Condensation in Loft Conversion
Moisture forming on windows, walls, or the inside of the roof slope in a loft conversion.
What Is Causing This?
- 1Inadequate ventilation in the converted space
- 2Vapour barrier missing or incorrectly installed
- 3Warm moist air from below rising and meeting cold surfaces
How Urgent Is This?
This should be fixed in the coming weeks. Leaving it may allow the problem to worsen and cost more to repair.
What Needs to Be Done
A specialist will improve ventilation, check the vapour barrier, and may add ventilation gaps above the insulation. Mechanical ventilation or a positive input ventilation unit may be recommended.
How Much Will It Cost?
National average estimate
Labour: £16,667 – £33,333 | Materials: £8,333 – £18,333
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Ask a QuestionHow to Prevent This
Keep the loft room well ventilated. Use trickle vents on loft windows. Ensure the vapour barrier is continuous with no gaps or tears.
Related Problems
Visible moisture, water droplets, or damp patches on the underside of the roof felt or rafters in the loft space.
A loft conversion room that is noticeably colder than the rest of the house, even with the heating on.
Black or dark green spots spreading across the bathroom ceiling, sometimes extending down the walls.
Other Loft Conversion Specialist Problems
The floor in a loft conversion feels springy or bouncy when walked on, sometimes with visible flex.
A loft conversion room that is noticeably colder than the rest of the house, even with the heating on.
The loft conversion becoming uncomfortably hot in summer, making it difficult to use or sleep in.
The staircase to the loft conversion feels dangerously steep or does not meet building regulations.