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Upvc windows don't seem to fit

I have just had new upvc windows fitted by a reputable FENSA registered company. Now that the damage to the plaster around the windows has been made good I realise that the window frames are a bit odd compared to my other window frames (also new upvc): internally they seem to have fitted all the frames within another frame so that where you'd expect the window frame to meet the plaster it doesn't and seems to have had an extra section added on to bridge the gap between the new frame and the actual window aperture. On one of the windows this little add on seems to have slipped and there is a gap which opens to the outside between the window frame proper and this funny outer frame.
The company have told me that these add ons are "adaptors". I cannot find any mention of such things on any web sites and was not warned that my windows would need these things which in my opinion seem to defeat the insulating properties of the sealed window frame.
I think that something has gone wrong with the manufacture of the windows and they have been made too small (measurements don't seem to correspond to the ones on my survey quote) and they are attempting to fob me off.
Has anyone else ever heard of the need for adaptors to make their windows fit?
Added detail: to clarify these add ons are visible inside and they are not there to conceal decorative damage. Also I have now measured the frame sizes and they do not corespond to the measurements on our survey quote!

5 Answers from MyBuilder Window & Door Fitters

Best Answer

Sorry to say that it does sound like a problem has happened from the initial survey to the making of your windows, add-ons are used when you need to reduce the size of a window to reduce the opening size if its touching somewhere for instance if there are stone mouldings outside etc, if there is nothing in the way than sorry to say it sounds like they were made wrong, a picture would help me confirm this.


Answered 5th Oct 2015

Hi, addons are used to make the frame a little smaller but still get it to where it needs to be. For example if the internal measurements are alot smaller than external measurements there used so the frame is not all sat behind the plaster. Addons are also used to stop openers, doors ect catching. However when i use a addon i always make sure they are not visible by triming and sealing them. Hope this helps.


Answered 9th Apr 2017

Hi there could you post a photo ,
I've only quickly read your question as I'm going on a emergency call.

Sometimes there is a need for 'add on' to the upvc window, this is usaully added if for example the inside reveal is smaller than the outside . So the window can open and is central etc

Hope this is sort of helpful


Answered 5th Dec 2014

Add on's genuinely are used on top of upstairs window frames to reduce the frame if there is a low soffit on the outside. This helps for the opener to pass clearly under it and gives a full opening. Or if there is a majority difference between the reveal size on the inside and the actual brick, they will then be used so that not all of the frame disappears behind the inside plaster. Good examples of these are in bathrooms if the reveals have been tiled ontop of plasterboard.


Answered 3rd Mar 2019

The sizes on quote are a rough measurement to give a price frame add ons are perfectly fine if they are put onto the frame correctly


Answered 5th Jun 2019

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