garage roof

[caseyjones1961]

Can anyone please give me an opinion of my home made roof trusses....good,bad or indifferent?
Just want to added that the uprights on the main framework have now been doubled up and there are an additional 6 purlins per side of roof, I can get some better pics but its all tarped up at the moment.

Untitled

• caseyjones1961
• 11 May 2014
• 1

Untitled

• caseyjones1961
• 11 May 2014
• 1

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[ladylola]

Look fine to me. What roof covering are you going for ?

 

[foxhole]

I would add vertical timbers to apex and tie timbers to all to prevent warping and twisting once under load.
Example here
https://environment7.uwe.ac.uk/resources/constructionsample/Conweb/house_ages/elements/section5.htm

 

[Norcon]

A small shed that size all you need is a truss either end and span the purloins with 7" x 3".

 

[EightyTwo]

Your braces support the last quarter of the rafter - it would be better if they were joined to the rafter in the middle, under a purlin. Just think where the forces are going - with 3/4 of the rafter unsupported, it may well sag.

Since I can't see the beam very well, it's difficult to tell whether all the forces from the braces will cause it to bend. A vertical piece, as foxhole suggests, between the beam and the ridgeboard will act in tension, effectively holding the beam up. This would make it similar to a Kingpost truss in foxhole's link.

The do look very pretty and jolly strong, though!

 

[caseyjones1961]

Thanks for all the positive responses, Eight two if by "the beam" you mean the ridge board(your terminology is probably better than mine) if you look closely in the second pic there is another horizontal brace between the two diagonal braces snugged up against the ridge board and sitting on the ends of the diagonals(screwed through as well) but I take on board your comment about the unsupported section although the rafters are two 4x2's side by side and there now 7 Purlins (2x4's) on either side running at 90 degrees to the rafters so all in all pretty strong I thought but I will revisit that again when I get chance before I board it over.

Norcon...the "shed that small" is 20ft x 20ft so,correct me if I'm wrong, but I don't think 2 trusses would cut it...too late now anyway as there are 7 trusses already in place!

Ladylola....will be covered in 19mm WBP ply, underfelt membrane and felt shingles so not mega heavy but hopefully substantial.

One other thought is should I add the external sheathing before I start climbing about on the roof?...although I'm sure it will bear my weight there is a bit of a sway to the whole building which will hopefully be eliminated once I start adding the external sheathing and cladding etc...but I really wanted to get the roof buttoned up with at least the membrane on to get some degree of weather proofing.

Thanks again everyone...any other comments much appreciated

 

[EightyTwo]

By "beam", I meant the joist along the bottom of the truss. I had seen the short tie across the top, under the ridgeboard - a good idea - but I still think that the diagonal brace should go to the middle of the rafter.

7 purlins 4x2 is seriously macho! I'd have thought that 2x2 would have been fine. You could easily walk on them once they're fixed.

You say that there's "...a bit of sway..." in the building. Why not add planks on the underside of the rafters running from the ridge at one end to the eaves at the other (more triangles!) and vica versa on the other side. Look at foxhole's link again, at the modern trussed roof. You can overlap planks (side by side) if they're not long enough. You could also remove them after you've fixed the plywood, if you want. If the whole building is twisting, put some temporary diagonals on the walls, too. Make sure that you check that it's all square before you fix them, though..!

 

[noseall]

My only criticism is that the two chords joining the rafter to the joists would have been better positioned so that the hit the rafter more mid-span (as said) and that they also connected with the joist somewhere close to 1/3rd span also, as opposed to in the centre.

 

[noseall]

One other thought is should I add the external sheathing before I start climbing about on the roof?...although I'm sure it will bear my weight there is a bit of a sway to the whole building which will hopefully be eliminated once I start adding the external sheathing and cladding etc...

Make sure the building is square, upright and true before you screw your fist piece of sheathing ply. You will not budge it once it is on.

The building can be easily braced with some diagonal 4" x 1" added temporarily to the uprights. It would be a good idea to add some temp' bracing to the inner skin and at the same time make sure everything is true before you fix. This leaves you free to add the external ply without any uprighting worries.

 

[caseyjones1961]

Thanks again for the tips...complicated this roofing lark!
I added some more supports today midway along the rafters down to what I call the cross beams...no pics but will add some when I get the tarp off over the next couple of days
Now I've just realised that what I've been referring to as "purlins" aren't true purlins at all as mine are added to the OUTSIDE of the rafters....my "design" was based on a twenty year old plus stable that we inherited from the previous owners....much lighter structure on a roof almost the same size and that seems to have lasted.
Is there any value in adding "noggins" or using those herringbone straps between the 6x2 cross beams or would that be overkill?
Noseall thanks for the tip about checking the building for trueness...got my framing square ready...intending to crack on with sheathing over the next few days...will post a couple more pics for those that are interested

 

[ladylola]

Ladylola....will be covered in 19mm WBP ply, underfelt membrane and felt shingles so not mega heavy but hopefully substantial.

One other thought is should I add the external sheathing before I start climbing about on the roof?...although I'm sure it will bear my weight there is a bit of a sway to the whole building which will hopefully be eliminated once I start adding the external sheathing and cladding etc...but I really wanted to get the roof buttoned up with at least the membrane on to get some degree of weather proofing.

Thanks again everyone...any other comments much appreciated

Similar to my own workshop save for mine having coroline sheeting rather than shingles. The trusses are very similar to mine as well although my braces are nearer to the centre of the rafter and the ties are made of two pieces bolted together , each being something like 2/3 of the span ( no real reason other than I was using what I had rather than buying more). My workshop has been up about a decade or so without problems or movement and I also tend to stack a fair bit of timber on the trusses too.
I'd also fix the wall sheeting first before the roof. If you are worried about keeping out the weather staple some visqueen ( thin clear plastic sheeting) onto the roof.