Gaps round windows - fill or for drainage?

[Sparrowhawk]

Our kitchen with the hole in the wall has 2 very cold north-facing windows about 20 years old. While outside looking at the airbrick I also had a look at these windows for the first time since we moved in and spotted a few gaps.

 

Window A

 

 

The one below isn't bad at least there's plastic at the back of it (unlike window B)

 

 

Window B

 

 

 

 

The gaps at the top should be foamed/caulked I think, but the one at the bottom where the window doesn't sit on the sill? Is this a drainage path and so shouldn't be blocked?

 

Under the sills of windows A & B

Under the sill there's some gaps in the render. Hard to photograph but again something I could fill & seal or is it a place water will drain away?

 

 

Edited January 23, 2023 by Sparrowhawk

[Radian]

None of the gaps I can see there are for a purpose that I know of. Probably a residence for a few over-wintering wasps but nothing useful.

[Onoff]

Whilst "double glazing" was seen as the panacea to all cold evils, installers were often just scammers keen to maximise profit. New windows would be deliberately undersized to to allow quick fitting with no hassle. The subsequent gaps were often not filled but covered with trim. 

 

Sills were "glued" on with mastic etc.

 

The TV series White Gold was closer to the truth than you can imagine.

 

Those gaps...fill them as best as you can. I'd mask the window with tape and where you can, inject Illbrück FM330 using a proper applicator gun. When set, cut off level with the window using a sharp craft knife. Keep the windows shut whilst it's setting. Then add mastic beads all around. A Fugi Cramer tool set will help with the mastic beads. 

 

Unless you want to hack back the reveals inside and see just what atrocious gaps they've left and really do it properly.

 

I kid you not I have 1" gaps around mine. 

 

 

 

[RobLe]

Double glaze sealed window units need an external air path to the edge seal.  If you block it, then there’s a risk the seal will fail, and the window will eventually mist up internally.  This is either from water leaking in from outside, or humid air leaking in from inside.  I think from the pictures, the air path is between cill and the main unit - piccy below with red arrow.
I’ve got similar, and I kept that opening clear for that reason.  When I removed the glazing from ours (swapped for high spec), I could see small holes drilled at the bottom of the frame internally so the airspace around the dg seal connected to outside via that slot.

Totally agree with the rest, and method of foam+sealant.

 

[Jenki]

10 hours ago, Sparrowhawk said:

The gaps at the top should be foamed/caulked I think, but the one at the bottom where the window doesn't sit on the sill? Is this a drainage path and so shouldn't be blocked?

The drainage of the window should be at the front of the window, the cill / Sill sits slightly back allowing it to drain. The gap you see, as you suspect is not correct, I would seal with silicon.  Use a narrow blade to 'tool' the sealant to maintain the drainage path. not ideal, but better than water egress

 

As @Onoff has said, if the install is this poor on what you can see, I would expect far worse on the inside reveals. 

 

I would ensure you get some algicide on the render / frame to clean it before attempting to seal.

 

[gambo]

11 hours ago, Onoff said:

Those gaps...fill them as best as you can. I'd mask the window with tape and where you can, inject Illbrück FM330 using a proper applicator gun. When set, cut off level with the window using a sharp craft knife. Keep the windows shut whilst it's setting. Then add mastic beads all around. A Fugi Cramer tool set will help with the mastic beads. 

 

Unless you want to hack back the reveals inside and see just what atrocious gaps they've left and really do it properly.

 

Why mastic beads instead of some silicone and what do you mean by doing it properly?

I removed internal trim around my window some time ago because it was blowing so much air I thought someone installed a micro PIV unit under it. Turned out there were holes I could put my finger in. I filled it initially with soudal foam but haven't done a proper finishing yet because I'm still investigating what the best solution is. Would you in such case remove it and use FM330 inside too?

 

[Onoff]

Sorry, didn't mean to foam/silicone the gap where the sill meets the window!

 

This is a good shot, one of mine before it went in. See the hole in the bottom of the window? Any water in the frame comes out there and runs off the sill. 

 

 

However...your gap looks excessive, like the sill isn't tight to the frame.

 

I run a bead of silicone between the sill upstanding on the right and back of the window frame and screw the sill up into the frame. 

[Onoff]

31 minutes ago, gambo said:

Why mastic beads instead of some silicone and what do you mean by doing it properly?

 

I meant a bead of mastic as in silicone out of a tube. 

 

Do it properly, as in take the glued on beading off internally or hack the reveals off to expose the damn great gaps.

 

Your experience sounds similar to mine! I reckon the old wooden windows were less leaky! 😂

 

 

 

[gambo]

47 minutes ago, Onoff said:

 

Do it properly, as in take the glued on beading off internally or hack the reveals off to expose the damn great gaps.

 

That's the plan but trying to understand what to be prepared for and what to use. Mrs doesn't like when I rip off something in a middle of the house and leave it for couple months

I'm thinking about removing plasterboard in window bay to see if there is a cavity gap I could fill, there is one under sill I filled with plastic wool as a temporary solution but can't feel if the bay is filled with bricks.