What does mould mean in a home survey?

What is the surveyor describing when they write mould?

Mould is a growth on a surface that has stayed damp enough, for long enough, for spores to take hold. In housing the usual pattern is condensation: warm moist air on a cold wall, a cold bridge, a window reveal, or the back of a wardrobe. It can also follow a leak, penetrating damp, or a bathroom that has no working extract. The damp page separates those mechanisms. The survey should say where the mould is and what else they saw. “Mould present” without a location is a thin sentence. Ask for the location if the report has not given it.

A condition rating, if the surveyor applies one, uses the RICS definitions of urgency and seriousness. Rating 1, 2, 3 or NI is about the building defect as they judge it. It is not a medical diagnosis and not a species list. Surveyors are not laboratories. Black mould on a bathroom ceiling and a tide mark from a failed gutter are both “damp-related” in ordinary speech and different repairs in practice.

How is the GOV.UK guidance different from a RICS rating?

GOV.UK’s damp and mould guidance is written for people who provide rented housing. It tells them to understand and address the health risks. It is official health and housing guidance. It is not the RICS Home Survey Standard, and it does not redefine condition ratings. A buyer cannot turn a paragraph of that guidance into a percentage off the price. There is no such formula on this page.

Use the guidance for what it is: a clear statement that damp and mould are a health risk, not only a decorating stain. That matters if a child, an older person, or someone with a breathing illness will sleep in the room. It does not tell you whether the cause is condensation or a leak. The survey, and any further investigation it asks for, is still how you find the cause. Landlord duties under that guidance are not the same as a buyer’s negotiation.

Why is wiping the mould off not the repair?

Cleaning removes a stain. It does not stop the moisture. If the cause is condensation, the lasting work is usually heating, insulation and ventilation, including the fans and background vents the ventilation page describes. If the cause is a gutter, a roof, or a pipe, the lasting work is that defect. A survey records the mould. It does not clean it, and it does not name a product as the cure. Do not accept “wipe it with bleach” as the repair specification. Bleach is not the finding and not the fix this guide recommends.

• Where is it, and is the surface cold, wet from outside, or under a pipe?
• Is extract ventilation present and open, or painted shut and missing?
• Did the surveyor see salts, a roof stain, or only surface mould?
• Is anyone vulnerable going to sleep in that room? That is a health reason to take the cause seriously, not a price formula.
• What investigation, if any, does the report want before exchange?

What should you ask before you treat mould as priced?

Ask the surveyor which mechanism they think is most likely, and what would change their mind. Ask the seller whether they have had leaks, new windows, or blocked vents. Fresh paint over a mould patch is a reason to look harder. Approved Document F, which is England’s ventilation guidance for building work, explains why new tight windows without vents can make condensation worse. It is not a test of this room’s air. Wales has its own building regulations. Neither document prices the clean.

If you negotiate, negotiate the cause you can evidence: a failed extract, a leaking valley, or an investigation you still need. The renegotiation page is about that discipline. A line that says “mould, therefore five per cent” is not evidence. This guide does not state a percentage.

Common questions