help with size of wood for rafters

[b21playa]

For my garden shed/garage, i want a pitched roof with a slope either side.

I know 4 x 3 is ok for wall plate but what about for rather and main ridge joist?

The ratfers will need to be about 12foot long anf the ridge around 19foot

Thanks

 

[^woody^]

125 x 50 at max 450 centres

200 x 25 ridgeboard.

If you are not having any horizontal bracing (ceiling joists or collars) then a ridge beam (102 x 178 UB) may be necessary to prevent sag/spread of the rafters. But probably not for a shed/garage

 

[b21playa]

125 x 50 at max 450 centres

200 x 25 ridgeboard.

If you are not having any horizontal bracing (ceiling joists or collars) then a ridge beam (102 x 178 UB) may be necessary to prevent sag/spread of the rafters. But probably not for a shed/garage

Was thinking of put another ridgeboard type beam across half way up the slant, which sits underneath the rafter. It will support the weight midway and stop any sagging as the rafters will be tied to it.

Alternatively was thinking of cross bracking not for ceiling joists but higher to keep it rigid

 

[^woody^]

Your "ridgeboard type beam" is aka a 'purlin'.

If you do this, then the purlin will need supported at stages along its length, or that too will sag. Then you end up with double beams and posts and ties and everything to support the purlin

Your cross bracing idea does nothing to stop sag

 

[b21playa]

Your "ridgeboard type beam" is aka a 'purlin'.

If you do this, then the purlin will need supported at stages along its length, or that too will sag. Then you end up with double beams and posts and ties and everything to support the purlin

Your cross bracing idea does nothing to stop sag

how can I prevent sag?

 

[^woody^]

..... the purlin will need supported at stages along its length,...... Then you end up with double beams and posts and ties and everything to support the purlin

 

[noseall]

how can I prevent sag?

deeper rafters.

 

[b21playa]

how can I prevent sag?

deeper rafters.

How much deeper?

Also whats the price of rafters this size, roughly 13 ft?

 

[cb9002]

Numpty question... what's a ridge beam and how does it prevent spread?

Thanks!

Oh, and playa, have you got a quote for trusses? Might be a lot easier!

 

[cb9002]

Oh, and I was at B+Q, they sell 12 foot 6x2 for 14 quid.

Should be a good guess for you!

 

[Deluks]

Oh, and I was at B+Q, they sell 12 foot 6x2 for 14 quid.

Can get for half that at many timber/builders merchants.

 

[b21playa]

Oh, and I was at B+Q, they sell 12 foot 6x2 for 14 quid.

Can get for half that at many timber/builders merchants.

God at £14 the roof will cost be a bomb

I bought a length of 4x2 for £4 from a local place and it was about 16ft long, so hoping some 6x2 will be around the fiver mark for a shorter length and purchase in quantity