Plywood sole plate - bonkers or....?

[maxdavie]

I've been reading through TRADA's guides on sole plates and other guidance, plus previous discussion on this forum. 

 

I'm now pretty skeptical about the sole plate being built to the correct dims. All the corrective measures to ensure its level etc also sound very onerous and time consuming. 

 

The cnc machine will cut all the parts that make up my wall cassettes with 0 tolerance. 18mm thick WISA Spruce ply itself will have a +/- 1mm across its thickness. Essentially, the tolerance of the sole plate will need to match the tolerance of my cassettes - 0! I'm also going to make a tweak to my system, so the front and rear panels of the cassette extend down to slot over the sole plate (see indicated in red over the detail) - I think SIPS works like this too. Anyway, that just increases the need for the sole plate to be the right dim. 

 

So, I'm toying with the idea of a cnc-cut plywood sole plate; double layered, exterior grade (or even marine grade) staggered and glued together. I'll know that right angles are true and dims are mm accurate. After bonding it'll all form one continuous piece. It won't arrive warped. It will still need packing underneath I imagine - maybe structural leveling mortar or whatever the SE's specify. It'll cost more to produce I know that. 

 

There's still a lot more research I need to do and I need to get the SE's view. I'll continue to mull it over....

 

Thought I'd see if anyone had any thoughts. I'm sure this is pretty rogue! 

 

 

[Mr Punter]

With the detail you have you will probably need to bed the Marmox in mortar and that would be the best time to ensure it is level.  Treated CLS softwood - either 38 x 89 or 38 x 140 is pretty standard for sole plates and considerably less costly than your ply.

[maxdavie]

It works out at £7-10 per linear meter like this

[maxdavie]

24 minutes ago, Mr Punter said:

you will probably need to bed the Marmox in mortar and that would be the best time to ensure it is level. 

Ahhh brilliant thanks! 

[Thorfun]

our TF sole plates sit on coursing blocks and, as @Mr Punter said, it was at this stage that I was standing over the brickie ensuring everything was as level and square as possible to give the TF the best chance of fitting!

 

I think the TF company needed to use packers in only 1 small bit where the brickie went awry as he didn't have the self-levelling laser level! 🤦‍♂️

 

in the end the TF company said the coursing blocks were spot on and it made the sole plate fitting a breeze for them which they (and I) were very happy about.

[Thorfun]

41 minutes ago, maxdavie said:

It works out at £7-10 per linear meter like this

38mm x 140mm CLS is cheaper than that.

 

first site I found not far from me shows headline figure of £5/lm. I'm sure that could be reduced with quantities.

 

https://www.mstc.co.uk/ex-50x150-cls-38-x-140-fin-sizes-4-8-only-70-pefc-certified-bmt-pefc-0277-cls26

[maxdavie]

13 minutes ago, Thorfun said:

first site I found not far from me shows headline figure of £5/lm. I'm sure that could be reduced with quantities.

Yh CLS is no doubt cheaper. I need to think about extra cost vs speed/accuracy etc