OSB/cladding detail on garden room build

tawfeeredux

I'm trying to figure out the details of a timber framed garden room build and one item that I can't see an answer for either in the garden room threads on here or in the various youtube channels is how the bottom edge of the OSB sheathing is protected from the elements, or if it even needs to be.

The sketch below is roughly what I'm working towards. I know the cladding will protect it against rain, and keeping the frame up c.150mm from the ground combined with a pebble surround will protect against rain splashback, but does it need to be protected against, I dunno, atmospheric moisture?

Is it enough to bring the breather membrane down over the end of the OSB & if so what do I attach it to? Or loop the vapour barrier for the floor around the bottom of the OSB sheathing? Or just treat the edge of the OSB with a sealant?

autumnalcore

Perforated strip to maintain ventilation and keep out insects, animals

Cembrit detailed drawing in here
https://www.cembrit.com/media/2034274/cembrit-plank-and-panel-installation-instructions.pdf

Cedral

autumnalcore

OSB edges are supposed to be sealed also, you will see varying advice epoxy, polyurethane, silicone etc.

If you were being super anal you could tank the bottom few inches to protect against rain splashback.

listermint

Never seen cladded OSB sealed or tanked . If you needed that then you haven't provided breathing room or exits for water and you have a bigger problem.

That's complete overkill.

autumnalcore

listermint wrote: »

Never seen cladded OSB sealed or tanked . If you needed that then you haven't provided breathing room or exits for water and you have a bigger problem.

That's complete overkill.

If exposed edges are cut edge they should be sealed and yes the tanking is overkill hence I said super anal

listermint

autumnalcore wrote: »

If exposed edges are cut edge they should be sealed and yes the tanking is overkill hence I said super anal

They're not exposed though hence the layered design. Osb edges by their nature are cut edges it's in the manufacturing.

If you build this so you see any osb..... You've done it wrong.

tawfeeredux

listermint wrote: »

They're not exposed though hence the layered design. Osb edges by their nature are cut edges it's in the manufacturing.

If you build this so you see any osb..... You've done it wrong.

I suppose my worry was that even if I built it as per the sketch and the osb wasn't visible, its edges are still, if not exposed, at least open to the air. Granted it's very sheltered. I think I was overthinking how much moisture could get in there that wasn't rain. And as you say the vent and the space for water to run off takes care of any moisture that did happen to get in.

Lumen

The exposure is from rain splash

PMBC

Tawfeeredux I like your graphic - how/using what did you do that?

PMBC

Tawfeeredux, I like your graphic - how or using what did you do that drawing

tawfeeredux

PMBC wrote: »

Tawfeeredux, I like your graphic - how or using what did you do that drawing

It's just Excel.

PMBC

Thanks.
Shows my level of ignorance - didnt know you could draw with Excel:o

Wow. Tried that. Its very simple.
Still learning.