How to Price Chemical DPC Injection: Labour, Materials and Margin Guide

Summary

Chemical DPC injection is frequently subcontracted as a discrete, priced-by-the-metre technical operation — either by a damp specialist pricing the injection element of a bigger job separately from replastering, or by a general builder bringing in a specialist for just the drilling and injection while handling the make-good themselves. Priced this way, injection is closer to a piecework trade than a diagnostic service: known wall thickness, known hole spacing, known cream volume, known drilling and injection time per metre. This guide covers that build-up in detail — equipment, technique, BS 6576 hole spacing and depth specification, cream volume by wall type, and how a specialist prices day output rather than a whole-job total.

This is deliberately narrower than damp proof course pricing guide, which covers the full job including diagnosis, the case for and against genuine rising damp, replastering specification, drying-time management, and bridging removal. Do not quote injection in isolation without the diagnostic step covered there — the single most common cause of an ineffective (and reputation-damaging) DPC injection job is injecting a wall where the actual problem is penetrating damp, condensation, or a bridged existing DPC, none of which chemical injection fixes. This guide assumes diagnosis has already established that chemical injection is the correct remedy, and focuses on pricing the injection operation itself accurately.

Key Facts

• Drilling — 10-12mm diameter holes drilled into the mortar bed at DPC level, angled slightly downward into the wall on some specifications, spaced at 100-120mm centres along the wall — confirm exact spacing and angle against the specific product's technical data sheet, since methods vary between cream/gel systems
• Hole depth — typically drilled to within 25-50mm of the far face of the wall, deep enough to form a continuous barrier without fully penetrating through
• Injection volume — single-skin wall (approx. 230mm) — around 1.0 litre of cream per linear metre
• Injection volume — cavity wall (approx. 340mm, both leaves treated) — around 1.5-2.0 litres per linear metre
• Drilling time per metre — 8-12 holes at 100-120mm centres takes roughly 15-25 minutes to drill per linear metre with a standard SDS/rotary drill and masonry bit
• Injection time per metre — 4-8 minutes per metre using a cartridge gun (manual or battery) for cream systems; gravity-feed fluid systems take considerably longer per metre and are less common on domestic retrofit work now that cream systems dominate
• Combined drill + inject labour per metre — roughly 20-35 minutes total per linear metre for a competent single operative on a straightforward, accessible wall
• Hole filling/making good the drill holes — mortar plug or matching pointing mix, small additional time per metre, usually folded into the injection labour rate rather than costed separately
• Equipment — SDS rotary drill with masonry bits (consumable — bits wear and need regular replacement, cost this into the day rate), cartridge/injection gun (manual guns are cheaper, battery-powered guns speed up high-volume days), dust extraction/PPE for drilling into old mortar
• Cream/fluid product cost — £6-£12 per linear metre of material for a mid-range proprietary silane/siloxane cream system, varying by brand and wall thickness
• Access obstructions — skirting boards, internal fitted furniture, external planting/paving hard against the wall all slow drilling access and should be priced as a site-specific addition, not absorbed into the per-metre rate
• Wall construction variability — rubble-filled or irregular older walls (common pre-1900) can be harder to drill consistently and may need adjusted hole spacing or supplementary treatment at problem sections; flag this as a day-rate risk on older properties rather than a fixed per-metre price
• BS 6576:2005+A1:2012 — the governing code of practice for diagnosis of rising damp and installation of chemical DPCs; injection specification (hole spacing, depth, volume) should follow the product manufacturer's data sheet, which is written to be compliant with BS 6576 principles
• Insurance-backed guarantee registration — £35-£90 to register per job with the product manufacturer's guarantee scheme; a non-negotiable inclusion on any commercial-facing quote, since lenders and conveyancing solicitors expect to see it at point of sale
• VAT — 20% standard rate

Quick Reference Table

Detailed Guidance

Confirm diagnosis is already done — do not skip this

This article prices the injection operation on the assumption that a proper diagnostic process — moisture profiling, checking for bridging, ruling out penetrating damp and condensation — has already confirmed chemical DPC injection is the correct remedy. That diagnostic process, the evidence for genuine rising damp versus the more common alternatives, and the bridging checks that can make injection entirely unnecessary, are covered fully in damp proof course pricing guide and damp proofing pricing guide. Quoting or carrying out injection without that step is how the damp-proofing trade earned its poor reputation, and it's a guarantee claim waiting to happen when the "rising damp" turns out to be a leaking gutter.

Drilling technique and pattern

The injection barrier depends on a continuous, evenly spaced line of saturated mortar, so the drilling pattern matters more than the drilling itself:

1. Locate the mortar bed at DPC level (or, where no effective DPC exists, at a consistent height roughly 150mm above external ground level, per typical product guidance) — drilling into brick rather than mortar reduces the cream's ability to spread through the wall.
2. Mark hole centres at the spacing specified by the product data sheet, typically 100-120mm — consistent spacing matters more than exact spacing, since gaps in the barrier are where future capillary rise finds a path.
3. Drill to the specified depth, angled per the product's instructions (some systems specify a slight downward angle to help the cream settle and spread; others specify horizontal) —.
4. Clear dust from the holes before injecting — dust in the hole reduces the cream's contact with the surrounding mortar and can create weak points in the barrier.
5. On cavity walls, both leaves need treatment, roughly doubling the drilling and injection work per linear metre of external wall length — price this as additional time, not folded into the single-skin per-metre rate.

