Question Regarding Roof Beams (1950s Chalet Bungalow)

[Axe]

Hello

I have a 1950s chalet bungalow which has a simple roof construction comprising only rafters, with no other inner structural members apart from one horizontal beam each side, set into the gable ends and running the full length of the roof space.

These two beams (one each side) are positioned - unsurprisingly - half-way between the ridge board and the tops of the downstairs walls, to brace the rafters at their mid points.

It's similar to the photograph at the bottom of this page (please ignore the RSJs etc; I'm just referring to the horizontal beam near the top of the photograph):

http://www.loft-conversion-cost.co.uk/designing.html

In my case these beams effectively dictate the width of the roof bedroom as the bedroom's stud walls are positioned immediately inside these beams.

The beams don't appear to be under a great load as I can move them very slightly if I push hard against them.

If I wanted to add a dormer window, or widen the room, these beams would be in the way, so is it possible in principle to remove a section of these beams (for example, to install a dormer window), by fitting vertical struts that transfer the load from the beam's cut ends, down to the floor joists immediately below?

Or for room-widening, could these beams be removed completely by substituting their presence with vertical struts from each rafter, down to each corresponding floor joist below?

The floor joists for the roof bedroom are 6" x 2", if that is significant.

Thanks very much

 

[freddiemercurystwin]

No you can't just cut them and transfer the loads down to the ceiling joists. This work is notifiable and should be done under Building Control's eyes and as a such they will expect a structural engineers input.

 

[Axe]

Thanks for your reply

I wonder how people fit dormer windows to these types of roofs. The beam is well and truly in the way for things like that.

 

[Static]

You either support the cut purlin on a load bearing stud wall which then is supported on a new steel at ceiling level (which you will probably need anyways for the new floor joists)
Or you mess about with adding steel or timber rafter beams but this ends up messy and alot hard to get in without destroying the roof..

If you are considering converting your loft, go find a half decent architect/technician that does this kinda thing all the time and can sort any building regs/planning issues.. draw up some plans.. get an SE to design something to keep your roof ontop of your house and not in the lounge.. then find a builder who wont charge you a 3rd mortgages worth of extras..

 

[Axe]

Okay, all noted, thanks.

The room actually exists now and is part of the original house design (dormer bungalow upstairs bedroom). The purlins are hidden from view in the front bedroom due to the stud walls being installed just inside them, so they're only visible from the 'outboard' loft space.

It looks as if it's going to be a floor-up job then, if I have a dormer window installed.

There is a rear bedroom that was converted from loft space in the 1970s where some fool laid the floor straight onto the original 4" x 2" joists (thinner joists than used in the front bedroom as the rear was only designed to be used as loft space). That's another story though as I know that floor needs to come up and have at least 6" x 2" to match the front bedroom.

Oh well, maybe I could have Velux windows instead, and avoid the purlins altogether.