Straight answers · Damp in UK homes
Damp gone.
Cause and all.
You have a wet wall and three companies telling you three different things. Here you find out which kind of damp you are actually looking at. What is putting the water there. And which fixes deal with that cause instead of covering it up.
- What it actually is
- What fixes it
- What it should cost
Start with what you can see
27 in-depth guides, and counting
Rising damp, and the test almost nobody runs
What rising damp actually is, why the moisture meter used on almost every survey cannot confirm it, and the laboratory method the British Standard points to instead.
Read it →Penetrating damp, and the wall that was never built for your weather
Water coming in sideways is a building fault with a location, not something the wall has caught. The exposure zone your wall stands in, and what the regulations say it needs.
Read it →Damp meter readings, and why there is no acceptable number
The reading almost every damp quote in the country is built on is a wood measurement. What the meter is really telling you, and what would settle the question properly.
Read it →Mould on walls, and why it keeps coming back
Cleaning it off is the easy part and it is not the part that matters. What the official guidance says about removing mould, about bleach, and about who is to blame.
Read it →Condensation, and why a dry wall still grows mould
The number that decides whether mould grows is not the dew point. The humidity to aim at, and how to tell condensation from the two kinds of damp people pay to have treated.
Read it →Damp proofing costs, and the half of the quote nobody shows you
The per-metre rate people search for is the smallest line on the bill. What the published guides say, where they disagree, and what a damp quote quietly leaves out.
Read it →Damp surveys, and why the free one exists
A home survey is built to pass a damp question onward, not to answer it. What RICS actually promises, what the free survey is for, and when paying is the cheap option.
Read it →The damp proof course, and the two minutes that could save you thousands
Your damp proof course has a required height above the ground and you can check it yourself with a tape measure. How the whole system works, and what defeats it.
Read it →What a dehumidifier actually fixes, and what it only hides
An excellent machine for one of the three kinds of damp and close to useless against the other two. What it costs to run, and the room temperature that stops it working.
Read it →Heating and damp, and the mechanism nearly everyone gets backwards
It is not that warm air holds more moisture. What governs mould is the temperature of your coldest surface, and the cheapest way to raise it is often not the boiler.
Read it →Ventilation for damp, with the numbers nobody gives you
Approved Document F publishes a rate for every wet room in the house. Here they are, plus the two ventilation defects that pass a visual check.
Read it →The survey said damp. What that actually means, and what to do next
Further investigation recommended is the survey working, not the surveyor hedging. Why a RICS survey cannot settle it, and who the free damp survey is really working for.
Read it →Selling a house with damp, and the question the form never asks
Damp appears once in the Property Information Form, and not where you would expect. What that means for what you must say, and where the liability actually sits.
Read it →Damp and your mortgage, and what a retention actually involves
Damp rarely stops a mortgage. It changes its shape, through a retention. The steps, the re-inspection fee, the release window, and the cash-flow trap nobody mentions.
Read it →Basement tanking costs, and why three quotes never compare
Every published price for this job is per square metre, and nobody says which square metre. The two systems sold as tanking, what each cannot do, and the yearly cost no one prints.
Read it →Condensation on windows, and why the glass is the gauge not the fault
Your window is the coldest surface in the room, so it is where the air shows its hand first. Which glazing sits below the dew point of a normal room, and where the water goes once you have wiped it off.
Read it →Condensation in double glazing, and the two versions that are not a fault
One phrase, three different faults, and two of them are not faults at all. Which is which, what is actually inside a sealed unit, and what it costs to put right.
Read it →Damp proofing guarantees, and the six questions the trade next door answers in public
A guarantee is the one line on a damp quote nobody prices. What the published terms actually say, what voids one, and the six questions the trade next door answers in public.
Read it →Is black mould dangerous, and the word the guidance never uses
Yes, and the harm the UK guidance describes is respiratory, not a poisoning. What seven searched claims actually rest on, which named body says each, and the eight groups it puts most at risk.
