Loft Conversions Question

Loft felt

I have an old house where in the loft there is no felt under the tiles, and the mortor that is attached to the back of the tiles is now all falling out, is it ok to replace the mortor with expanding foam or something of a similar product as i can't aford to have felt put into place.
would be very greatful if someone could advise me on this loft felt matter.

3 Answers

Best Answer

Dont use foam, the correct method is called torching, this is a lime mortar mix with horse hair added, the roof still needs to breathe.
This isnt an expensive job, dont worry about absence of loft felt as its only a secondary precaution against draughts and driving rain.
There are still thousands of roofs that were done this way and still in good water tight condition.

Answered 4th Jan 2012


Member since 29 Oct 2008

I would advise you NOT to use expanding foam. The foam will spill out on to your loft roof and look an eyesore - not to mention the fact it is a nightmare to clean off. Are you looking at replacing the mortar because the loft's roof is leaking or to hold the tiles/slates in place?

If the roof leaks slightly ie the odd drip, I wouldn't worry. Because the roof has no felt there is sufficient draught to dry the roof out.
Hope this helps. It is quite difficult to advise with such limited information.
J Chappell Joinery and Renovation

Answered 4th Jan 2012

J Chappell Joinery

Member since 30 Jul 2008

This is known as back pointing it is sand cement and horse hair. Its the original way (before loft felt) to stop draughts blowing under the slates. I would recommend re doing over foam, as if you need to change a slate if it has foam it is near on impossible to replace. Also foam traps moisture and can end up causing more damage to the timbers of your roof structure.

Answered 4th Jan 2012

Northwest Roofing and Building Maintenance

Member since 9 Jun 2011

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