New garage roof large span

[BotusBuild]

The new garage being built with ICF walls has an internal floor dimensions of about 5m x 6m, with the single pitch (flattish) roof sloping from one 6m side to the other.

My current plan is to put in a central 5.5m(ish) beam with joists at right angles (~3m each).

Q. Glulam or steel for the central 5.5m beam?

[Mr Punter]

Glulam will be deeper.  Price up in both.

[Oz07]

I'd be surprised if glulam is cheaper so I'd lean towards steel. I have a garage 5x5m with 45x 225 timber joists. Was looking at extending the width to 6m and I don't think you can make it work running the joists this way. I can either put a steel over garage door and run timbers 5m way, put rsj in where current 5m wall is, or you can get I beam/jji joists/posi joists to span the 6m. Would that be a solution for you?

[BotusBuild]

A quick bit of research show the Glulam to be about £50-70 cheaper, but would as @Mr Punter says would be deeper.

 

For clarity, this is an approximation of the proposed layout described above (ignore the uneven spacing of the 3m joists)

[JohnMo]

Do you have to have a flat roof? If not simple roof rafters at a low angle, then you most likely need zero steel or glulam. You just trying hard to make it more complicated and expensive than it needs to be

[Mr Punter]

It could be better as a ridge beam on a low pitched roof.

[Tony L]

I don't have the same expertise as the other contributors to this thread, but I'd have thought buying in some ready made trusses, to give a low angle dual pitch roof would be the best solution.  If you tell the truss company what your roof finish will be, they'll work out the truss spec' for you.

[saveasteading]

Have a play with this, 5m clear span gives  a few possibilities. and as it is  a garage the loads can be reduced and maybe plain timber will work.

 

That assumes that it is and always will be a garage!

 

https://www.jamesjones.co.uk/products-and-services/engineered-timber/jji-joists/interactive-span-table

[BotusBuild]

13 hours ago, JohnMo said:

you have to have a flat roof?

Yes

[BotusBuild]

13 hours ago, saveasteading said:

That assumes that it is and always will be a garage!

It will 😀 and thanks

[Russdl]

I used galvanised C section joist and timber firings for my almost flat garage roof. Maximum width of 7m reducing to 5m. 

[Oz07]

Thats a good idea are they readily available? Is there span tables anywhere?

[Russdl]

Definitely readily available, find your local metal fabricator or order direct on line.
 

As for span tables they must be out there, I however relied on the professional help of an SE (Gus Potter of this Parish in my case) to do those calculations for me. 

[saveasteading]

45 minutes ago, Russdl said:

I however relied on the professional help of an SE

And so should @Oz07.   There are overturning loads to consider, and how to fix them down.

I have no idea how to fix them to an ICF.

 

[Oz07]

I've found timber span tables you can get 63x220mm c24 to do the job on 400 centres. Expensive though. I'd be interested what works out cheaper c24 or engineered timber joists