Common property questions, answered

What is damp in buildings?

Damp is excess moisture that should not be there. It is worth investigating whenever part of your home is not dry to the touch, has mould growing on it, or carries a musty smell that comes back a few hours after you have aired the room.

Moisture reaches a building in more than one way, and you will hear three terms used for it: penetrating damp, condensation and rising damp. None of them is a cause. Each describes how moisture is moving through or onto part of the building, not where that moisture is coming from.

Rising damp is the most misused of the three. It describes water drawn vertically upwards from the ground by capillary action — a sponge sitting in a puddle, slowly soaking water up through the tiny holes inside it. It is misdiagnosed constantly, and the standard misdiagnosis runs the same way every time: you have rising damp, so your home needs a new damp-proof course. That is not a conclusion, because it never identifies the source of the excess moisture. Failure of an original damp-proof course is extremely rare.

• Not dry to the touch — a wall, floor or ceiling that feels cold and damp rather than simply cool.
• Mould growth — black spotting in corners, on window reveals, on ceilings or behind furniture set against an outside wall.
• A musty, earthy smell that returns once the room has been shut up again.

Penetrating damp, condensation and rising damp are routes, not causes. To solve a damp problem you first have to find where the moisture is coming from — anything that starts with the remedy rather than the source is guesswork, and it is how people end up paying twice.

What causes damp?

Finding the cause of a damp problem can be genuinely complex, and where it matters the right step is a building surveyor carrying out an investigation compliant with the Joint Position Statement on investigating moisture in traditional buildings (JPS 2022).

A good deal of it, though, is visible to anyone prepared to look. Go outside while it is raining and watch what your gutters actually do. If something does not look right, it usually is not right.

• Leaking or blocked gutters and rainwater pipes.
• Roof defects — dislodged or broken tiles, poor flashings, and open chimney pots.
• Cracked external render, poor pointing, or broken sealant and mortar around windows and doors.
• Ill-fitting doors and windows.
• Ground levels raised against external walls, so that soil or paving bridges the damp-proof course.
• Bridged cavity walls — rubble or other physical blockages left in the cavity void.
• Excess rubble beneath a suspended ground floor, which stops ventilation under the floor, wets the floor timbers, bridges the damp-proof course and blocks low-level through-wall vents.
• Blocked low-level air bricks and through-wall vents serving a suspended floor.
• Failed underground drainage, or a leaking mains water supply pipe.
• Internal plumbing leaks — beneath a bath, behind an appliance, or through failed mastic seals around a shower.
• Flooding, or a high local water table.

Most damp problems have more than one cause, and the cheap causes are as common as the expensive ones. A blocked gutter and a raised flower bed together will produce a wall that looks like a textbook case of rising damp.

How to identify structural cracks

Most cracks in a house are not structural. Plaster shrinks, new build dries out, materials expand and contract with the seasons, and decoration cracks along the joints where two materials meet. The cracks worth taking seriously have a particular character.

• Wider than about 5mm, or noticeably tapered — wider at one end than the other.
• Diagonal, and stepped through the mortar joints of brickwork rather than running straight.
• Radiating from the corners of windows and doors, which are the weak points in a wall.
• Visible in the same place both inside and outside the building.
• Getting longer or wider over weeks and months rather than staying put.
• Accompanied by doors and windows that have started to stick, floors that slope, or a bay window pulling away from the main wall.
• Close to a mature tree, a recently removed internal wall, a drain run or the junction with an extension.

Surveyors classify crack width using BRE Digest 251, from category 0 (hairline) through to category 5 (over 25mm). Categories 0 to 2 are generally aesthetic and filled at redecoration; category 3 and above warrants investigation. Where movement might be ongoing, the answer is usually monitoring with tell-tales or crack gauges over six to twelve months, which distinguishes seasonal movement from progressive movement. Do not fill and redecorate before it has been assessed — you lose the evidence.

Mould and your health

Mould growing indoors releases spores and fragments into the air you breathe. For most people the effect is irritation — a cough, a blocked nose, itchy eyes, disturbed sleep. For anyone with asthma or another respiratory condition it can be considerably more serious, and damp homes also suit dust mites, which are a separate trigger in their own right.

The people most affected are infants and young children, older people, anyone with a respiratory or allergic condition, and anyone whose immune system is suppressed. If someone in the household falls into one of those groups, damp and mould should be treated as urgent rather than cosmetic.

• Damp and mould are assessed as a hazard under the Housing Health and Safety Rating System, which councils use to act on unfit housing.
• In England, the Homes (Fitness for Human Habitation) Act 2018 lets tenants take a landlord to court over a property that is unfit, including because of damp and mould.
• Awaab's Law sets time limits for social landlords in England to investigate and put right damp and mould hazards once they are reported.
• Wiping mould away or painting over it with a fungicidal coating deals with the growth, not the moisture that fed it — it will return, usually in the same place.
• Fixing the cause means some combination of removing the water source, improving ventilation, warming cold surfaces and changing how the space is used and heated.

