Damp
Is it rising damp or condensation?
Condensation, penetrating damp and rising damp are different mechanisms, so they are not one repair. A moisture meter on a home survey is not proof of rising damp. GOV.UK guidance on damp and mould is written for rented-housing providers. It treats mould as a health risk, not as a buyer discount.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless a source says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the difference between condensation, penetrating damp and rising damp?
These are three mechanisms that can look similar in a photograph. Condensation is moisture from indoor air landing on a cold surface. It is often a heating and ventilation problem, and it is a common explanation for mould on external corners and behind wardrobes. Penetrating damp is rain getting in from above or from the side: a gutter, a downpipe, a flashing, cracked render, or eroded pointing. Rising damp is moisture from the ground moving up a wall where the damp-proof course is missing, bridged or defeated. In a purchase in England or Wales, the survey should say which of these it thinks is likely, and where it is not sure.
| Mechanism | Where the water comes from | What a first repair is aimed at |
|---|---|---|
| Condensation | Indoor air on a cold surface | Heating, ventilation and the cold surface, not an injected course |
| Penetrating damp | Rain from above or the side | The gutter, flashing, pointing or other leak path |
| Rising damp | The ground | The real path from the ground, and only then any treatment of the wall |
Why is a moisture meter not proof of rising damp?
Surveyors use a moisture meter as a screening tool. A high reading tells them that the surface is wetter than they would expect. It does not, on its own, show that water is rising from the ground. Salts in an old wall, foil-backed paper and a cold surface can all confuse a reading. The Property Care Association groups damp with other structural moisture problems for homeowners, and it still has to be diagnosed, not assumed from one number.
Read the pattern. Low-level staining with a tide mark, salts, and high outside ground is a different picture from mould on a cold north wall, and different again from a brown stain under a valley or a leaking downpipe. A RICS home survey records what was visible. The Level 3 description is a condition report of what the surveyor could see and judge. It is not a laboratory test of the wall. If the paragraph says further investigation, that is the limit of the inspection, not a hint to accept the first injection quote.
How should a buyer read government damp and mould guidance?
GOV.UK publishes damp and mould guidance for rented-housing providers. It explains the health risks of damp and mould for people living in those homes. It is not the RICS home survey standard, and it does not set a price reduction for a buyer in England or Wales. Do not turn it into a percentage off the purchase price. There is no honest figure of that kind in the guidance.
Use it for what it is. Mould is not only a decorating stain, especially in a room someone will sleep in. The repair is still the mechanism the survey describes. If you will let the home, the rented-housing duties sit with that guidance and with your solicitor’s advice. If you will live in it, the same health point is a reason to find the cause before you exchange, not a reason to buy a chemical treatment that ignores the cause.
What should you ask before you accept a damp-proofing quote?
Ask the surveyor to separate observation from cause. Then ask any specialist the same questions. A quote that says damp proofing, without naming condensation, penetrating damp or rising damp, is not a quote for the defect in the report.
- Where is it, and what was seen: mould, salts, a tide mark, a stain from above, or only a meter reading?
- Which mechanism is most likely, and what evidence would show that is wrong?
- Are the gutters, the roof, the plumbing, or the ventilation the first place to look?
- Is the outside ground, a path, a flower bed or render bridging the wall?
- What investigation do you want before exchange, and what can wait?
Common questions
If the staining stops around skirting height, is that automatically rising damp?
No. Low-level staining is a pattern, not a mechanism. Condensation, a bridged damp-proof course, rain splash and salts can all sit in that band. Rising damp remains one possibility. Ask which cause the surveyor thinks is likely, and what single observation would show they are wrong.
How can you tell condensation from rising damp?
Condensation usually sits on the coldest surfaces, often with mould and without a tide mark from the ground. Rising damp is moisture from the ground moving up a wall, and it is only one possible reading of low-level staining. If the report does not separate the two, ask which mechanism is likely and what would prove it wrong.
Is penetrating damp the same thing as rising damp?
Penetrating damp is rain getting through the fabric from above or from the side, often from a gutter, a flashing or cracked pointing. Rising damp comes from the ground. The repairs are different, so one damp-proofing quote does not answer both.
Should you budget for a chemical damp-proof course?
Only if someone has shown that ground moisture is actually the cause and that injection suits the wall. A failed gutter, a high path or a cold unventilated room will not be cured by injecting the plaster. Get the cause named before you accept a standard specification.
Does government damp and mould guidance set a price reduction?
The guidance is written for rented-housing providers, not as a discount table for buyers. It treats damp and mould as a risk to health. Use it as a reason to take mould seriously, then price the actual repair once the cause is known.
Can you still buy if the survey only says damp?
You can, if you know which mechanism it is and what has to happen next. Buying on the word alone is how people pay for the wrong treatment. If the cause is not known, the next spend is an investigation, not a guess.
Is mould in a bedroom always rising damp?
Mould on a cold external wall or behind a wardrobe is often condensation. Rising damp does not usually appear as mould high in a room with no stain from outside. The survey should say where the mould is, and whether heating and ventilation are part of the picture.
What does a bridged damp-proof course mean?
It means something outside, such as a raised path, a flower bed or render, is letting ground moisture pass the barrier in the wall. That is not the same as a missing barrier, and it is not condensation. The first question is whether the ground or the render can be altered.
Sources
- Damp and mould: understanding and addressing the health risks for rented housing providers — GOV.UK
- Description of the RICS Home Survey Level 3 (condition rating definitions) — RICS
- Structural problems, including damp, dry rot, wet rot and woodworm (homeowner advice) — Property Care Association
- House surveys: the costs, types and benefits of an RICS home survey — RICS
Key facts
- Three mechanisms
- Condensation, penetrating damp and rising damp are different. The repair follows the mechanism, not the word damp.
- Moisture meter
- A meter reading on a home survey is not proof of rising damp. It shows a wetter surface, not the path the water took.
- What the survey sees
- A visual survey can record staining, mould and salts. It does not open walls as standard, and it does not prove the cause on its own.
- Rented-housing guidance
- GOV.UK damp and mould guidance is for rented-housing providers. It treats mould as a health risk. It is not a buyer discount.
- Wrong first repair
- A chemical damp-proof course does not mend a gutter, a cold unventilated room, or rain coming through a wall.