Timber for SIPS - Regularised vs specified width

[Jamie McNaught]

Hi all,

 

So I've just discovered the complexities of getting timber to specific width. Needing to get locating and sole plates for some 100mm and 150mm sips (11mm OSB, 78 or 128mm PIR insulation)

 

Everywhere I look, timber is measured as 75, 125 (locating plate) or 100, 150 (base plates) but is actually regularised, so about 5mm less than this.

e.g:

https://www.travisperkins.co.uk/treated-timber/c16-kiln-dried-regularised-sawn-treated-timber-47mm-x-75mm/p/9000044445

 

SIP manufacturer is fine with 75/125mm for the 78/128 insulation SIP as expanding glue will bridge most of this, but obviously not 70/120mm. And you can't put a 100mm SIP on a 95mm base plate - there is not enough OSB supported apparently.

 

Am I missing something here? Can anyone point to C16 / C24 tanalised timber that is actually the full width?

 

Many thanks,

 

J

 

 

[MikeGrahamT21]

Can they not supply the timber you need direct to you? Can't be wrong then

[Jamie McNaught]

They might, but that'd be a hell of a hassle - they're a 150 mile round trip - I somewhat naively assumed they would be standard widths.... I am not sure whether I am talking about the SIP's or timber in general.

 

I've spoken to the SIP company and they've said 70mm is fine as long as sufficient expanding glue is used and the beam is directly centred.

[Temp]

Rough Sawn timber should be close to 125mm. My local timber supplier could probably cut something to whatever size you need and send it away to be pressure treated.

 

Might be a mistake to get it too close to exact size. Are SIPs straight to within 3mm?

 

 

[SimonD]

I'd suggest you contact a decent local timber merchant as they should be able to machine timbers to any dimension you need. I've had this done by two local suppliers for various bits of work. Doesn't cost much, if anything at all. They'll simply take the next size up and machine it down for you. This is a better option than relying on regularised timbers which aren't  great for framing, especially if you want good tolerances as regularised are only a nominal finished size. This is why cls is typically used for framing as finished dimensions are more consistent.

 

Edited February 4, 2021 by SimonD