Why does an empty flat get mouldy?

No heating, no ventilation and residual moisture in the fabric. Surfaces stay cold enough for condensation to form and nothing dries.

Does mould-resistant paint solve it?

No. It slows regrowth on a surface that has been dried and treated, but it does nothing about the cause.

Void property clearance

Damp and mould in an empty property

Unheated, unventilated and closed up — the classic combination

The short answer

Empty properties grow mould because heating is off, windows stay shut and any moisture in the fabric has nowhere to go. The fix is background heat, controlled ventilation and time, plus finding any genuine defect such as a leaking gutter or failed roof detail. Painting over mould without drying and treating the surface guarantees it returns within weeks.

What the work involves

Establishing whether the moisture is condensation or a defect, running low background heat and ventilation, treating affected surfaces with a fungicidal wash, then redecorating once readings are stable.

Rules and responsibilities in Scotland

Where the property will be let, mould affecting the fabric puts it outside the Repairing Standard. Insurers may reduce cover on properties left unoccupied and unheated for extended periods.

What commonly goes wrong

Sealing a damp property up completely to save heating cost, and using mould-resistant paint as a substitute for drying the wall out.

What it usually costs

Indicative ranges only, to help you judge a quote. They are not an estimate for your property — only the business doing the work can give you that.

Background heating during a void is cheaper than the redecoration a mould outbreak causes.
Dehumidifier hire for a few weeks is inexpensive compared with replastering.
An independent damp diagnosis avoids paying for an unnecessary damp-proof course.

What to do, in order

1Check outside first — gutters, downpipes, roof, pointing and ground levels.
2Set the heating to a low continuous background temperature.
3Ventilate consistently rather than opening everything on one dry day.
4Wash affected surfaces with a fungicidal treatment before decorating.
5Re-check moisture readings before redecoration rather than working to a deadline.

Local detail for the Lothians

Edinburgh's solid stone walls hold moisture for longer than cavity construction, so drying out takes weeks rather than days.
Top-floor tenement flats show mould at wall-head and around dormer cheeks where insulation is thin.
Long summer voids in student flats with heating switched off are the most common cause locally.

When you need a professional

An independent chartered surveyor should diagnose persistent damp before any treatment is bought.

Common questions

Why does an empty flat get mouldy?: No heating, no ventilation and residual moisture in the fabric. Surfaces stay cold enough for condensation to form and nothing dries.
Does mould-resistant paint solve it?: No. It slows regrowth on a surface that has been dried and treated, but it does nothing about the cause.

Lothian Property is a property information and professional-introduction service operated by Maybury Scotland Limited. Lothian Property is not an estate agency. Where requested, we may connect homeowners with independent estate agents and other property professionals. How we work.

Winterising an empty property
Heating, draining down and frost protection through a Scottish winter.
Insuring an empty property
Why standard cover lapses when a property is unoccupied, and what insurers require instead.
Void decoration and repairs
The quick, high-return repairs and repainting that make a property let or sell faster.

Last reviewed 4 September 2026.