Building or buying trusses

[Joe Shmoe]

Hi folks.

New workshop build starting, just working out the details but looking at 3.6m wide by around 5m.

For my several outbuildings I've always built trusses with a raised chord to give me an extra 100mm of headroom, generally constructed in 4x2 treated with 9mm plywood gussets. No king post etc. not had any issues do far, but then my widest build has only been 2.8m and heaviest covering has been box section sheets.

This time I'm considering man made tiles or something with low maintenance and longevity, and therefore more weight.

I'm wary of just knocking up some random trusses with that span and weight, would online truss manufacturers be the way to go? Just did a quote and it's over £600.

Any views? Would my ill designed 4x2 be stronger than their properly calculated matchstick design? I could probably knock mine up considerably cheaper.

Cheers.

 

[tomf]

You should have got a design with your quote, you could just use their dimensions to replicate, if their seizes are under 4x2 then there is no problem just do it the way you did it last time.

 

[mindthatwhatouch]

Be careful replicating sizes from a truss manufacturer. Theirs could well be less than 4 x 2 as the strength comes from pressure clamped nail plates at the joins.
The TRADA table I have (IIRC) gives a 1.8m max span at 600mm spacing, based on roofing tiles/slates.
I reckon 4x2 with some decent plywood gussets will be fine for a workshop as long as you don't load it up too much. i.e. not concrete tiles or loads of storage hanging from the rafters.
Having just used some Decra tiles I would really recommend them (or Metrotile a similar equivalent) Have you thought about a structural ridge beam, decided to go along this route to keep that extra headroom. Have a look at my workshop build
https://www.ukworkshop.co.uk/forums/yep-it-s-another-workshop-design-questions-t84326.html for details as mine was 4m wide rafter span 2.3m ish.

What's the location like, very exposed?

HTH best of luck

 

[blackrodd]

Look at this link, it should answer you're question, Nail/screw the rafter top, then nail/screw, on the skew,
2 each side
https://www.google.co.uk/search?q=rafte ... L5X3nNw%3D
Cut the rafters from a pattern,plumb cuts and ends, so they are all the same fix using truss fixing clips at the birds mouth/ seat cut end, see below.
http://www.tradefixdirect.com/builders- ... AtU_8P8HAQ
HTH Regards Rodders

 

[MMUK]

Personally I'd build a traditional A frame roof using 6"x2"