed by PCA-registered contractors. Replastering should follow the renovating plaster manufacturer’s specification.
Frequently Asked Questions
DPC injection holes should be drilled at 120mm centres (never more) along a single mortar course, about 150mm above external ground level. Holes are 12mm in diameter and drilled horizontally directly into the mortar bed joint — not at a downward angle. Thixotropic DPC cream is designed for horizontal injection without run-out, so the holes follow the bed joint in one continuous line. The 120mm spacing lets the silane/siloxane cream diffuse and overlap between injection points to form a continuous damp-proof barrier.
Injection holes should be drilled to within about 20mm of the opposite face so the cream forms a continuous barrier — the Safeguard Europe Dryzone cream datasheet gives drill depths of 95mm for a 115mm wall, 210mm for a 230mm wall, 325mm for 345mm and 440mm for 460mm (i.e. wall thickness minus 20mm). For a standard 225mm solid brick wall that is about 205mm deep, and for a 100mm single-skin wall about 80mm. Drilling pressure is reduced for the final ~40mm of travel to avoid breaking through. For a cavity wall the inner and outer leaves are injected separately, each to within ~20mm of its far face.
Based on the Safeguard Europe Dryzone Damp-Proofing Cream datasheet (02/24), a 230mm wall uses three-and-a-half 600ml sausages per 10 metres — about 210ml per metre, or roughly 4.8 metres of wall per litre. The datasheet 310ml-cartridge column (6½ per 10 metres) confirms the same rate, and Wykamol Ultracure independently quotes around 5 metres per litre on a 230mm wall. Thinner 100mm walls use far less (about 90ml/m, ~11m per litre) and thicker 275mm cavity walls more (about 245ml/m, ~4m per litre). DPC cream is sold as 380ml or 600ml foil sausages and 310ml cartridges (not 1-litre cartridges), so a 230mm wall needs roughly one 600ml sausage every 2.9 metres.
Rising damp carries dissolved ground salts (chlorides and nitrates) up into the wall. These hygroscopic salts remain in the plaster even after the new DPC stops water rising. The contaminated plaster must be removed to at least 1 metre above the damp line and replaced with salt-resistant renovating plaster (to BS EN 998-1). A salt neutraliser or salt-inhibiting render is applied to the masonry before replastering.
BS 6576:2005 (Code of practice for diagnosis of rising damp in walls of buildings and installation of chemical damp-proof courses) is the key standard. It covers diagnosis, treatment specification and installation methods. The PCA (Property Care Association) also publishes codes of practice that members must follow. Treatment work should be carried out by a PCA-registered contractor for insurance-backed guarantee eligibility.
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Last updated: February 2026
Verified against UK standards · estimates only, confirm with your supplier.