Minimum window dimensions
Discussion
Am starting to think about what windows to order for the front of our house, the openings are not very large 1100mm wide x 1070mm high. Can anyone tell me what the minimum size openings I have to comply with regarding upstairs rooms. All I can find online is a dimension of "no smaller than 450x450mm". And if below 800mm from floor needs to be toughened glass. Windows will be PVC I don't like plain all openable windows would like to split the dimension into 3 with a full half opening and the remaining half with a small opening top part but think this will be under the 450x450 rule. The windows at the minute do not comply with this rule but are 30 years old and hardwood but are falling apart. (Going PVC as I can't be arsed with the maintenance of wooden windows)
If they haven't changed recently, that won't comply. We had a similar issue a few years back, when we had the Windows designed, they were made to look like the rest of the windows, although they ended up with essentially a false middle frame as part of one side. When opened they went left and right, giving the 800mm or so in the middle to meet building regs for getting out in event of fire.
Means of escape
When replacing any window, the opening should be sized to provide at least the same potential for escape as the window it replaces. If the original window that is being replaced was larger than necessary for the purpose of escape, then the new window opening could be reduced down to the minimum as specified in the criteria below.
The means of escape should be considered for any new window installed to an extension or existing dwelling. If an escape window is required then criteria set out below should be followed. It is also generally good practice to replace any window on the first floor that is not used as an escape window with an escape window.
See below for the general criteria for egress windows:
Width and Height - Either of these are not to be any less than 450mm
Clear Openable Area - No less than 0.33m²
Cill height - No less than 800mm and no more than 1100mm from floor level.
Only one window per room is generally required.
When replacing any window, the opening should be sized to provide at least the same potential for escape as the window it replaces. If the original window that is being replaced was larger than necessary for the purpose of escape, then the new window opening could be reduced down to the minimum as specified in the criteria below.
The means of escape should be considered for any new window installed to an extension or existing dwelling. If an escape window is required then criteria set out below should be followed. It is also generally good practice to replace any window on the first floor that is not used as an escape window with an escape window.
See below for the general criteria for egress windows:
Width and Height - Either of these are not to be any less than 450mm
Clear Openable Area - No less than 0.33m²
Cill height - No less than 800mm and no more than 1100mm from floor level.
Only one window per room is generally required.
The general rule was you can't make it worse than the window you replace in respect of opening size. So if you are replacing box sash windows that have large openings then you have to keep large openings, if your replacing a casement window with a small top opener then you can keep the same style. Obviously its good practise to have windows that you can escape from in the event of fire though.
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