Airtight tape on 3g windows. Or not?

[LaChab]

@Chanmenie Thanks

[LaChab]

@Mike I must confess I haven't considered the cills as much as I perhaps should have! It's been a bit of a journey deciding on the window design.

The Internorm salesman showed us some aluminium cills that looked quite good. They attach to the "extra lump" that appears underneath the window. They've got upstands at each end, which makes them quite robust. Much better than the rather flimsy ones we've got now.

I've only arranged for the sides and top of the reveal to be rendered to stop beads. The bottom is just being finished with a stop bead on the vertical surface. Then I was going to paint the bottom reveal with liquid membrane, as I've seen on here, and possibly even add a strip of actual membrane.  The windows are going to be 120mm inset, so about 150mm cills. 

Hope that makes sense!

[Mike]

1 hour ago, LaChab said:

I must confess I haven't considered the cills as much as I perhaps should have! It's been a bit of a journey deciding on the window design.

The Internorm salesman showed us some aluminium cills that looked quite good....

I've only arranged for the sides and top of the reveal to be rendered to stop beads. The bottom is just being finished with a stop bead on the vertical surface

Sounds good, though I was thinking of something a little different!

 

A sill would normally project through the render, where the red arrow is below (looking at the outside now, not the inside). But if you're rendering before the window's fitted, the render will be in the way, unless you make some provision for it, or have another solution - stone sub-sill maybe?

 

[Gone West]

13 hours ago, G and J said:

Ah, as we are.  What material did you put on as the outer leaf?  We are having masonry downstairs and timber clad upstairs and I’m struggling to work out exactly where to place the windows with respect to the frame.

Our frame was a 350mm timber I-beam portal frame which was fully clad with cedar with the exception of a brick slip plinth. The windows and doors were set halfway into the frame and were strapped onto OSB fillers fixed to the I-beam web.

[LaChab]

@Mike You're right, it does look a bit of a potential problem.Leaving the render until after the windows are fitted would be a real pain though. 

I checked with Internorm, and they were ok with doing the render first, so I didn't think much more about it!

I'll bring it up with the surveyor when they come to measure up.

[Chanmenie]

46 minutes ago, LaChab said:

@Mike You're right, it does look a bit of a potential problem.Leaving the render until after the windows are fitted would be a real pain though. 

I checked with Internorm, and they were ok with doing the render first, so I didn't think much more about it!

I'll bring it up with the surveyor when they come to measure up.

I fitted windows first then the render 

[Russell griffiths]

@LaChab if you render the reveals, how will you prevent water going down the sides of the window cill. 
 

from the cills we purchased I thought they went in first and the render came down onto the cill. 

[Russell griffiths]

[LaChab]

@Chanmenie @Russell griffiths Yes, cills first sounds much better. Trouble I hink that would mean having a second lot of scaffold just to do the sides of the reveals. 

I was intendiung to use the liquid membrane you like before the cill is fitted, so perhaps that and something suitable (silicone? tape?) between the upright side of the cill and the side of the reveal might be ok.

Wouldn't be ideal, but probaly waterproof........

The reveals havn't been rendered yet (weather!), so if I found the section of the cills I could "block of" just the lower bit of side render, then patch it in by ladder after the cills have been fitted.

[LaChab]

@Russell griffiths Yes, those pictures make the problem a bit obvious!

Did you cut into the foam for your cills? 

We're using thin coat render, so wouldn't be a huge overlap without going into the foam, but still be a big improvement.

[G and J]

5 hours ago, Gone West said:

Our frame was a 350mm timber I-beam portal frame which was fully clad with cedar with the exception of a brick slip plinth. The windows and doors were set halfway into the frame and were strapped onto OSB fillers fixed to the I-beam web.

Ah I see.  Ta for getting back to me. We’re using a 140mm stud frame. 

[craig]

On 21/01/2025 at 20:22, LaChab said:

The installer's almost insisting on 10mm, which seems ott to me.

Perfect and correct tolerance in most scenarios, 10mm with a cranked bracket is standard, especially when sitting behind the ingo/check reveal. If between the block/brick then you’re looking for 5mm and not 10mm but the detail here is important as 10mm might be best.
 

The problem is the nozzle for the gun is 5mm.

Edited January 27 by craig

[LaChab]

@craig Thanks for the input.  No check reveal, just 15mm stop beads on the Jackon closure. It was mainly the fact that they were unable to guarantee the work if they fitted a "side attached" membrane, despite charging £1k.I've now asked for a quote from another Internorm dealer who actually offer a membrane as an option, although it's still £1k!.

[craig]

20 minutes ago, LaChab said:

@craig Thanks for the input.  No check reveal, just 15mm stop beads on the Jackon closure. It was mainly the fact that they were unable to guarantee the work if they fitted a "side attached" membrane, despite charging £1k.I've now asked for a quote from another Internorm dealer who actually offer a membrane as an option, although it's still £1k!.

 

Airtightness products are not a cheap option but you are installing good windows and doors, not spending the money on the i3 Illbruck around the window in my opinion would be the wrong decision. We are also adding a fourth to our installs now and that is ME501 VV 140mm externally. I'm not a fan of face fixing but it is fine to do it, I'd much rather it was on the sides and pinched in the corners. 

Why face fix? Side fixing means it gets in the way and it is easier to face fix after the window is added to the opening (in my view a lazy way).

Edited January 27 by craig

[LaChab]

@craig Thanks for the support for side fix. I went for the original supplier because they're "Internorm Platinum", and I thought they would make the best job of installation. so I was really suprised when I enquired about the fitting spec and found that they just used 330 foam with no membrane / tape at all. As I've said, I think face fix is difficult to conceal behing the plasterboard, especially with a 10mm gap. Hopefully the "new" supplier will work out ok with "i3" sealing.