Sweet Chestnut cladding

[Mike-W]

I'm planing to rebuild my shed as the old one needs to come down to move my oil tank in June, the original shed has served me well for 30+ years but now suffers from decay in a few places.
I am planing to rebuild using the traditional original cladding technique of fixing 6" x ¾" boards vertically with 1½"wide battens covering the gaps.

I have got 4 Sweet Chestnut logs felled last winter that i'm getting milled this week into 18mm boards
AND I know its a year per inch to Air Dry timber (I have brought freshly sawn wood and sticked it many times to season it previously).

However time is against me on this, as I said the S/C is being milled this week and i hope to start rebuilding in July, so my question is this:
Once milled and sawn into 6" widths do I stack it all face to face so it remains green until i'm ready to assemble it then allow it to dry out once fixed, or do i sticker the boards for a few months to start the seasoning process before fixing?

Shrinkage across the boards is not a problem as the boards dry as i'll be covering the joints with battens. From past experience of sawing S/C from our wood most of the problems (tension & splits/shakes) show up as soon the boards come off the mill.

So i'm inclined to dimension the sawn boards then cover them until i'm ready to use them , any thoughts or experience of using timber green for cladding guys?

 

[MikeG.]

Vertical boards so horizontal battens behind (ideally with an outward slope to the upper edge), on counterbattens behind that to maintain a continuous air gap to the structure, but I digress.

It isn't (just) shrinkage you are going to have to deal with if you apply cladding which is green, but the differential drying between the exposed and the hidden faces which will inevitably cause cupping. Personally I would stack the boards until they are properly dry, leaving the workshop part-built, but covered in a breather membrane, battened down. The building will be fine, although looking unfinished, but green wood cladding cupping in the sun will be so bad it will pull the fixings out. I've seen buildings where this has been done, and where many of the boards were sticking out 4 to 6 inches, ruined.

 

[Mike-W]

Thanks MikeG,
Once assembled the shed will be south & west facing so i could run into issues with the sun 'cooking' the cladding , I had thought distortion while drying might be a problem hence my 'solution' below.

The shed frame will be constructed from fully seasoned (AD) Sweet Chestnut, something like 40x50mm section at approx 600mm centres running horizontally onto which the vertical 150mm wide cladding will be laid. i'm thinking of fixing these in place with the overlap weather proofing battens screwed through the vertical gaps using decking screws into the horizontal frame mentioned above.

I had a piece of thin section (6mm) S/C that was sawn in the last fortnight from a log felled last winter, as a test i left it out in the recent hot weather unsupported and it did twist a little over its 6ft length, but it was not as twisted as i thought it might, meanwhile the moisture content was reading below 10%.
If I can get the sawn cladding into stick by this weekend it will have at least 10 weeks drying before I get the shed frame constructed and need to start the cladding. At that point I can check the sawn boards for moisture content & movement then review my options.

 

[MikeG.]

If you wrap the frame of the building in a breather membrane then you will be under no time pressure at all to fit the cladding, and thus you'll be able to fit it when it is dry enough not to be prone to cupping. I wish I had taken a photo of the worst example of green timber cupping I've ever seen, on the office building of a supplier of seasoned oak. You could easily pass a clenched fist through the gap under some boards, and this despite them being screwed on in the first place.

Your suggestion for fixing the boards is the only sensible way. You could also screw at one edge of the broader boards, adjacent to the cover strips. I've designed 2 or 3 buildings which use such a method, and it has worked well. One of them is 7 or 8 years old now, and problem-free.