massive gap under window

Tea drinker

Honking great gap under the window sill, not sure what do do here. There is some air coming through meaning there is a an exterior problem. I guess it needs insulation , but should I just fill it on the inside and insulate outside, or should I insulate from inside also. What to use - maybe expanding foam?
I'll leave it slightly recessed as I'll need to put some filler and finish it nicely.
It's an aluminium window frame

As regards the outside, it's a bit shoddy looking, there's a sort of facia bord covering the base of the window, and it looks like some dodgy repairs were carried out there. There should be a seal of some kind behind the board, be it plaster or whatever, and insulation behind that? Does there need to be air gaps?

sky6

You could use Foam filler or even sand and cement. Then finish off with plaster.
I'm not sure the amount of foam insulation required would make any difference
in the context of Insulation.
The Second picture I can't quite make out the situation from the Photo but if there is something to cover the joint then again foam would. Otherwise I'd be inclined to use sand and cement.
Maybe finish off with a bead of Silicone to make sure no air is getting through.

liveandnetural

http://www.youtube.com/watch?v=j1O3L0RKbuQ

Fries-With-That

Tea drinker wrote: »

Honking great gap under the window sill, not sure what do do here. There is some air coming through meaning there is a an exterior problem. I guess it needs insulation , but should I just fill it on the inside and insulate outside, or should I insulate from inside also. What to use - maybe expanding foam?
I'll leave it slightly recessed as I'll need to put some filler and finish it nicely.
It's an aluminium window frame

As regards the outside, it's a bit shoddy looking, there's a sort of facia bord covering the base of the window, and it looks like some dodgy repairs were carried out there. There should be a seal of some kind behind the board, be it plaster or whatever, and insulation behind that? Does there need to be air gaps?

Would it be possible to stand back a few feet and take the pictures again.

One of the pictures shows a repair under ? the window where an area has been patched with deck boards.

The other picture with your finger show a gap under a window board, my concern would be how these gaps appeared and possibly repairing this problem (which may be evident from further pictures) before attempting to fill the gaps with anything.

I'm wondering is this a hollow wall type building (portacabin) or similar structure.

Tea drinker

Hi folks, been busy with moving in etc... she's driving me fairly hard so didn't have much chance to update the thread :-)

attached a pic from a bit further back, you can see the window faces onto a terrace area which is decked, and the join from the terrace to the window uses what seems a vertical piece of decking. The window runs practically the length of the apartment with maybe a 6 foot section of wall either end.
Behind that decking plank there is what appears to be a membrane which is perhaps fixed on top but not on the bottom, it just hangs down and can be lifted by hand. A second layer of felt is underneath this as well.
You can see it's quite possible to put your hand in quite far between the window and membrane.
I'm not sure if this should be airtight, but I don't think it is. How porous it should be.... well I guess the blinds shouldn't move on windy days.

Fries-With-That

If it was mine to work on, what I'd do is take off the deck board that's being used as an upright board.

Clean off all old filler, silicone and dirt and dust. The black plastic membrane looks like DPC. I'd be inclined to put a bed of mastic on this between it and the bottom of the window. I'd then use expanding foam under the DPC from the inside and the outside of the house.

I'd replace the deck board having cut the top edge at an angle to allow rain running down the window to run off the board rather than down behind it. I'd also silicone the board along its top edge where it contacts the window and the wall.

Its not mine and I'm not an expert but that's my DIY solution.

Tea drinker

Thanks, I'll have to look at somehow sealing and insulating it, the coldest rooms by far face these windows. I might look into getting the architects drawings for the apartment, the council should have those? Handy to have anyway.