buying pre-made trusses and rafters

[garyo]

I need to make a roof for a new porch / front extension, which is 4.5M x 1.8M. The roof is a lean-to design with a hip end on one end. (compliant with building regs)

Is the 'done thing' to buy the wall plates, trusses etc pre-made from a supplier who'll build them to my dimensions? Is there much to be saved by attempting to make it all myself? I like the idea of buying it as a kit to be honest!

Cheers

Gary

 

[thatbloke]

it would obviously be cheaper to make it your self but why not ask a firm for a quote then price up the raw materials your self , then you will see the exact difference in cost

 

[cumbrianroofer]

something of that size you could form yourself 4x2 timber and a measure twice cut once rule dont think you would get trusses for a porch 4.5m wide by 1.8m spar length much cheaper to do it yourself or get a joiner in someroofes would do it to included in roof price

 

[noseall]

I personally prefer to build my own cut roof. It is wrong however to assume that this is cheaper than buying trusses. Sometimes it is and sometimes it isn't.

A hip end will take a bit of thought and skill but otherwise, piece of cake.

The beauty about building a cut roof is you can build it instantly and to the exact dimensions that you wish to build it.

P.s. i have just took delivery of the 6"x2" timbers for the latest cut roof i am building and they are 7.4m long.... in one single length!

 

[garyo]

The hip joint is probably the thing that worries me the most.

Are there some fairly simple rules to follow in terms of building regs - 600mm gap between trusses, use 4x2" timber, and whatever zinc hangers you find in the local merchants?

Something I've not mentioned is that I'd like the space to be usable, for a small amount of storage, so will fit a hatch and probably lay chipboard over the insulation. Will the building inspector want to look at my truss cross section and want me to prove, somehow, that it can deal with snow/wind loads?

Thanks

Gary

 

[noseall]

Roof truss manufacturers provide calc's for their products.

Don't be surprised to find little usable space in the roof void.

 

[garyo]

Thanks Nose,

So you do your calcs yourself then?

I agree re: the amount of space. I've not actually sketched out the likely cross sections involved, so I've no idea how realistic that aim is. I don't expect to be able to get a person up there, but the kind of space you can stick a head into an keep the odd box of decorations etc.

Cheers

Gary

 

[noseall]

So you do your calcs yourself then?

A cut roof is designed and built according to span tables and is usually specced-up on the drawing, i.e. section sizes for rafters, joists, purlins, plates etc.

As i said previous, roof truss companies supply a data sheet with the truss delivery that details calculations, strap positions, spacings and node bracing positions.

Edit to add: Actually it is the structural engineer that has the final say but the architects/designers take the credit.

 

[noseall]

EDITED: oops button malfunction