Read it →Musty smell in the house, and why the nose gets there first
The smell is not the problem, it is the earliest reading you own. What it physically is, why it arrives before anything is visible, and how to trace it to a place.
Read it →Cavity wall insulation problems, and the table that says which walls should have had it
A cavity exists to stop water crossing it, and filling one changes that on purpose. Which walls the regulations recommended it for, and what the 25 year guarantee covers.
Read it →Mould on clothes, and the wardrobe that put it there
The jumper is not the problem. Why a wardrobe on an outside wall is the worst place in a bedroom, what the conservation bodies do before anything wet touches the fabric, and when a garment is past saving.
Read it →PIV units, and the question that decides whether yours is worth buying
It acts on moisture in your air, so it is a real answer to condensation and no answer at all to the other two kinds. The makers' own wattages, costed.
Read it →Dry rot, and the number that makes the name a lie
Dry rot needs wet wood. A spore cannot germinate below 30% moisture content and decay stops below 20%. How to tell it from wet rot, and what the bodies disagree on.
Read it →Woodworm treatment, and the hole that proves nothing
A flight hole is where a beetle got out, sometimes decades ago. What counts as evidence of a live infestation, which beetle you have, and why dry timber deals with most of it.
Read it →Wet rot, and the cut-back distance nobody can show you in writing
Wet rot stays in the timber that is wet, so the fix is carpentry plus a repair to the water. The published cut-back distances, and which rot each one was written for.
Read it →Condensation in the loft, and why it is coming up from below
Water on the felt is almost never water coming in. It is your house leaking warm wet air upwards. The published ventilation figures you can check your own roof against, and what five specific patterns mean.
Read it →No survey to sell you.
Nearly everything written about damp in this country comes from someone who wants to come and do the work. Here you get the answers I would give you over the fence. What the wet patch actually is. What is putting the water there. And what I would do about it if it were my wall.
Nobody pays for the verdicts
No damp-proofing firm owns this site, and nothing here is a paid-for opinion. When a treatment is the wrong answer to your problem, the page says so. If a recommendation ever earns me anything, the page discloses it plainly, right where it sits.
Cause first, always
Every answer starts with the same question. Where is the water coming from? Treat the wall instead of the source and it is wet again by next winter. Only now you have paid for it twice.
No waffle
Short answers first, the why underneath. You leave every page knowing what to do next, not with ten tabs open.
The questions everyone asks
Watch when it changes rather than what it looks like. Condensation gets worse in cold still weather with the room in use. Penetrating damp gets worse during and after rain. All three leave the same dark patch, which is why photographs settle nothing.
Condensation, penetrating damp and rising damp. And a fourth possibility nobody lists: salt left in the plaster. It pulls moisture straight out of the air and reads damp with nothing leaking, rising or condensing.
No, and that is not a technicality. The number on a handheld meter is a wood moisture scale, and the manufacturers say so in their own documentation. There is no published acceptable figure for masonry because the scale was never describing masonry in the first place.
The honest answer is that the visible signs do not separate it from anything else. BS 6576 puts it plainly: surface measurements cannot alone give proof of rising damp. A tide mark and a high meter reading are equally consistent with salt in the plaster, which draws moisture from the air once humidity passes about 75%.
Because it is usually provided by the company that would quote for the treatment. That is a structural conflict rather than an accusation, and it exists because a RICS home survey is built to pass the question on: RICS says its surveyor does not open up the fabric and uses a damp meter.
Nobody agrees, which is the useful thing to know before you judge a quote. Published guides put chemical DPC injection at £60 to £90 a metre and at £70 to £120 a metre, and a whole-house average at £1,250 and at £1,500 to £4,000. Inner London runs 20 to 25% above those.
They deal with condensation and nothing else. Pulling the room humidity down genuinely helps, because what decides whether mould grows is the humidity at the wall surface rather than in the middle of the room. But a dehumidifier cannot do anything about water arriving through the wall.
See all questions, or got one that is not here? send it over and the useful ones get a proper page.