What is a building survey?

A building survey — a Building/Level 3 surveys — is the most thorough standard inspection available on a home. The surveyor examines the accessible parts of the structure and fabric: roof coverings and roof space, chimneys, walls, windows and doors, floors, ceilings, internal joinery, insulation, dampness, timber condition, drainage and the visible parts of the services.

The report does more than list what is wrong. It describes how the property is built, identifies defects, explains their likely cause and what happens if they are left, and sets out repair options with a sense of urgency and sequence. That last part is what makes it usable — it tells you what to do first.

• It is non-intrusive: floor coverings are not lifted, structure is not opened up and services are not tested, although moisture meters, thermal imaging and a borescope are used where they help.
• It is not a valuation. Some surveyors will comment on value or rebuild cost separately, but a lender's valuation is a different exercise entirely.
• It is not a guarantee against every unseen defect — no visual inspection can be — but it is the closest you can get without opening up the building.
• It suits older properties, unusual or non-standard construction, homes that have been extended or altered, properties in poor condition, and any house you intend to work on.

Should I get a survey before buying a house?

No, a survey is not compulsory — and that is exactly why so many buyers skip one and regret it. The valuation your lender carries out is for the lender's benefit, confirming that the property is adequate security for the loan. It is not an inspection of the building on your behalf, and it will not tell you that the roof has ten years left in it.

The principle in a house purchase is caveat emptor: buyer beware. Once you exchange, the condition of the property is your problem, whether or not you knew about it. A survey costs a few hundred pounds; a re-roof, a damp programme or an underpinning scheme costs many thousands.

• The case for one is strongest on older properties, anything extended or altered, homes with visible cracking or damp, flat roofs, and streets lined with mature trees on shrinkable clay.
• Cash buyers should be the most careful of all, because no lender is looking at the property at any point in the transaction.
• New builds and recent renovations are not exempt — unregulated DIY work and unfinished builder's work are both common findings.
• Findings are also a negotiating position: a costed defect list is the most persuasive thing you can put in front of a seller before exchange.

What survey do I need?

The right level depends on the age, construction and condition of the property — not on how much you are paying for it. A modern flat and a Victorian terrace at the same price need different things.

• Home Buyer/Level 2 Survey: conventional homes, roughly under a century old, in reasonable condition. The most common choice for a straightforward purchase.
• Building Survey/Level 3: older, altered, extended, neglected or unusually built properties, and anything you plan major work on.
• Damp and mould survey: where a specific problem already exists and you need the cause diagnosed rather than the whole house reviewed.
• Snagging inspection: new-build homes, ideally before completion and certainly within the first two years.
• Buy-to-let inspection: purchases and portfolios where compliance and running condition matter as much as defects.
• Specific defect or structural report: a known crack, movement, timber or roof problem investigated on its own.

How long does a building survey last?

This is really two questions, and both matter when you are planning around a transaction.

Time on site: a Home Buyer/Level 2 survey on an average house typically takes around one and a half to three hours. A Level 3 building survey usually takes three to eight hours, depending on size, age, access and how much there is to record. The written report generally follows within three to ten working days.

How long it stays valid: a survey has no formal expiry date, because it is a record of the property as it was on the day of inspection. In practice, buyers, sellers and lenders treat one as current for around three to six months, and mortgage valuations are commonly given a three-month life.

• If the transaction drags on well beyond that, the report is still useful, but it no longer reflects the property today.
• Ask about a revisit after severe weather, after a period standing empty, or after any works have been carried out.
• Keep the report after completion. For the first few years it doubles as your maintenance plan.

What happens after a survey?

A report can run to fifty pages or more, and the first reaction to a long defect list is often alarm. Nearly every property produces one. The work is in sorting it.

• Read the summary and any urgent items first, then go back through the detail section by section.
• Separate the list into three: things that threaten safety or weather-tightness, things that need doing within a year or two, and ordinary maintenance.
• Call the surveyor. Most include a follow-up conversation at no extra cost, and fifteen minutes on the phone is worth more than a second read.
• Commission any further investigation the report recommends — a structural engineer, a drainage CCTV survey, an electrical test or a timber specialist.
• Get quotations for the significant items before you decide your position, so any renegotiation is based on figures rather than fears.
• Then choose: proceed, renegotiate the price, ask the seller to carry out the work before exchange, or withdraw. All four are legitimate outcomes.

Whatever you decide, do it before exchange of contracts. After exchange you are committed, and the report becomes a repair plan rather than a negotiating position.