DIY Doctor

severe damp in loft

Postby Woltato » Fri Dec 17, 2010 3:16 pm

Moved into a house recently have noticed that there is quite a severe damp problem in the loft. On cold days the whole of the underside of the roof is wet through to the point that it drips off the roof and soaks the insulation and is even coming through the ceiling in some places. Also the wooden beams holding up the roof are getting soaked so I'm quite concerned about them rotting.

House is a 1960's semi. The loft is insulated with fibreglass above the ceiling and the actual roof is a timber frame covered with felt and tiles in the standard way. What could be causing this amount of moisture? Is it just condensation and what can I do to solve the problem.
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Simply Build It

Postby stoneyboy » Sun Dec 19, 2010 6:36 pm

Two things to check. 1 have you got a CH heater tank in the loft and is this hot when the heating is running. 2. is the loft cross ventilated and insulation clear of any vents.?
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Postby SPUD1701 » Sun Dec 19, 2010 10:34 pm


By the sounds of things it is a ventilation problem - need to to have high and low level roof ventilation - make sure insulation not blocking any ventilation at soffit and make sure ventilation available at high level, also make sure that insulation in loft is cross layered so you are not losing heat from house through thermal break as heat from inside house lost into loft will condense against felt etc due to the very cold conditions outside.
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