Rising Damp Treatment Calculator — DPC Injection Cream & Drill Spacing

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.