Green Building Forum - Window sill height from floor?

Window sill height from floor?

ComeOnPilgrim — Mon, 18 Jan 2016 14:09:00 +0000

Hello GBF. We are revising our external elevations. At present the windows look to be too low as there is big 'gap' between the windows and the eaves. The sills are currently 800 mm from the internal floor. One is a main bedroom, one is a living room, and one is a bathroom. We'd like to increase their height to, say, 1100 from the internal floor. Does anybody have any ideas / recommendations for appropriate distances, and whether this is too much?

I'd be grateful for any comments!

Window sill height from floor?

ComeOnPilgrim — Mon, 18 Jan 2016 14:12:07 +0000

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

Window sill height from floor?

ComeOnPilgrim — Mon, 18 Jan 2016 14:12:50 +0000

And here is a SketchUp file showing the windows moved up slightly, so they are 1100 mm from internal floor height.

Window sill height from floor?

Paul in Montreal — Mon, 18 Jan 2016 14:23:59 +0000

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.

Window sill height from floor?

DarylP — Mon, 18 Jan 2016 14:25:42 +0000

.... do they have to comply with B. Regs, Personal Means of Escape max height of cill from ffl?

Window sill height from floor?

fostertom — Mon, 18 Jan 2016 14:29:04 +0000

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?

Window sill height from floor?

Peter_in_Hungary — Mon, 18 Jan 2016 14:52:49 +0000

Raising the cills is easy, raising the heads could be expensive and involve all sorts of structural changes - depending upon where the structural support beam is above the window. Frequently the beam or arch (depending on the age of the house) is just above the window so any changes here involve structural changes.

If you raise the cills have a regard to the minimum window size (and opening light) required by the regs,

Personally I agree with FTom about the height of cills

Window sill height from floor?

richardelliot — Mon, 18 Jan 2016 14:56:45 +0000

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.

Window sill height from floor?

ComeOnPilgrim — Mon, 18 Jan 2016 15:44:15 +0000

Thanks everyone!

The living room is both windows on the ground floor. The LHS window is very large, and will have a low sill so it will be possible to see the garden. In some ways we thought it might be preferable to also have part of the sitting room that is a little more private.

Raising the heads is an option, but we'd quite like to preserve both the 'punched hole' and square impression of the windows in the rendered part.

Window sill height from floor?

fostertom — Mon, 18 Jan 2016 16:29:56 +0000

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?

Window sill height from floor?

ComeOnPilgrim — Mon, 18 Jan 2016 17:07:28 +0000

@fostertom, yes, this is a new build. Hempcrete, so changing the windows should not involve structural changes. That said, we dont' plan on changing the windows once they're in!

Window sill height from floor?

atomicbisf — Mon, 18 Jan 2016 19:57:57 +0000

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

Window sill height from floor?

cjard — Mon, 18 Jan 2016 21:53:41 +0000

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. To be able to fall, there must be a height differential of 600mm between floors either side of the barrier

Window sill height from floor?

Ed Davies — Tue, 19 Jan 2016 10:16:37 +0000

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

Window sill height from floor?

djh — Tue, 19 Jan 2016 13:53:30 +0000

The main concern as regards the height of the heads of the windows for me was that I must be able to see out of the window whilst standing up!

Window sill height from floor?

CWatters — Tue, 19 Jan 2016 20:39:44 +0000

Posted By: cjard800mm 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.

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."

Window sill height from floor?

cjard — Wed, 20 Jan 2016 21:53:51 +0000

Yes, sorry I should have expanded:

800 is the minimum height for standard glazing. If a window sill is lower the window must be toughened or laminated
800 mm is the minimum height of a sill to prevent failing out of a window. Sills below this level would need additional measures such as opening restrictions, barriers etc if the fall out of the window, to the ground was greater than 600mm
1100 mm is the minimum height of a balustrade at stairs, juliette balconies etc

Window sill height from floor?

chuckey — Thu, 21 Jan 2016 08:35:44 +0000

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

Window sill height from floor?

djh — Thu, 21 Jan 2016 11:40:55 +0000

Posted By: cjard1100 mm is the minimum height of a balustrade at stairs, juliette balconies etc

I think that's for commercial stairs. Domestic ones, it's 900 mm I believe.

Window sill height from floor?

cjard — Fri, 22 Jan 2016 07:03:20 +0000

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

Window sill height from floor?

djh — Fri, 22 Jan 2016 09:26:46 +0000

Does the 800 mm min height for toughened glazing refer to the height of the sill, or the height of the glazing?

Window sill height from floor?

cjard — Fri, 22 Jan 2016 19:44:55 +0000

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

Window sill height from floor?

fostertom — Fri, 22 Jan 2016 21:12:28 +0000

The 'sight line', they call it

Window sill height from floor?

djh — Fri, 22 Jan 2016 21:45:32 +0000

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

Window sill height from floor?

Forester — Fri, 06 May 2016 13:02:40 +0100

Hi cjard, I came across this thread while planning the windows for our loft conversion - all really helpful. I've been looking on the Planning Portal website for 'official' confirmation of these regulations for window height and no joy - is there any chance you can point me in the right direction? Thanks very much in advance!

Window sill height from floor?

borpin — Sat, 07 May 2016 21:11:11 +0100

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).

Window sill height from floor?

Ed Davies — Sun, 08 May 2016 10:46:20 +0100

Forester,

If you're in England or Wales you need the appropriate Approved Documents:

https://www.planningportal.co.uk/info/200135/approved_documents

Parts B and K will likely contain the various rules. Haven't looked at them for a few years so wouldn't be sure on that - maybe there's something in one of the other parts that's relevant.

In Scotland it's the Domestic Handbook 2015 which contains the definitive rules:

http://www.gov.scot/Topics/Built-Environment/Building/Building-standards/publications/pubtech

Not sure about NI.