Here is the original elevation, showing the windows 800 mm from internal floor height...

1100mm above floor height might be ok for a bedroom or bathroom, due to privacy concerns, but is way too high for a living room. Why are the tops of the windows so far below the eaves? Are you trying to reduce the amount of light entering to prevent overheating?

In my old Victorian house, the cills are between 24" and 26" from the finished floor (600 - 650 mm) - though the kitchen one could do to be a bit higher (more like 800mm).

There's nothing worse than cills that are too high so that you can't see anything if you're sitting in your living room!

Paul in Montreal.

1100 is for people who like to feel safely tucked-up indoors and/or protected from risk of being seen from outside - favoured by spec builders presumably because that's how middle-England feels. Personally I, and luckily my clients, want to lower cills, even to window-seat height. That's not to say picture-windows, super-wide or down to floor - fish-bowl is not nice.

Why not raise the heads, leave cills where they are?

There is a minimum height required by building control on upper floors I believe (although I'm afraid I can't tell you what it is). On my new build our windows are lower than the minimum as they need to line up with next door for aesthetic reasons so we have had to fit opening restrictors to prevent the risk of falling out. Not a huge issue, but a small expense that could be avoided.

Posted By: Peter_in_Hungaryraising the heads could be expensive and involve all sorts of structural changes

AIUI this is a new-build, yet to happen?

Our window sills are about 1000 mm (probably 40 inches) above floor level, except for the living room one which is only about 300 mm to give a good view. They extend to about 200 mm below the ceiling, so upstairs quite close to the eaves. I think the issue you have is that the windows are on the small side, so that if placed at a 'normal' height above the floor appear too far below the eaves.

Ed

1100 is also the maximum height for an escape window (at least in Scotland, I assume it's the same in England, etc).

<blockquote><cite>Posted By: cjard</cite>800mm is the minimum height to not require toughend/laminated glass. 1100 is the height that a barrier must be to provide adequate protection from accidental falling. </blockquote>

I thought 800 was also the min height for fall protection. Google found..

https://www.fdean.gov.uk/media/Assets/Planning-BC/documents/approved%20documents/Replacement_of_External_Windows__Doors_spec_Sept_2010.pdf

"K2 - Protection from falling Where a first floor window sill height is less than 800mm above the floor level suitable guarding should be provided to prevent a person falling through an open window. This requirement may conflict with Regulation B1 and provision of escape windows. One way of achieving the requirement may be to provide a restricted opening device that can be easily overridden in the event of an emergency."

For a new build, I would set the window sill height with respect to what furniture is likely to be placed there. You don't want a low sill and then place a sideboard across the window or a dressing table. If the wall is likely to be blank between the windows (perhaps a small table between them), so the view of the garden is paramount, it is still instructive to see what you would see through the lower bit of the window - bit of patio? Unless you are on your hands and knees.
Frank

Sorry, I glossed over a detail again..

900mm for domestic stairs and other things that prevent a fall internally
1100 for domestic juliette balconies and other things that prevent a fall externally

The height of the lowest visible/touchable bit of glass..

Thanks, that's what I thought and is good news!

Posted By: ComeOnPilgrimThe sills are currently 800 mm from the internal floor.

If you want to put a bed under it, how tall is the headboard. Alternatively any furiture under the window (if you own it) chek it fits (and yes I have that Tshirt).