If a damp-proofing company has told you that you need a new damp proof course, tanking or a full replaster, you may well be right to pause before signing. Sometimes damp proofing is the answer, but much of the damp in older houses, especially solid-walled stone and brick terraces, isn’t rising damp at all, and treating it as if it were can cost thousands without fixing the problem. This guide explains what a typical quote contains, when it makes sense, the red flags to look for and what to ask.
What does a typical damp-proofing quote include?
Most quotes from damp-proofing contractors are built from the same few elements:
- Chemical DPC injection: drilling a line of holes near the base of the wall and injecting a water-repellent cream to form a new damp proof course (DPC), a barrier against moisture rising from the ground. See damp proof courses: when they’re the answer for background.
- Hacking off and replastering: removing the lower plaster, often to about a metre high, and replastering with a salt-retardant or waterproof render-and-plaster system to hold back salts left behind in the wall.
- Tanking or membranes: applying a waterproof coating or fixing a studded plastic membrane to the wall, common in cellars and on walls below ground level.
- Timber treatment: treating skirtings, floor joists or other timbers for rot or woodworm.
- A long guarantee, often 20 or 30 years.
None of these is a bad product in itself. The question is whether it addresses what is actually making your wall damp.
When is damp proofing the right answer?
Damp-proofing work can be appropriate when an investigation shows:
- the existing DPC has genuinely failed or is absent, and moisture is rising from the ground in the pattern you’d expect;
- there’s no simpler cause, such as high external ground, a bridged DPC, a leaking drain, a defective gutter or condensation, that explains it instead;
- the wall is a type that injection can reliably treat; or
- in a cellar or basement, where walls are below ground and some form of waterproofing is needed if the space is to be used.
Why damp proofing is often the wrong answer
The Society for the Protection of Ancient Buildings (SPAB) notes that true rising damp is rarer than commonly perceived and is regularly misdiagnosed. Historic England’s guidance on damp in older buildings explains why it matters. Traditional solid walls were built from permeable materials such as stone, brick and lime mortar, which absorb moisture and then release it when conditions dry. Problems often start when that balance is upset.
The more common causes of damp low down on a wall are:
- External ground or paths raised above the original DPC level, or soil banked against the wall;
- Render or pointing carried over the DPC, creating a bridge;
- Leaking gutters, downpipes or drains soaking the base of the wall;
- Rain penetration through weathered pointing, porous stone or cracked render, very common on exposed gritstone and sandstone houses across the Pennines;
- Condensation on cold walls, especially behind furniture and in corners;
- Impermeable modern finishes such as cement render, gypsum plaster and plastic paints trapping moisture in walls designed to breathe;
- Plumbing leaks, especially in kitchens and bathrooms.
Injecting a new DPC won’t fix any of these. Replastering with a waterproof system can hide the symptoms for a while, but in some solid walls it simply pushes moisture somewhere else. Our guide to what rising damp is goes into this in more detail.
Red flags in a damp-proofing quote
Look out for:
- Diagnosis by electrical moisture meter alone. These meters are designed for timber. On masonry and plaster they give comparative readings at best, and salts in the plaster can produce high readings on a wall that’s actually fairly dry. The Property Care Association’s own guidance on moisture meters and the joint RICS, Historic England and PCA position statement both warn against relying on misleading data.
- No mention of the outside of the building. If the report doesn’t mention ground levels, gutters, downpipes, pointing, render or drains, the investigation wasn’t complete.
- An injected DPC proposed for a thick stone or rubble-filled wall with the same confidence as for a standard brick wall. Irregular stone walls with rubble cores are much harder to treat reliably by injection.
- Rising damp diagnosed on an upstairs wall, or well above the height ground moisture could plausibly reach.
- Tanking proposed for an above-ground wall without explaining why breathable solutions won’t work.
- Timber treatment recommended “as a precaution” with no evidence of active rot or insect attack.
- Pressure to decide quickly, such as “this price is only valid today”.
- The free survey is carried out by the company that sells the treatment. That’s not necessarily dishonest, but it isn’t independent.
Questions to ask before you agree to damp-proofing work
- What exactly is causing the damp, and how did you establish that?
- What tests did you do besides a moisture meter? Were samples taken to separate real moisture from salts?
- Have you checked the outside: ground levels, the existing DPC, gutters, downpipes, pointing and drains?
- Why won’t a simpler repair work first?
- Is this treatment suitable for this wall’s construction and age?
- What plaster will you use, and will the wall still be able to breathe?
- What does the guarantee cover and exclude, and is it insurance-backed?
A competent contractor should be able to answer all of these clearly.
What does a 30-year damp-proofing guarantee actually cover?
Long guarantees sound reassuring, but read the terms:
- They usually cover the specific treatment installed, in the specific areas treated, not damp in general.
- They typically exclude damp from other causes, such as condensation, rain penetration, leaks or bridging. If the original diagnosis was wrong, the guarantee may not help.
- They often depend on you maintaining the property, for example keeping gutters clear and ground levels down, and reporting problems promptly.
- A guarantee is only as good as the company behind it. Some guarantees are insurance-backed, which can protect you if the contractor stops trading, but the insurance cover may not run for the full guarantee period. Check.
A guarantee is no substitute for a correct diagnosis.
What an independent damp survey adds
An independent damp survey is carried out by a surveyor who doesn’t sell damp-proofing, so there’s no reason to recommend one fix over another. It typically:
- inspects outside and inside, looking for all the possible moisture sources;
- uses moisture readings carefully and comparatively, with sampling where needed to separate true moisture from salts;
- considers the age and construction of the walls;
- explains the cause in plain English, and recommends the simplest effective fix, which may be clearing a gutter, lowering a path or replacing cement render with lime.
Where damp proofing really is needed, the survey says so, and you can get quotes with confidence. Where it isn’t, you’ve avoided paying for the wrong work. Read more about why independence matters and what happens in a damp survey.
Damp proofing in Huddersfield, Leeds, Manchester and across the North
If you’re searching for damp proofing in Huddersfield, Halifax, Bradford, Leeds, Sheffield, Manchester or Oldham, you’re probably living in or buying exactly the kind of house where misdiagnosis is common: a solid-walled Victorian terrace, a stone cottage, or a back-to-back, often exposed to heavy Pennine rain. These buildings frequently have more than one source of damp, and the fix is often maintenance rather than injection.
Get a second opinion before you pay
We carry out independent damp and timber surveys across West, North and South Yorkshire, Greater Manchester and surrounding areas. Our surveyor is a PCA Qualified Technician in damp and timber, and we sell no treatments or repairs, so our only interest is getting the diagnosis right. If you already have a quote, send it with your enquiry so the survey can address what’s been proposed. Try the damp checker for a quick first view, or read how to treat damp walls. Then get in touch for a fixed fee quoted for the property.
Sources and further reading
- What is rising damp? — Society for the Protection of Ancient Buildings
- Damp in historic buildings — Historic England
- Investigation of moisture and its effects on traditional buildings: joint position statement — RICS, Historic England and PCA
- Guidance document: the use of moisture meters to diagnose dampness in buildings — Property Care Association
- Damp proofing advice for homeowners — Property Care Association