Mould, condensation and tiny insects — is this normal in a new build?

New builds hold a lot of construction moisture and take a year or more to dry out. Some of what you’ll see is normal — and some of it is worth pushing your developer about.

Mould on skirting boards or behind kitchen units

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Common in year one where drying-out meets cold spots. Ventilate well and wipe it down — but if it keeps returning, report it to your developer’s customer care: developers here have replaced mouldy skirting boards and kitchen unit backs, and have supplied dehumidifiers on request. Don’t accept “it’s just condensation” for recurring mould in the same spot.

Tiny light-brown insects (booklice)

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Booklice thrive on the microscopic mould that grows on damp, drying plaster. They’re harmless and disappear once the house dries out — they’re not a hygiene problem. In summer heat you may also get thunder flies (tiny black slivers) coming in from outside; fly screens on windows are the practical fix.

Cracks in plaster

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Small shrinkage cracks are normal as the house dries and settles — see the Welcome Pack section on new-build quirks. Report them as you find them, but expect the developer to fix them in one go at around the 12-month point, once settlement has largely finished. The rule of thumb for when a crack is serious rather than cosmetic: wider than a pound coin’s edge (about 3mm) — report those promptly and mention the width.