Gap between window and sill - new uPVC windows

[ST1978]

Hi all. I'm in the process of having some new windows and sills fitted by some local fitters after deciding it was too much to take on myself. Most of the windows are in now but quite a few of them have gaps between the top of the sill and the underside of the window frame. This isn't the drainage gap...this area is fine. Most guides I've seen suggest that the sill should be sealed to the underside of the windows especially at the ends to prevent water finding a path to the wall. The fitters haven't used any sealant between them, but they say this is fine and normal in the trade. The hasn't been attached to the frame by screwing it up from underneath, but by screwing down through the frame into the top of the sill, which clearly hasn't worked very well. They're proposing to put longer screws in to catch the bottom of the sill too and pull it tighter. This doesn't sound right. FENSA seems to suggest that the window and sill should be well sealed together, as does the Eurocell (manufacturer) fitting guide. These guys are CERTASS registered, which I assume have similar standards? What do you all suggest? Is this normal? Or good enough? Will water be able to get to my house? Can they rectify without taking the windows out? The images are from a 1.8m wide window, but there are similar gaps on some 2.4m wide ones and also narrower ones. There are also some windows with 15mm is gaps underneath them which are foam packed, which they intend to back-fill with mortar. Any advice is greatly appreciated.

[Onoff]

Sorry, bodgers. In and out, quick as.

 

Imo bits of paper and certs can mean very little. Easy to buy into a club.

 

A big problem is that as they've put a screw in from the top (again a bodge) they haven't kept the sill tight to the frame hence the gap. You might not be able to push the sill up as the screw threads will stop it.

 

Did they use expanding tape or foam around the top and sides? Or is the foam packed you refer to pushed in foam?

 

@craig?

 

 

Edited November 27, 2021 by Onoff

[Mr Punter]

It looks like rain could easily find its way in, especially if it is blown by wind.  Once it is in there it will be trapped.  Also cold air can circulate around the frame.

[Onoff]

The sill detail is likely something like this:

 

 

 

[ST1978]

2 hours ago, Onoff said:

Sorry, bodgers. In and out, quick as.

 

Imo bits of paper and certs can mean very little. Easy to buy into a club.

 

A big problem is that as they've put a screw in from the top (again a bodge) they haven't kept the sill tight to the frame hence the gap. You might not be able to push the sill up as the screw threads will stop it.

 

Did they use expanding tape or foam around the top and sides? Or is the foam packed you refer to pushed in foam?

 

@craig?

 

 

Cheers for the response. They've used expanding foam round the top and sides, and in a couple of cases at the bottom too! I challenged them on the foam under the sill and they said they were going to scrape it out and push mortar in the gap. 

 

They've also done the sliding patio door in a similar way. The sill has definitely not been bedded on fresh mortar. The sill has similar gaps as above and so the door cannot be securely sitting on it. It's a bit of a mess.

[ST1978]

1 hour ago, Mr Punter said:

It looks like rain could easily find its way in, especially if it is blown by wind.  Once it is in there it will be trapped.  Also cold air can circulate around the frame.

 Exactly...in fact it has just rained and snowed here and you can see how easily moisture gets into the gap. The thing is, it can run along the top of the sill and because the ends aren't sealed to the window, it'll just run off and land on expanded foam, or brick, or find its way into the cavity. 

[ST1978]

1 hour ago, Onoff said:

The sill detail is likely something like this:

 

 

 

It's virtually the same as this photo. Screwing up from underneath into the frame is clearly the way it's intended to be done. Water can run along the top face of the sill, so there needs to be good sealing between the 2 things if I understand it correctly. I've read a few fitting guides from different manufacturers and they all mention this step. 

 

Should they first offer up, cut and level the sill with packers. Then remove the sill, and apply silicone or mortar to the top of the wall. Then fix and seal the sill to the window frame, then sit the whole lot onto the silicone/mortar? 

 

Is this something that can be recovered without the windows coming out? 

[Mr Punter]

The simplest thing to do would be to make sure it is all clean and dry, gun in a load of silicone and leave a neatly tooled finish.

[saveasteading]

4 minutes ago, Mr Punter said:

gun in a load of silicone

Simplest yes, but not the long term solution.

Silicon degenerates and goes hard. Then you will have to scrape it out and replace it.

The boss of a good window company will despair at this (and be glad you told them), and get it remade at their own expense.

[craig]

Thanks @Onoff replied via PM he sent but without seeing/knowing all the facts it’s difficult to be critical. I don’t like being critical of others installs unless absolutely necessary or I’ve been called in as an independent “expert” i use the term loosely as I’m still learning the trade every day.

 

However, saying that. There is certainly issues which shouldn’t have occurred. Packers should remain in place as it keeps the frame square. Think heel and toe of glass, frames are the same.

 

From what you can see in pictures, the honest answer is I’d kick my guys in the nuts, apologise to the client and tell them to get it sorted (properly).

Edited November 27, 2021 by craig

[Mr Punter]

6 minutes ago, saveasteading said:

Simplest yes, but not the long term solution.

Silicon degenerates and goes hard. Then you will have to scrape it out and replace it.

The boss of a good window company will despair at this (and be glad you told them), and get it remade at their own expense.

 

Yes, windows out and sills and windows fitted as per manufacturers instructions is best but I thought the OP did not want the windows to be removed.

 

They should have screwed the sills in first.  Like a scene from White Gold!

[ST1978]

I've spotted a pile of issues with the patio doors this afternoon too. The bottom of the bottom or top of the frame aren't fixed into the brickwork, the sill is wobbly with gaps as per the windows, the frame sits forward on the sill so the upstand is 7-8mm back, no sealant used again between the sill and frame, but it doesn't sit on the sill properly anyway. It's well screwed at the sides, but there are no packers in place which I guess there should be.

 

If they need to come out to correct the job then they need to come out. The fitters (2 brothers) aren't going to accept this easily though and are defending their work saying they've never had any complaints before. To be fair, once trimmed up the windows look tidy. It's only when you start to poke, wobble and look closely...especially at the partially finished windows, that the problems start to reveal themselves.

 

Cheers for all your comments. Any advice on finding an independent assessor to take a look?

 

Stew

EU00370_Is1_Syncro Installation Guide_Web_Mar20 (2).pdf Logik Windows Installation Guide Feb 21 (2).pdf

[craig]

I’ll reply here rather than PM. 
 

Unfortunately I don’t have anyone local to you and I’m not planning to be in the area until January at the earliest.

 

Install guide is clear on the fixing of sills. Yes it’s a pain the **** to fit the windows once they are fixed but it’s how they should be fitted and what they’re getting paid to do.

 

If they wan’t paid the remaining amount and they will. They’ll put it right, maybe with gritted teeth but they will.

 

 

[Marvin]

8 hours ago, Onoff said:

The sill detail is likely something like this:

 

 

 

With that I usually run silicone along where the 2 parts touch and screw up in the cill recess.

 

On mine I filled the cill under the window with insulation....

[Onoff]

47 minutes ago, Marvin said:

On mine I filled the cill under the window with insulation....

 

Me too. I clamped timber either side and used low expansion foam. Worked a treat and no distortion.