Timber framing advice

[Steve Maskery]

Actually that makes sense. If the top cannot press down then the bottom cannot push out, is that it?

I have to admit I first read that as "if you use a structural ridge you don't need any tiles in the roof...", but then I don't have my contact lenses in right now...

 

[kostello]

structural ridge......if the ridge can't sag the walls can't spread.......

used one on my girls playhouse............ 2 6*2s supported on posts at either end....

and glulam ones on other projects too

steve if your new workshop has gables at either end you could have all that clear space.......

 

[kostello]

oh and if you don't want to clad the thing in ply or osb you can do let in bracing or just brace the last stud bay at either end across opposite corners

 

[Steve Maskery]

I'm having raised-tie trusses. At least, that's the current plan!
S

 

[angelboy]

Ok Ok Ok.

How about this one.

100 x 50 sole plate
100 x 50 uprights & gable ends
100 x 50 top plate
200 x 50 ridge beam
150 x 50 rafters - Maybe I'll put a collar across the rafters just under the ridge.

9mm OSB external & internal faces of walls
9mm OSB external & internal roof

 

[EBH1]

Looks good. It'll not blow down in the wind!

My suggestion earlier of OSB on the internal faces in a personal preference as it allows for easier fixing of shelves etc. Some engineers drawings I've worked from over the past little while have asked for double sheathing on the gables of timber buildings where a structural ridge beam is used. Perhaps doubling up the stud below the ridge beam support right down to the wall head would also help the structure.

 

[angelboy]

OK - Sound advice.

Another thought, Could I just use the OSB internally to help tighten the frame as outside I'llbe cladding it in 150mm feather edged boards. Same with the roof, I'd be battening it out with 38mm battens.

I'm thinking that that might be OK. Otherwise I'm sort of strengthening it twice if you see what I mean.

 

[Steve Maskery]

The OSB adds bracing, which the featherboard does not. At least, not very much. So if you are reying on one internal layer, I'd make it a bit thicker than 9mm.
What does your structural engineer suggest?

This is an interesting discussion.
S

 

[EBH1]

Yes OSB on the inside will be just as good as the outside. If you're insulating the shed it's worthwhile tacking up some thin polythene on the warm side of the insulation to stop any interstitial condensation.

9mm OSB will be perfect. It's pretty much industry standard for sheathing. The only time I've had 12mm spec'd is for sarking.

 

[Steve Maskery]

EBH
I've no wish to hijack AB's thread, but can I ask you a q? Would you still use 9mm OSB on a build like mine, 8m x 8m, 3m to the eaves? And can I ask you, without in any way meaning to cast aspersions, what your expertise is in this? Seriously, no slight intended.
I'd ask my structural engineer, but I don't have one.

S

 

[angelboy]

I'd ask my SE but the last time I threw some drawings his way it cost me £600........For a shed, I think I'll make do!!!

 

[EBH1]

Hi Steve,
Since leaving college I've worked in the building industry and focused on timber kits. All the timber kits I've built have been detailed using 9mm OSB as the sheathing. Ply is also a good alternative, but prohibitively expensive.
My own house extension is 7.6 x 4.8 and 4m to the eaves. The structural engineer specified 9mm to all walls and 12mm as sarking on the roof. If you PM you're email address I can forward you a good PDF by TRADA which has a few good details for modern timber frame construction.
Euan

 

[angelboy]

I was going to put a breather membrane on the inside ad a vapour barrier on the outside.

 

[Steve Maskery]

Yes, well, I understand where you are coming from.
Valuable advice on this forum, isn't it?
S

 

[kostello]

Double or triple the ridge, maybe use a Fitch beam

You don't need OSB inside and out just 12 mm on one face to brace it

Fix some metal strapping over the ridge onto the rafters and fix with lots of twist nails


Edit to add what are the dimensions? Or have did I miss that?

 

[kostello]

Steve I am pretty sure that technically you only need to brace the corners to prevent racking of the frame but the reality is that it is easier to board the whole frame