Insulating where joists meet the wall

[Richardk]

We have a completely uninsulated roof which is a project I'm about to tackle. Upon closer inspection it seems that where the roof joists meet the wall there is in some instances a fair amount of gap to the outside world. The largest I've found so far is say 5cm by 5cm or so.

What substance should I use to fill this? Mortar or foam? I'm conscious that the latter may be strong enough to push the tiles up if used too enthusiastically but then the holes are quite big for just mortar....?

Appreciate your views.
Richard

[Alcazar]

We've had an old barn roof renovated (replaced), and some gaps are MUCH bigger than yours

Our roofer said to fill 'em with mortar and stone. At the mo we get an owl in that sh*ts everywhere, and drops pellets where it hasn't sh*t yet, , and a black redstart nested in there last spring, so any internal work got stopped.

Personally, if it's out of sight and will be under any internal insulation, I'd use foam for the smaller gaps, but do be aware as to how much you put in!

Alcazar

[Alan Zoff]

Also bear in mind before overdoing it that roof spaces require adequate ventilation. Otherwise you can have condensation and associated damp rot problems. (I am not a builder in any sense of word but was told that sealing up of all the gaps was the cause of roof problem with our UK house.)