How far apart should DPC injection holes be drilled?

DPC injection holes should be drilled at 120mm centres (approximately every 4.7 inches) along the mortar course. Holes should be 10-12mm in diameter, drilled at a 30-degree downward angle into the mortar bed joint. This spacing ensures the silicone/siloxane cream spreads and overlaps between injection points to form a continuous damp proof barrier.

How deep should DPC injection holes be drilled?

Injection holes should penetrate to approximately two-thirds (⅔) of the wall thickness. For a standard 225mm solid brick wall, this means drilling to about 150mm deep. For a 100mm single-skin wall, drill to about 65mm. For a 275mm cavity wall, the inner and outer leaves are typically injected separately at appropriate depths.

How many DPC cream cartridges do I need per metre of wall?

For a standard 225mm solid brick wall, one 1-litre DPC cream cartridge treats approximately 1.2 metres of wall. Thinner 100mm walls use less cream (1 cartridge per 2.4m), while thicker 275mm cavity walls require more (1 cartridge per 1.0m). These rates are based on standard silane/siloxane DPC cream products such as Dryzone, Aida and Wykamol.

Why do walls need replastering after rising damp treatment?

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.

What standard covers rising damp treatment in the UK?

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.

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.

Wall Length

Average length per wall to be treated

Number of Walls

Number of walls requiring DPC injection

Wall Thickness

Determines drill depth and DPC cream volume per metre

Price Per DPC Cream Cartridge (optional)

Enter price per 1L cartridge for a cost estimate

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 cartridges = Total length ÷ Coverage per cartridge
Injection depth = Wall thickness × ⅔
Replaster area = Total length × 1.0m height
Salt neutraliser = Replaster area ÷ 3 (3 m² per litre)

DPC cream coverage rates

100mm single skin: 1 cartridge (1L) treats ~2.4m of wall
225mm solid brick: 1 cartridge (1L) treats ~1.2m of wall
275mm cavity wall: 1 cartridge (1L) treats ~1.0m of wall

Drilling specification

Holes are drilled at 120mm centres, 10–12mm diameter, angled downwards at approximately 30° into the mortar bed joint at DPC level (typically 150mm above external ground level). For cavity walls, the inner leaf is drilled from inside and the outer leaf from outside.

Replastering specification

Contaminated plaster is removed to 1m above the damp line. The masonry is treated with salt neutraliser, then replastered with renovating plaster (e.g. Dryzone Renovation Plaster or equivalent). Coverage is approximately 2 m² per 25kg bag at 20mm thickness. A minimum 3-coat system (salt inhibitor, base coat, 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

Last updated: February 2026

All calculations are estimates. Verify with your supplier.

Rising Damp Treatment Calculator — DPC Injection Cream & Drill Spacing

How We Calculate This

The formulas

DPC cream coverage rates

Drilling specification

Replastering specification

Standards

Frequently Asked Questions

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