Construction Plans: How to Improve Clarity of Framing Lumber Specifications
Construction Plans: How to Improve Clarity of Framing Lumber Specifications
(OP)
A simple specification such as No.2 KD-19 XYZ-species may no longer clearly communicate to other parties what products and design values were assumed and used by the RDP in their design work and thus required for the project. For example, see 2024 NDS Supplement, new Table 4G, starting on p. 63 for lumber made in the U.S. and around the World at the AWC website: https://awc.org/pdf-viewer/?idp=1413&idf=4
The authors suggest a more robust specification as published in the Structure Magazine: https://www.structuremag.org/?p=23897 Your comments are valuable and greatly appreciated.
The authors suggest a more robust specification as published in the Structure Magazine: https://www.structuremag.org/?p=23897 Your comments are valuable and greatly appreciated.
RE: Construction Plans: How to Improve Clarity of Framing Lumber Specifications
How can it be grade marked as Southern Pine if it has a G value so low as to cut connection capacities almost in half? I must be missing something here.
RE: Construction Plans: How to Improve Clarity of Framing Lumber Specifications
"All wall framing lumber shall be 2x4 KD19 No.2 SPF or Btr."
consider this spec:
"All wall framing shall be 2x4 KD19 No.2 SPF (Fb/875, Ft/450, Fv/135, Fc-perp/425, Fc/1,150, E/1.4, and G/0.42) or Btr."
Assuming you used and want to specify 2x4 No.2 KD19 Southern Pine wall lumber listed in NDS Supp. Table 4B, consider the same format:
"All wall framing shall be minimum 2x4 KD19 No. 2 Southern Pine, with minimum reference design values of: Fb/1100, Ft/675, Fv/175, Fc-perp/565, Fc/1,450, E/1,4000,000 and G/0.55."
Do you feel the longer format including the NDS Supplement tabulated allowable design values strengthens the specification for all parties involved in the construction process?
RE: Construction Plans: How to Improve Clarity of Framing Lumber Specifications
Not only can this now be an issue, what do you do when there are no uplift connectors rated/tested for lower SG's. As soon as we start specifying the stronger lumber, which we have all been using per the code for a very long time, we will be the ones dealing with the complaints from the contractors and owners because their structure is more expensive because of this.
How will this be addressed in currently adopted, older codes; or even for projects that are already in construction using older codes but potentially using this inferior imported lumber.
This is IMO another example of code writers being out of touch with the industry and allowing for or pushing for changes to codes that have real world impacts without consideration for all the possibilities of their code change/amendments. Semi-joking - who was paid off for this code update allowing inferior lumber to be imported and used .
RE: Construction Plans: How to Improve Clarity of Framing Lumber Specifications
RE: Construction Plans: How to Improve Clarity of Framing Lumber Specifications
RE: Construction Plans: How to Improve Clarity of Framing Lumber Specifications
Dr. Woeste: no, I don't feel the longer form is very helpful. I do use that for composite lumber to make sure I have adequate LVLs, but a material spec sheet is easy to get for those. I've never received a sawn lumber material data sheet. And as ChorasDen said, it means nothing to anyone in the field. If you're working on a big 5 story wood job with a seasoned contractor, maybe. But most wood builds are far less sophisticated.
The additional specifications are going to end up as more of a CYA note than anything else, I'm afraid.
RE: Construction Plans: How to Improve Clarity of Framing Lumber Specifications
RE: Construction Plans: How to Improve Clarity of Framing Lumber Specifications
As mentioned earlier, another design issue is published fastener and connector adjustments factors for G less than 0.42. While preparing for VT short courses, I reached out to two of the leading fastener and connector manufacturers and they kindly sent the information needed to adjust their tabulated values for the cases of G less than 0.42. You can view the SST adjustment information here: https://ssttoolbox.widen.net/view/pdf/pqvsvpxr5l/C...
and for Connectors here:https://ssttoolbox.widen.net/view/pdf/yf0tka1rqn/L...
RE: Construction Plans: How to Improve Clarity of Framing Lumber Specifications
"...instead of using the typical spec such as this:
"All wall framing lumber shall be 2x4 KD19 No.2 SPF or Btr."
In my experience that isn't the typical spec at all, typically wood is handled in the general structural notes with one note covering the moisture content at installation and a table or list of species/grades by application. "or Better" is almost never utilized as it gives too much freedom to the contractor/supplier and instead "or an approved alternate" is noted.
Perhaps I'm not understanding Table 4G as well, is this table stating that imported lumber can be stamped and sold as if it was the lumber from table 4A through 4E? If that is what is being allowed then I'd say the grading needs to be revised such that the imported lumbers meets or exceeds the North American Species values, lumber with lower properties should never be allowed to ship under the same stamp.
RE: Construction Plans: How to Improve Clarity of Framing Lumber Specifications
Personally, I will not entertain allowing this lumber in my designs or on my projects. I will not change my specifications to include design values. To do so just adds more work for me, and as others have said it doesn't accomplish anything because lumber stamps don't list design values, so there is no way to verify. I will change my specifications to explicitly exclude multi-species combination stamps and any non-North American species stamps.
Interesting that the Structure magazine article sites the last 20 years that this non-North American lumber has been arriving in the U.S. construction market. I first saw these stamps in the wild about 4 years ago, right after... you guessed it... Covid 19. That's when this really became a problem, when the North American lumber mills fell behind due to Covid, and the construction industry turned to overseas imports as a cheap, emergency substitute. Now no one can put the genie back in the bottle.