c16 and cls: what are they?

[Stephen]

Hello,

I was just wondering what does CLS stand for and C16? I think these are the timbers used for stud walls?

I bought some C16 for a stud wall I was repairing. I've read the wiki faq and it says not to use 1.5" x 2.5" wood but isn't that the size of C16?

I had no choice because I was repairing a wall that was already in place and that was the size of the timber used previously.

I see that the wiki recommends 3" x 2" to be used. I presume you insert it 3" deep and use the 2" face to attach the plasterboard to?

Thanks, Stephen.

[The Medway Handyman]

CLS stands for Canadian Lumber Standard. Its to do with the structural strengh of the timber I think. C24 being stronger than C16 for example.

Someone more knowledgeable will be along shortly...

[dom]

Pretty much as MH says, c16 is the common basic grade for structural timber, c24 is a higher grade to be used where structural calculations show it's necessary.

For your (presumably non-structural) stud wall, it doesn't matter which you use.

[John Rumm]

C16 (and C24) are stress graded kiln dried sawn timbers typically. C16 being the basic level of stress grading commonly found. You can use the specification in structural design packages like superbeam to design structures that will meet the requirements of the building regulations for strength, and deflection etc. A C16 marking means that the timber will achieve a certain level of strength (give or take a statistical allowance for natural variation).

CLS (canadian lumber standard) aka "regularised" timber is a lightly planed construction timber. Its a little smaller in size typically, but has a smother finish and no sharp corners. This makes it safer to work with in theory. I don't know if it is also stress graded.

No, C16 is available in any of the standard sawn sizes. Stud walls would typically use 4x2" or 3x3" (100x50mm or 75x50mm). These can be real sawn dimensions or the slightly undersized CLS versions.

Yup. I would say that 4x2 is actually a more common size with older properties. It also matches the most common door lining size when used with 1/2" plasterboard each side.

[The Medway Handyman]

I'd disagree John. Wickes for example only stock 38 x 63 or 38 x 89, as do B&Q. Albeit these are finished sizes, C16 certainly isn't readily avaialble in all standard sawn sizes.

[John Rumm]

Well I suppose it depends on your definition of standard sawn sizes. I have never had any trouble buying C16 in 3x2, 4x2, 6x2, 7x2, 8x2, and

8x3 - i.e. common joist sizes. Buying C24 is harder - I needed some of that when I did my loft and had to order some which took a week.

(I would not consider what Wickes carry to be much of an indication of availability though - they tends to have quite a small range in many things (although quite often reasonably well priced basic building materials for what they do have. )

[The Medway Handyman]

Never seen it it any other sizes, but then again I've never needed to look.

Agreed, they stock basic stuff, but I don't tend to need to visit builders/timber merchants much. I guess 'readily available' and 'available' are different things.

To me, given what I do, Wickes are 'heavyside' :-)

[PeterC]

Wickes' timber is generally better (less bad) than B&Q's. I could have saved over £100 on my last lot (lower prices and wrinklycard) but used Wickes (and had luck with a reduction halving the difference) after looking at the timber.

For fitting a larger loft hatch I wanted good timber for the new surround and that from Wickes is almost free of faults in the relatively short runs used, so I didn't worry about category.

[Phil L]

C16 merely refers to the grade of timber and has nothing to do with size.

C16 has less knots and imperfections than ungraded timber and is commonly used in roofs and other weight bearing situations. C24 has less knots and imperfections than C16