Garage roof ideas

[oldbutnotdead]

Morning all,
Anyone got any interesting roof designs for this here structure (plans attached). Given the span, I'm looking at Glulam or similar beams, BCO has suggested trusses (which I don't want cos I'll lose all the headroom) or if I want to use rafters he wants structural calcs.

Has anyone else had this with Glulam or anyone got any other thoughts (including how cost-effective would steel purlins/struts be?)

Cheers

Sections from all planes

• oldbutnotdead
• 8 Dec 2014
• 3

Plan masked

• oldbutnotdead
• 8 Dec 2014
• 3

PS If plans are too small, width is 6800 with clear span of 6600 at 10 degree pitch (so about 6700 ish). Length of garage is 9400 to outside. Another vote against trusses- they'll get in the way of the roller shutter housing.

 

[freddiemercurystwin]

Just use traditional rafters, you will fall off your chair if you get a price for glulams (and these would need calcs anyway, normally done by the supplier) and in anycase are unsuitable here.

Traditional rafter sizes are actually in the Building Regs (albeit a very old version of Part A), your BCO is an arse for expecting you to provide SE calcs for them (maybe he's wet behind the ears) anyway something like 50x195 @450 centres would be OK and if he insists on SE calcs they should be no more than about £60 if you find the right SE.

Any exploration into purlins or steels will require SE involvement and IMHO is unnecessary anyway.

 

[oldbutnotdead]

Ta- been hunting around again and found a freebie set of TRADA tables (from Chichester University)- trouble is their span maxes out at 6.5 (which may be why BCO is wanting big boy sums for rafters). He's (BCO) been very sensible and helpful about other stuff and def not new to the game (I've known him for 15 years in a previous existence) so tending to take him seriously.

I've priced Glulam (or some sort of manufactured beam thing anyway)- it was chunky but not crippling (about £30 each)- also priced solid rafters to the span and that was getting into some very heavy and very pricey bits of rainforest! (couple of 8 x 3 I needed in the house came to about £40 each for 4800).
Where the Glulam starts smarting is at 400 centres on 9400 = 24 of the things..... but my suspicion is that metalwork would probably cost the same or more, hoping to get some pros and cons from here (I prefer timber but if metalwork was half the price then that'd be a chunky saving)

 

[freddiemercurystwin]

Ahh Nooooo!!! I just re-read your drawing and for some reason when I first glanced at it I thought the 4500 dimension was the span, so ignore my post it is officially useless and remove the pointless thanks too while you’re at it!

So, ahem, moving on, yes you are right the span tables will not help you here hence BC insistence on SE calcs.

So glulams for this span may well become viable afterall but otherwise you are probably looking at either one or two steel purlins (spanning the shortest distance) and then timber rafters on top (or between the webs), in which case you are looking at SE involvement anyway. Prolly something like a 254x89 or maybe smaller. If you span lengthways the beam would be colossal and also would obviously need to bear onto your lintel which is obviously even more costly/complicated. Your SE may need to design some angled plates on the underside of the beam(s) at the bearings to prevent the beam from wanting to slide down the slope if you get my gist.

Incidentally why have you got such a big slope? And also the gap between the top left hand corner of the door and the roof looks quite narrow will may leave it prone to cracking.

 

[oldbutnotdead]

Heh- oops and all that, glad it wasn't me missing something obvious (tho wouldn't be a first for me).

Sounds to me like the beams are the simpler way to go- baffles me why I need so many of them to support tin sheets but there we go. Steel beams that sort of size sound as if they'd need craning in which would kick the budget in the teeth straight away.

Slope isn't that big- only 10 degrees- and fingers crossed on the cracking bit above the lefthand side of the door. The front wall there is double thickness so that should help. Think the guy who drew the thing up was concerned about snow loading at any shallower pitch

And I'll not unthank you- that would be rude!

 

[freddiemercurystwin]

Yes rooves have a design load of a (once every hundred years maybe) snow load of 1m depth as well as the expectation that a couple of burly builders could be up there re-doing the roof.