Injection technique and volume control

Cream-based systems (the dominant product type on UK domestic retrofit work) are injected with a cartridge gun, either manual (cheaper, slower on high-volume days) or battery-powered (faster, worth the investment above a certain day-rate volume). Underfilling holes is the most common technique failure — the cream needs to fully saturate the mortar bed around each hole, and rushing the injection to hit a day-rate target undermines the barrier's continuity. Overfilling wastes material without improving performance. Follow the manufacturer's stated volume per metre for the wall thickness being treated, and don't let time pressure on a day-rate job erode the fill quality.

Pricing as a day-rate specialist operation

Where injection is being priced as a standalone specialist package (rather than folded into a full remediation quote), build the price from time and materials rather than a flat headline figure:

• Labour — a competent single operative can typically drill and inject 15-25 linear metres in a working day on straightforward, unobstructed walls, less on obstructed or irregular older walls
• Materials — cream/fluid cost per metre plus a consumables allowance for drill bits (masonry bits wear quickly in old, hard mortar and are a real cost, not negligible)
• Equipment amortisation — SDS drill and injection gun capital cost spread across expected annual metreage
• Insurance-backed guarantee registration — £35-£90 per job, always itemised, never absorbed silently
• Margin — 20-30% is typical for a specialist subcontract package; injection-only work carries lower risk than full diagnosis-and-remediation contracts (the diagnostic liability sits with whoever specified the treatment), which can justify pricing slightly tighter than a full-service damp company

What to explicitly exclude from an injection-only quote

Because this is often priced as a discrete package within a bigger job, be explicit in writing about what's NOT included:

• Diagnosis (unless separately commissioned — see damp proof course pricing guide for survey pricing)
• Replastering to salt-resistant specification (a separate, larger cost — see the replastering detail in the companion article)
• Bridging removal (raised paths, failed render laps, floor screeds) if identified during survey
• Redecoration after replastering
• Any structural or masonry repair unrelated to the DPC itself

A quote that says "DPC injection — £680" without this exclusion list invites a dispute when the customer expects replastering and redecoration included.

Access obstructions — price them, don't absorb them

Fitted kitchen units, built-in wardrobes, or external hard landscaping (patios, raised beds) hard against the treated wall all slow drilling access significantly, sometimes requiring furniture removal or drilling from an awkward angle. Survey for these before quoting a per-metre rate, and price obstructed sections as a day-rate supplement rather than trying to average the extra time into a single blended per-metre figure across the whole job.

Frequently Asked Questions

What's the difference between this and a full DPC pricing guide?

This guide prices the drilling and injection operation itself — technique, equipment, hole spacing, volume, day-rate output — as a discrete specialist skill. damp proof course pricing guide covers the whole job end to end: diagnosing whether rising damp is genuinely present (frequently it isn't), replastering specification, drying-time management, and checking for DPC bridging that might make injection unnecessary altogether. Read that article first for any job where diagnosis hasn't already been established; use this one to price the injection element accurately once it has.

How many holes per metre does a chemical DPC injection need?

Typically 8-12 holes at 100-120mm centres per linear metre of wall, drilled into the mortar bed at DPC level. Exact spacing varies by product — always follow the specific manufacturer's technical data sheet rather than a generic spacing figure, since cream viscosity and spread characteristics differ between systems.

Can I quote DPC injection without seeing the wall thickness first?

Not accurately. Cavity walls need both leaves treated (roughly double the single-skin injection volume and time), and wall thickness directly drives cream volume per metre. A generic per-metre price without confirming construction type risks under-pricing cavity walls significantly. Confirm wall type — solid single-skin, cavity, or rubble-filled older construction — before finalising a per-metre rate.

Why is injection-only pricing so much lower than the full DPC job price?

Because replastering — hacking off contaminated plaster, applying a salt-resistant renovation system, and finishing — typically costs more than the injection itself. Injection alone (drilling and chemical treatment) is a fast, mechanical, per-metre operation; replastering is a slower, skilled, per-square-metre operation. Quoting the two separately, as this guide does for the injection element, is standard practice when a specialist is being brought in for just the technical injection step.

Does the drilling pattern need to be perfectly continuous with no gaps?

As close to continuous as the wall construction allows. Gaps in the treated mortar bed — from missed holes, obstructions that prevent drilling at the correct spacing, or inconsistent depth — create weak points where capillary rise can still occur, undermining the whole barrier even if 95% of the wall length is correctly treated. Where an obstruction genuinely prevents drilling at the standard spacing, flag it and agree a workaround (adjacent hole spacing tightened, or treatment from the opposite face) rather than leaving an untreated gap.

Regulations & Standards

• BS 6576:2005+A1:2012 — code of practice for diagnosis of rising damp in walls of buildings and installation of chemical damp-proof courses

• Building Regulations Approved Document C — site preparation and resistance to contaminants and moisture (England & Wales)

• PCA Code of Practice for Remedial Treatment of Rising Damp — industry-standard specification referenced by most proprietary injection product data sheets

• Construction Products Regulations 2013 (SI 2013/1387) — implements the EU Construction Products Regulation 305/2011; applies to DPC cream/fluid products

• Consumer Rights Act 2015 — affects warranty terms and service standards on installer guarantees

• Property Care Association — Damp guidance — trade body diagnostic and installation standards

• GOV.UK — Approved Document C — Building Regulations

• BSI — BS 6576:2005+A1:2012 — chemical DPC code of practice

• BRE — Understanding Dampness in Buildings — research-based diagnosis framework

• damp proof course pricing guide — the full DPC job: diagnosis, replastering, drying time, and bridging checks — read this first if diagnosis isn't already established

• damp proofing pricing guide — broader damp treatment category including tanking and cavity drain membrane alternatives

• rising damp — rising vs penetrating damp diagnosis detail

• dpc replacement — DPC replacement methods including physical and electro-osmotic alternatives to chemical injection