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Re: appearance grade doug fir[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: Re: appearance grade doug fir
- From: David Topete <d.topete73(--nospam--at)gmail.com>
- Date: Mon, 11 Apr 2011 13:11:39 -0700
PIggybacking on what Scott has eluded to, most DF lumber milled and sold in the western region of the US is graded by the WCLIB. http://www.wclib.org/ As for properties, I would assume for DF #1 or better, unless you/whomever spec's out "select structural." The values of each are listed in the NDS by AF&PA.
The wood should also be able to be graded for a structural grade. Assuming that you are dealing with doing "timber framing" (whether traditional timber framing with traditional mortise and tenon joints or just heavy timber with metal connections), technically speaking, the structural grading needs to be done after the members have been cut from the raw timbers (timber grading is a function of the length of the member, unlike dimensional lumber (i.e. 2x, 4x)). Thus, even if you got "select structural" timbers from the lumber yard, strictly speaking any heavy timber members should be regraded after they have been "fabricated", although that rarely happens to my knowledge...but it certainly can be done. All you would need is to have a certified grader come in and visually grade the timbers/members. Some heavy timber suppliers/timber framings have graders on staff.I will further note that for timber framing, you typically don't see grade stamps on the wood. After all, you are going to typically be leaving such timbers exposed and the owners don't typically like to see a nice, honkin' ink grade stamp "peeking" through the stain or oil on the wood members! :-) Thus, for heavy timber construction/timber framing, you tend to get the grades by way of a sheet of paper much like you would for steel grades (i.e. a mill report).Last, if it is heavy timber/timber framing (i.e. large solid timber cross sections), then the owner should be prepared for checking and splitting and such. The appearance grade only addresses things like knots and slope of grain, to my knowledge. Those timbers are still gonna shrink and distort, likely resulting in checking and splitting. This will be especially true if your project is on the inland side of the San Diego area (i.e. closer to the more nice dry desert climate with much lower relative humidity). If the timbers are a high appearance grade, then that should mean you will have little to no knots and rather nice straight grain, so there should be less distortion/warping, but you will almost definitely, if not definitely, still get splitting and checking. If you want it to be a bit more predictable (i.e. generally see the splitting and checking before installation), then specify kiln dried timbers...but that may not completely prevent future movement issues and splitting/checking. The point is the with solid lumber it is generally VERY hard to get perfectly clean looks...you will almost definitely, if not definitely, get checks and splits at least. If you want to avoid such shrinkage issues, then go with glulams...of course, the owner will have to be willing to over look the glue lines/visible laminations.HTH,ScottOn Apr 8, 2011, at 11:42 AM, karen roberts wrote:
David Topete, SE
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