Advice on foreign roof quality please

[anonymouscoward]

Hi,
I'm a Brit but living abroad (Belgium), and currently having a fairly major refit done on a house. Our Belgian builder has put up a new extension with a timber frame flat roof (about 5m deep by 7m wide). The frame has a large beam running front to back, off-centre, with about 4.5m on on side and about 2.5m on the other. There are spars going at right angles from the walls to this central beam (which is two beams side by side).

There are no noggins at all between the spars, and the builder claims they're not necessary. Also, the firrings (apologies if I get the words wrong) are planks nailed to one side of the spars, going across the roof, rather than wedges going front to back. I guess this would also make the placing of noggins difficult now that the firrings are in.

Is the lack of noggins and the style of firrings normal? Would this be a standard approach to make a flat roof in the UK? We're getting into a bit of a discussion with him about whether the noggins are needed, and would appreciate some disinterested expert opinion...

Thanks,

Tom.

 

[nortonj]

A few pics would help

 

[anonymouscoward]

 

[anonymouscoward]

Hi, sorry about forgetting the pics :-/ Voila, les magnifik photos!

Any comment appreciated, esp. from a noggin expert.

Looking at the photos I think I got the division of widths wrong - the vertical steel pole is in the middle of the span at 3.5m, so the wooden beam in the middle isn't far off that.

Also, there will be a roof terrace on top of the half where there isn't the light well - i.e. on top of the half with the longer spars to the middle beam.

Merci,

Tom.

 

[nortonj]

I'm a plumber so no expert, hopefully a roofer builder will comment. Doesn't look quite right though. And why do you have a support at the centre of the rsj? Is the beam itself not big enough? Did you have any calcs done by a structural engineer?
hope you get it sorted.

 

[catlad]

I am struggling to see how you can have a roof terrace with those
timbers attached to the side of the beams acting as timber firings.
And if he is not going to have noggins how will he attach the plasterboard?
There are many different ways to construct things but it does look odd
without knowing what his plan is overall.

 

[ajstoneservices]

You're in Belgium and want Brits to advise you on Belgium building methods. No wonder expats get a bad name.

 

[anonymouscoward]

Hi,
The rsj has another two storeys on top, the column was recommended by an engineer.

Yes, i realise that the methods might be a bit different in Belgium, but I thought that flat roofs are probably pretty similar everywhere. You know, beams, firrings, etc... made out of the same stuff, same rules of gravity Hence asking whether this would be considered ok in the UK, as a sort of double check.

Tom.

 

[anonymouscoward]

Hi again,
Talking of plans, the original plan was to have the beam across the middle of the roof in steel and resting on the brickwork, and the beam across the top of the sliding window (the big gap) also in steel. These got changed for wooden beams without asking us, and now the beam supporting the middle of the roof is mounted on the beam across the top of the sliding window instead of on the bricks.

Isn't there some risk that the beam across the window is going to sag?

Tom.

 

[anonymouscoward]

PS thanks for the replies. I'll try to get the firings checked whilst I'm at it.

 

[Deleted member 174758]

My experience is that you normally don't put noggins into a roof unless there is the need to have extra rigidity and to support extra weight (such as you'd have with a roof top patio). In any case sheet material such as plywood or OSB fixed through the top of the firrings into the spars should add a degree of rigidity. Using a doubled-up trimmer to carry the rafters may be a way to reduce the cross section of the rafters due to the reduction in span. Can't say I like the idea of "firrings" done that way - I'd be suspicious that the roof may sag in places over time. The way to have avoided that would have been to orientate the spars at 90 degrees to their present orientation - but doing that would put a lot more loading onto the RSJ (which would have to be much larger as a consequence and may also have required extra depth/strength of masonry in the support piers). I think that you may have a compromise forced by the position and size of that RSJ. Any idea what the S/E said about this? Overall the carpentry work looks neat, but unless I'm mistaken the builder hasn't filled all the holes in the truss hangers with nails - it's pretty much the norm that ALL the holes need to be nailed with twist nails and that standard applies in The USA as well as the UK (and was also becoming the norm 30 years back when I had a house in the Netherlands)