Depth of exterior thermal wall insulation and Window Cill depth

RomfordNavy

Does anyone have experience of fitting exterior thermal wall insulation and what happens if the window cill is not deep enough to reach over the top of it?  Is there some sort of lip that can be fitted to keep the rain from getting behind it.

FreeBear

RomfordNavy said:

Does anyone have experience of fitting exterior thermal wall insulation and what happens if the window cill is not deep enough to reach over the top of it?  Is there some sort of lip that can be fitted to keep the rain from getting behind it.

There are products available in a variety of materials and sizes. This is just one - https://ewistore.co.uk/shop/external-wall-insulation/over-sill-2-5m-140mm-depth/

Your installer should be taking care of these sorts of details (unless you are doing it yourself).

RomfordNavy

Thanks @Freebear that solves the potential problem.

At the moment I am specifying windows but prefer stub cills as they look much better.  I was just thinking about whether that would cause a problem when I come to do the thermal insulation next year.

chris_n

Far better do the insulation first and fit the windows to that layer rather than creating a thermal bridge.

RomfordNavy

chris_n said:

Far better do the insulation first and fit the windows to that layer rather than creating a thermal bridge.

In the idea world yes that would be better.  However, where I have knocked down a wall and made two rooms into one I currently have an old window installed (too small) with wooden blanks either side to stop the wind getting in.

Thermal insulation is not going to be a quick or easy job as all the old pebble-dashing will need to be chisled off first.

So in this case windows needs to be sorted before thermal insulation.

Jonboy_1984

Have you considered insulated plasterboard inside rather than touching the outside?

ThisIsWeird

Since it's likely to be just a year before the ext insul is added, is it not best to live with a too-long cill for that time? Or is your house too vain
Surely far better than an add-on cover?
Do you know what the finished thickness of insulted wall will be?

ThisIsWeird

(I am not going to correct that auto-spell)