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Tiling over the old felt,
What are you thoughts on tiling over the old felt, still using a tile membrane directly onto the felt, then my tile battens and tiles on top. I would ensure all timbers are checked for damp and any which are unsuitable will be replaced? All insulation and batten sizes to latest specification.
Thanks for everybody answers, with regards to ventilation, this roof is a cold space and all ventilation into the roof space is via ridge and soffit vents.
The felt is stuck to ply boards, therefore do I need to remove them as well???? I have a engineer on-board to work out if my existing timbers with be strong enough to carry the extra weight
if you are thinking of installing a breathable membrane under your tiles the I can see no reason why you would want to leave the old felt as it will serve no purpose, regards Terry.
Answered 7th Sep 2012
you will need to remove it so building regs can check your timbers and insulation, while it is comendable that you have an engineer on board, since the 1st of oct 2010 it has been compusory that when you remove over 25% of any roof covering you must upgrade your thermal insulation and this must be checked by building control. breathable membrane will not work if it is covering plyboard, and ive never been able to fully check the roof timbers if the top of the timbers are covered.
Answered 8th Sep 2012
Too much of a barrier may cause condensation due to the lack of ventilation. Modern 'breathable membranes are great but if you put this directly onto old felt it defeats the object of being 'breathable'.
Answered 11th Sep 2012