Roof window on an upstand to avoid cutting roof trusses

[IanMc]

Hello - I wonder of anyone could offer some advice on this or an alternative approach.   I like to get more natural light and ventilation into a north facing bedroom.  It only has one external wall with no scope to extend the current small window in it.  It's a bungalow with a shallow (17 degree) slope concrete tiled roof.  The most obvious way to go seems to be a roof window, but the roof trusses are pre-fabricated items at ~17" centres.   I want to avoid cutting the trusses as I would have to essentially build a new section of roof for the window to sit in.  400mm wide roof windows don't seem to exist (I could have two side by side - or is there a custom builder out there?), so I was thinking I could get a wider top opener and fit it on a short upstand and centred across two trusses so you can still get at the handle easily.  I can live with tidied up exposed trusses inside and it does not need to be a means of escape.  Thinking it through, I get a bit stuck at the flashing stage, as I assume I will end up with a gap or very small overlap along the edge of the window between the flashing and the window trim.  I suppose I could just bridge it with a flashband or custom trim...but feels a bit messy.   Or I forget the factory flashing kit and make my own, but I am not sure where to start with that.

 

Any advice gratefully received!

 

Thanks, Ian

 

[nod]

The 17 degree isn’t an issue as you can buy a roof light window that will do a shallow slope 

Pics would help 

When you say trusses Are you converting the loft ?

[PeterW]

You can get custom fixed roof lights to any size - Roof Maker do them for example. 
 

Cutting and retrimming to standard sizes isn’t that onerous as long as you do it properly and also only remove one truss of a set  - any more than that and you need to look carefully at the top chords and beefing up the framework. 

[IanMc]

HI - thanks for the responses.  I am not converting to a loft - it's a bungalow with a shallow roof pitch.  I intend to put a roof window in and trim out so it connects directly to the bedroom below.  A light tunnel of about 203'.  I did investigate adding a floor, but that got out of hand really quickly - this is a compromise on that.

 

I'll look at roof maker - thanks for that.

 

I perhaps haven't used the right term for the trusses.  Having just googled what I have, it is a "cantilever" design. ie. a large triangle with two Vs coming down from the apex.  I've been told no structural engineer will sign-off on cutting them.  You essentially have to insert full loft style trusses around them (double either side) and build the roof window into them.  Not an impossibly large job, but disproportionate to me just looking for more light and ventilation in the bedroom!

 

PeterW - your comment about removing one  truss still stands given what I have just described?  If so great, I can live with a window of that width.  I was told no cutting whatsoever by an architectural consultant.

 

The problem I can see with most roof light installations is they assume you are cutting the rafters and the window is recessed.  A top opener on an upstand is my compromise.

 

I'm not at home for a few days, but I will take a few pics and post.

 

Thanks again.

[ProDave]

So the window is going to be some way above the ceiling of the room (203 feet? Not sure what 203' is meant to mean) and you are going to make a light tunnel to bring light into the flat ceiling of the room below?

 

If that is your objective, I would look instead at the product designed to to that, a light pipe. They go under various trade names like solar tube etc.

[Temp]

Normally you support and then cut out a section of one rafter. Then fit doublers around the opening. Not sure if can do this with trusses. Might need input from an SE.

[IanMc]

 

23 hours ago, ProDave said:

So the window is going to be some way above the ceiling of the room (203 feet? Not sure what 203' is meant to mean) and you are going to make a light tunnel to bring light into the flat ceiling of the room below?

 

If that is your objective, I would look instead at the product designed to to that, a light pipe. They go under various trade names like solar tube etc.

 

That's right - I meant 2-3 feet (slip of the keyboard).   The only problem with light tubes is they are non-ventilated as far as I can see.  The room gets very stuffy as the existing window open out into an area that is enclosed most of the time (always at night).

 

22 hours ago, Temp said:

Normally you support and then cut out a section of one rafter. Then fit doublers around the opening. Not sure if can do this with trusses. Might need input from an SE.

 

Yes, I think that is for full size rafters not cantilever trusses.  I think it is worthwhile double checking with an SE direct as I got his second hand.

 

Thanks again!