Window sill heights for toughened glass new build?

Ruggers · 6 Sep 2020

In a new build, how high do the window sills need to be from the finished floor level to avoid needing toughened or laminated glass?

Where is the measurement taken from, is it from the finished concrete floor height or weyrock board to the top of the window sill, the actual glass in the frame or something else?

frutbunn · 6 Sep 2020

Ruggers said:
In a new build, how high do the window sills need to be from the finished floor level to avoid needing toughened or laminated glass?

Where is the measurement taken from, is it from the finished concrete floor height or weyrock board to the top of the window sill, the actual glass in the frame or something else?

800mm from the finished floor level where the glazing is exposed, unless in or within 300mm of a door then its 1500mm

Ruggers · 6 Sep 2020

So it's from the finished floor height to the actual glass, not the window sill? Looking at my own windows the glazing sits 120mm higher than the inside window sill. I have 120mm of frame & sash.

frutbunn · 6 Sep 2020

Ruggers said:
So it's from the finished floor height to the actual glass, not the window sill? Looking at my own windows the glazing sits 120mm higher than the inside window sill. I have 120mm of frame & sash.

Thats correct

Ruggers · 6 Sep 2020

Do you know what the maximum window sill height is. I keep reading 1100mm max which is mainly for bathrooms and kitchens, but it doesn't say if it's 1100mm to the lowest part of the opening or whether it means to the top of the inside sill.

To keep inline with brick courses the window opening was going to be 975 or 1050mm. 975mm isn't high enough for the kitchen because the UFH screen will be around 60mm thick, then 910-930mm finished worktop height.

1050mm window size height seems best, and 1050mm of the floor which comes inline with the 2100 lintel heights of the doors.

DevilDamo · 6 Sep 2020

Maximum height in terms of what... fittings/worktops or BR’s?

Using a nominal 2.1m from external DPC to window/door heads, then it’s common to have 1050mm deep windows to Kitchens/Bathrooms, etc... and 1200mm deep windows elsewhere.

frutbunn · 6 Sep 2020

Ruggers said:
Do you know what the maximum window sill height is. I keep reading 1100mm max which is mainly for bathrooms and kitchens, but it doesn't say if it's 1100mm to the lowest part of the opening or whether it means to the top of the inside sill.

To keep inline with brick courses the window opening was going to be 975 or 1050mm. 975mm isn't high enough for the kitchen because the UFH screen will be around 60mm thick, then 910-930mm finished worktop height.

1050mm window size height seems best, and 1050mm of the floor which comes inline with the 2100 lintel heights of the doors.

There is maximum height of 1100mm to escape windows under B regs, but this only relates to the escape window opening, not cill heights

Ruggers · 6 Sep 2020

DevilDamo said:
Maximum height in terms of what... fittings/worktops or BR’s?

Using a nominal 2.1m from external DPC to window/door heads, then it’s common to have 1050mm deep windows to Kitchens/Bathrooms, etc... and 1200mm deep windows elsewhere.

I've seen a few times mentioning theres a maximum height of 1100mm for the lowest part of a window, don't know if this is for the lowest part of the brickwork window opening, or if it means to the actual upvc sash opening lowest point for escape regs?

1200 deep would mean an internal sill height of 900mm, that seems very high for what i'm used to in a living room or bedroom, the glazing would be over 1m

frutbunn · 6 Sep 2020

Ruggers said:
I've seen a few times mentioning theres a maximum height of 1100mm for the lowest part of a window, don't know if this is for the lowest part of the brickwork window opening, or if it means to the actual upvc sash opening lowest point for escape regs?

1200 deep would mean an internal sill height of 900mm, that seems very high for what i'm used to in a living room or bedroom, the glazing would be over 1m

This is to the lower part of the opening and only to windows used for escape and does not relate to the cill

^woody^ · 6 Sep 2020

Has uni started already?

DevilDamo · 6 Sep 2020

Ruggers said:
1200 deep would mean an internal sill height of 900mm, that seems very high for what i'm used to in a living room or bedroom, the glazing would be over 1m

Well lower the cill then and have more glazing

Bear in mind you start getting to near to the ‘critical locations’ regulations.

Ruggers · 6 Sep 2020

frutbunn said:
This is to the lower part of the opening and only to windows used for escape and does not relate to the cill

Are all windows classed as escape windows if they are the only window in the room?

^woody^ said:
Has uni started already?

Is this short for something or sarcasm?

DevilDamo said:
Well lower the cill then and have more glazing Bear in mind you start getting to near to the ‘critical locations’ regulations.

What are critical locations? An architect suggested 1350mm deep window openings.

frutbunn · 6 Sep 2020

Ruggers said:
Are all windows classed as escape windows if they are the only window in the room?

This would depend on a number of factors, but as a very general rule above ground level to habitable rooms unless there is a protected stair or to inner rooms on the ground floor.

Ruggers said:
What are critical locations? An architect suggested 1350mm deep window openings.

The critical locations are in the diagram I've previously posted. No idea where he's got 1350mm though.

Ruggers · 6 Sep 2020

1350 was just the size an architect suggested instead of a 1200 high window.
1800 wide x 1350mm height of the window opening with cill height just over 800 internally.

DevilDamo · 6 Sep 2020

You have mentioned ‘an architect’ a couple of times now and the questions you are asking are those an architect should know. What are you actually trying to find out or achieve?

Btw, you are aware the sizes the architect has mentioned are basically ‘structural‘ opening sizes including the frames so therefore not the size of your actual glazed area?

Having a read of the BR’s in particular ADB and ADK will answer most of your questions.

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Window sill heights for toughened glass new build?

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