Roofing help please...

[davic]

Hello again!

I am interested in making a gambrel roof for a shed which is around 6x4m. I have made a cut roof with hips on a small scale just for a bit of fun (yes it has come to this...)

Does it have to be based on a semi circle to have structural integrity? I'd like to bend the rule a bit to lower the overall height. I'd have to do the calcs myself this way instead of using one of the online calculators but, I'd be OK with that.

All help appreciated

Dav

 

[kostello]

The weak point is on the corners....... You need to find a way of bracing it so they can't spread.......

 

[blackrodd]

I have never done one. I googled Gambrel roof and it's all on there, second one down is the calcs,
But in good old english, (Imperial, to you)! apparently.The dvd looks useful, too.
I would draw it out on a sheet(s) of ply, full scale, make that into a truss jig and get the chop saw and nailer going!
If you have done a cut roof, this ought to be a doddle!
Galvanise brackets to the the truss feet, screwed each side, would help skew nailing issues!
Don't forget the wip please!
Regards Rodders


PS, Expamet do nailing plates for timber connecting for this very situation, there are others.
Or maybe get you're local truss manufacturer to give you a quote and you may find the price cheaper than you can get CLS timber for.
You may find the truss people have given you a lot of valuable free info too!
Rodders

 

[davic]

Cheers guys. The carpentry I am OK with. I don't want to "design in" a weak structure

I could use: http://www.blocklayer.com/Roof/Gambrel.aspx

But I want to break the semi circle to lose a bit of height. I am wondering would this make the roof inherently weak? I appreciate that I might not be making a lot of sense though.....

 

[blackrodd]

Thats the one! Down the page tells you how to do what you are thinking of,
But does mention about alterations of the angles/sizes may not be acceptable for building regs,
If you got that far and maybe this does, or does not, concern you at all.
Hopefully someone here can advise you further on any design alteration to lower the roof height.
Regards Rodders

 

[fluffflinger]

I would have thought you would be fine but the bracing is vital.

I have a Gambrel Roof on my modest workshop it was designed to please my eye and give me more room in the "roof space" for storage purposes, I'll add I am a total amateur and have no construction industry or roofing experience at all but I have built boats so I do understand what works in terms of stiffening structures etc.

I simply braced the inside of joint with a piece of timber and then glued (epoxy, because it has no equal in strength) and nailed on ply plates either side of each joint.

Been up for five years and no spread. I do have the two sides of the building tied together by structural timbers that support a storage platform at the top of wall height, This I assume helps resist the weight of the roof pressing down and trying to spread the trusses.

Building is 4.8 metres wide and the roof is quite flat in section, the apex would not sit in a semi circle, if that is the rule of thumb???

You could always get a structural engineer to give you the answer?