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Lining the underside of the roof

Postby MHAD » Sun Oct 28, 2007 12:50 pm


I have a 1930's semi. The roof is tiled directly onto the timbers, no felt in those days I gather. There is wadding / horsehair & plaster type mix that is used throughout the roof on the underside of the joins between tiles.

I want to line the underside of the roof (or part of the roof) to prevent the heavy rain of dust and dirt that comes down from ruining anything I store up there.

Whatever I use will need to be fixed to the underside of the roof timbers.

A neighbour has used plastic sheeting for this purpose, however I'm nervous of restricting ventilation to the timbers by doing the same.

I've bought some breathable roofing membrane from Screwfix (Item # 95917), which is described as:

"Breathable, high-performance pitched rool underlay made from polyolefin materials, producing high vapour permability and water-resistance. User friendly.

* Eliminates Roof Space Ventilation
* Energy-Saving"

The idea is to staple gun this to the underside of the roof timbers, for about two thirds of the roof.

My question is ... what considerations should I make when fixing up the membrane, ie: is it better to have the waterproof side on the inside or outside face... I can see arguments for both ways and keep going round in circles.

The last thing I want to do is introduce any kind of mould problem to the roof timbers.

Any advice would be most appreciated.

Thanks very much.
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Postby property man » Fri Nov 23, 2007 10:02 pm

The idea of a membrane is to carry water to the guttering in the event that a tile or tiles which become damaged or missing, what you are planning to do is a waste of time it should be on top of the rafters and dressed in to the guttering using felt support trays to stop rot and flapping felt
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