larch cladding from small(ish) logs

[Welshfred]

Hi, I'm hoping to mill cladding boards from larch but quite small diameter, 12inch dbh max. The boards will therefore contain heartwood, is this a problem? I've heard boxed heart can be an issue... Bit worried about warp across the board too (cupping?) or do you think this risk can be sorted with good drying and fixing?

Have done a search, lots of good info but not quite what I need to know. Cheers!

 

 

 

 

[Daniël Bos]

Afaik, it's the sapwood you want to avoid.

Boxed heart can split and warp, but cladding tends to be so thin that provided the board are flat when you stick them on, the fixings should stop the warping.

They'll be exposed to the weather on one side, and dry on the other, so there will always be some movement.

If possible, cut board from bigger trees.

[Squaredy]

Yeah totally agree with Daniel Bos, using the middle of the log isn't a problem.  Do expect some cupping, especially if you will be using boards 9 inches wide or more..  If you can stick to narrow boards (say 6 inches) you will get less movement.   And of course allow for some shrinkage when you fit.  If you fix a wide board top and bottom it may well split as it dries.  Fix it top only, or top and middle (that's horizontal cladding I'm talking about).

[Welshfred]

Thanks both. Thats all good to know. I will have some larger timber but its prioritised for other elements of the structure so hope to get the large amount of cladding done out of my commonest tree size. I would imagine boards cut from a larger log, away from the core will run a higher risk of cupping due to the grain orientation - any thoughts on mounting these, convex vs concave to the outside? I reckon convex to reduce the risk of gaps opening between boards... cheers!

[CDMR]

If you mount them so they warp convex they will deflect the plank above. This will put more pressure on the fixing and risk the boards coming loose.  If they are concave a gap is created but the water would just drip off further away from the wall. FWIW I'd go concave.

[Rough Hewn]

Quartersaw it. No cupping.

 

[Welshfred]

V

2 hours ago, Rough Hewn said:

Quartersaw it. No cupping.

 

Yes, if the timber is available, but most of what I have is too small for quarter sawing. What larger trees I have may need to be reserved for larger sawn sections or roundwood framing poles. Its all 50s planted Japanese larch, unthinned till the 90s so not many stems have reached good size.        

4 hours ago, CDMR said:

If you mount them so they warp convex they will deflect the plank above. This will put more pressure on the fixing and risk the boards coming loose.  If they are concave a gap is created but the water would just drip off further away from the wall. FWIW I'd go concave.

This thought had been niggling. Aiming to secure the boards at suitable intervals, prob 600mm would help keep them flat I hope, and not create gaps for wasps etc to enter the wall cavity. Concave could well be better structurally. I will look for some real world examples locally... Not cutting or building for a while yet (2019 probably) so hopefully plenty of time to work all this out. cheers!

 

 

3 hours ago, CDMR said:

If you mount them so they warp convex they will deflect the plank above. This will put more pressure on the fixing and risk the boards coming loose.  If they are concave a gap is created but the water would just drip off further away from the wall. FWIW I'd go concave.

 

[Rough Hewn]

If you're not starting til 2019, I'd be sawing now. Stack it to air dry for a year, then get it kilned to about 10% mc. By the time it's out the kiln for a few weeks you'll know what's cupped/split etc. Less surprises after installation.

i also presume your cladding is approx 25mm thick?

 

[Welshfred]

 

Yes, planning 25mm thickness. I like the idea of starting now in an ideal world but I have grant aided work to finish under contract which will keep me busy in the woods up to early winter 2018, then I can start on felling for building. First priorities will be roundwood framework and studwork, hopefully all from my own timber. Some long length 6x2 etc will have to be bought in in, then i'd hope to get on cutting cladding. Kilning? For exterior use? Other threads on here suggest using green or with minimal seasoning and relying on the fixings to studwork to hold the boards flat, full seasoning in situ from autumn onwards. Bearing in mind the op  concerned through and though cut boards from centre of log so less prone to cupping. Given common tree sizes here these will likely be 6-10"  wide ripped down to 8" max probably. I plan some experimental cutting this autumn though and could follw up with some experimental mounting. I have a shed to build too so good opportunities for practice. Cheers!

[Rough Hewn]

Stack the stickers 12-18" apart,

helps reduce cupping.

put a balanced heavy load on top of the stack/ use ratchet straps.