shed roof specs

[David]

Hi,

I am trying to determine the size of beams that I would need to use on a shed roof.

Any one know of any sites that give info how to work this out

The shed I am going to build is a workshop that will be 3.6m x 4.8m with the ridge in the same direction as the short side - 3.6m

The front of the shed would be the 4.8m edge

I though that I would need 5 horizontal beams: one at the apex one at each side and one half way alone each side of the roof

What dimensions would these beams (3.6m) need to be.

If I extended these to give an overhang over the front of the shed would the same dimensions be required and would I need to extend all 5 beams over the front or just 3 of them...

any hints and tips would be useful.

I have the "Building a shed" book by Joseph Truini but it doesn't give much away in the requirements of roofs...

Thanks David

[AlexW]

If you don't get a better answer than this ...

I built an approx 5x2.5m garage last summer and chose the timber sizes mainly by looking at similar structures manufactured by various 'proper' companies.

Its still standing!

So why not take a trip to your local garden centre or sectional building supplier and see how they do it.

FYI: if my garage had not had several special requirements then I would have bought something sectional or in kit form though ... might be an idea? I don't think it would have cost all that much more in the end.

HTH,

Alex

[Lurch]

On Fri, 11 Mar 2005 17:29:11 +0000, David strung together this:

I've just extended my shed an the calculation I used was;

woodthat happened to be in the garage + some other wood I bought = a shed!

Basically, 2"x2" or similar would suffice.

[John Rumm]

If you want to get really technical you could use superbeam from SDA (demo available here

but that would probably be massive overkill in this case.

yup

in effect this is provided by the walls. A couple of cross braces that run from side to side are handy to stop the weight of the roof pushing the walls apart though.

A "pulin" in effect. Only any use if you support this at both ends and at least once (preferably twice) along its length. The classic roof truss arrangement can work well to solve both of the above:

/\ A/ \A /\ /\ /==\/==\B / \

Cross brace at B, purlin at A supported by a strut from the cross brace.

I built a (smaller 2.5m x 4.5m) workshop all in 3x2", which is very strong (way more so the off the shelf sheds). In your situation I would be tempted to go for 4x2"... this would also be typical for a real tiled house roof carrying several tons of tiles - so ought to be plenty good enough for a shed.

better to do all of them...

There are some piccies from the one I built that may be of use to you here:

I have the "Building a shed" book by Joseph Truini but it doesn't give

It wants to be strong enough to support itself and you!

[Malcolm Race]

As a crude measure for a floor beam 2" wide you need a depth (in inches) of twice the span (in feet) + 1 at 18 inch spacing. I suspect that, unless you are going to dance on the roof, 2" depth will be adequate.

Malcolm

[Tony Bryer]

^^^^^ ITYM half

[bigcat]

Your enemy is sag, not collapse. At that length youll probably get 4-6" of sage before collapse.

Anything that doesnt sag too much would work. The one gotcha is what happens when youve got 4" of snow on the roof. sizing correctly will ensure it doest collapse under snow, large roofed home made structures can.

5 would be sensible.

no extra size needed, unless youre making a real big overhang.

You can make sheds out of anything. You can even make them from nowt but bottles, if you have some strange reason to want to. I once saw a house wall made from glass bottles.

NT