Western Cedar Grading and Design Values 1

[gte447f]

I need some assistance and/or clarification on how western cedar is graded. I have a small pavilion structure that utilizes knee braces between the beams and columns for the lateral force resisting system. I originally designed 2x8 knee braces through bolted to the outside face of the beams and columns. The architect would like to substitute a fancier looking brace that will be installed in the plane of the beams and columns instead of to the outside face. The brace he is proposing is a cedar, prefabricated piece milled and stocked by a local company that does nothing else other than these types of braces, brackets, corbels, etc. in a multitude of shapes and sizes. I called the brace manufacturer to get exact dimensions and grade of lumber. The guy told me their braces were #2 or better, but he added that "cedar is not a structural wood". Of course I disagreed with him that "cedar is not a structural wood", and we had some discussion about whether or not his #2 brace was graded for structural applications or not. He ended up referring me to his lumber supplier. I called the lumber supplier, and he told me the grade was "#2 STK", which he said meant "#2 select tight knot".

It seems to me, based on what I think I know about cedar grading, that this wood may be graded for appearance only. Does that sound right, or am I off base on this? Can cedar be graded for both structural applications and appearance? The thing that keeps me from writing it off as appearance only is that the brace is milled out of 6x material, and Table 15 of the Western Wood Products Association's Product Use Manual indicates standard sizes of appearance lumber only up to 4x material.

Anyone experienced with working with cedar, please share your opinions.

 

[mike20793]

I don't know if this helps, but this is from the Western Wood Products Association (WWPA).

Western Cedars

Western Red, Incense, Port Orford and Alaskan Yellow cedars are grouped together for similar performance properties. The heartwood of these species is naturally durable against the harsh effects of exposure to the elements. They are favorites for decks, siding, planters, fences, and other outdoor amenities such as screened porches, greenhouses, pool-side structures, arbors, and trellises. The sapwood of these species also pressure treats well with preservatives for added durability.

Grades for cedar products can be very confusing to the uninitiated because every purveyor seems to offer their own grades. However, there are recognized standard and special grades for cedar products. It is important for designers and specifiers to learn the difference between ALSC-recognized grades (defined by ALSC-accredited agencies), the proprietary grades defined through buyer-seller agreements, and marketing names used primarily for promotional purposes.

Refer to the Grades & Quality Control section or the WWPA publication Natural Wood Siding Technical Guide (TG-8). The ALSC publishes a list of accredited agencies and, by permission from ALSC, WWPA makes copies available to designers upon request. (This is a list of accredited agencies, not grades and grade descriptions.)

 

[gte447f]

Mike20793,

Well, I agree with this... "Grades for cedar products can be very confusing to the uninitiated because every purveyor seems to offer their own grades."

 

[DBronson]

gte447f:

Contact the Western Red Cedar Lumber Association. Their technical people have been quite helpful to us.

Link

Regards,

DB

NB: WRC should be graded to NLGA standards in the US.