
Mould in New Builds: The 2025 Homeownerโs Guide to a Healthy, Dry Home โฏ๐ ๏ธ๐ฑ
Quick stat: Around 6โฏmillion English homes now suffer damp or mouldโthatโs more households than own largeโscreen TVs! ageing-better.org.uk
Brandโnew houses shouldnโt make that listโbut many do. Letโs unpack why, fix existing problems, and futureโproof your home so you never smell that musty whiff again.
Why Are We Seeing Mould in BrandโNew Homes?
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Lockedโin construction moisture (plaster, concrete, timber arrive wet).
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Design shortcutsโminimal eaves, cold bridging, inadequate cavity insulation.
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Modern living habitsโhigh occupancy + energyโtight envelopes = trapped humidity.
High indoor RH above 70โฏ% is a red flag; mould colonises surfaces in as little as 48โฏhours. HSE
The Damp Triangleโข โ Three Root Causes & How to Break Them
Triangle Point | Common Triggers | Fast Fix | LongโTerm Strategy |
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Moisture Source | Wet screed, cooking steam, unvented dryers | Run extractor fans 20โฏmin past use | Install humidityโsensing fans & check plumbing |
Surface Temperature | Cold bridging at lintels & corners | Add insulated plasterboard | Specify thermal breaks in future builds |
Airflow | Blocked trickle vents, furniture tight to walls | Open vents, move wardrobes 50โฏmm away | Commission a wholeโhouse MVHR system |
RoomโbyโRoom Danger Zones ๐
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Bathrooms: ceiling mould above showers; check that fan hits โฅ15โฏl/s.
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Kitchens: backs of cabinets; ensure cooker hood is ducted outside.
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Bedrooms: behind wardrobes on external wallsโkeep gaps for airflow.
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Lofts: cold roof deck where insulation is missing or displaced.
Pro tip: Our inspectors use FLIR thermal cameras to visualise hidden cold spots before mould appears.
Materials That Matter
HighโRisk | LowโRisk | Why It Matters |
---|---|---|
Standard gypsum board, paperโfaced insulation, unโtreated softwood | Cement board, closedโcell PIR, kilnโdried & treated timber | Some substrates feed mould; others deny both food and moisture |
Ventilation & Drying Roadmap (Firstโฏ90โฏDays After Completion)
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Weekโฏ1โ4: Run heating at 18โ20โฏยฐC, trickle vents open 24/7.
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Weekโฏ2โ6: Schedule daily shock ventilation: 5โ10โฏmin wideโopen windows.
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Weekโฏ4โ12: Dehumidifier on target RH 55โฏ% while plaster cures.
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Anytime: Wipe condensation from windowsโdonโt let it drip onto sills.
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Quarterly: Clean extract fan grilles; dust lowers efficiency by 15โฏ%.
These steps mirror NHBCโs latest โMoisture in New Homesโ guide. nhbc.co.uk
Health, Warranty & Legal Essentials
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Respiratory risk: 60โฏ% of UK occupants report mouldโrelated symptoms. Landlord Today
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โAwaabโs Lawโ fastโtracks repairs of damp and mould hazards within social housing, raising the bar for all developers (full rollout by 2027). The Guardian
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NHBC treats mould as a latent defect if linked to design or workmanshipโlog issues within your 2โyear builder warranty.
DIY vs Professional InspectionโWhen to Call Us
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Condensation on inner surfaces after two heating cycles
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Visible mould larger than an A4 sheet
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Persistent RHโฏ>โฏ65โฏ% despite ventilation
Our DroneโtoโBasementโข survey pinpoints moisture ingress, includes a FLIR heatโloss scan, and delivers an NHBCโreferenced snag report within 48โฏhrs. Book today and weโll deduct your ยฃ50 booking deposit from the feeโguaranteed.
๐ See a real client case study
FAQโฏ(2025 Edition)
What causes mould in new builds?
Trapped construction moisture, inadequate ventilation, and cold bridging create a perfect habitat.
Should I โair outโ my new home every day?
Yesโ5โฏminutes of wideโopen windows twice daily balanced with consistent heating keeps RH below the critical 65โฏ% mark.
Which building materials are most mouldโresistant?
Cement board, closedโcell insulation, and treated timber outperform standard gypsum and paperโlined products.
Can developers refuse mould warranty claims?
They can try, but evidence from an independent RPSA surveyor (thatโs us!) plus NHBC tolerances usually wins the case.