Monday, October 31, 2011

Southern Pine Design Values: Comments

Now that some of the dust has settled after ALSC's decision to postpone its ruling on proposed southern pine design values, the debate can begin with all sides in the mix.  While the debate continues about the need for new design values, what does the industry do in the mean time to protect itself from inadequate design?  An engineer from Florida recently asked me this question and it definitely bears some consideration.  An edited version of my response is as follows: 
At this time, I am not sure how I will design wood while waiting on the possible new design values.  There are several issues to consider before making this decision.   

First, I have yet to see the actual proposed new design values.  While I do not doubt the testing, I would like to see the test data.  Researchers at Mississippi State have conducted some tests that show a decrease in lumber strength but not enough to justify the amount of design value reduction proposed by SPIB.  

Second, while the proposed new values cover each size of southern pine, only 2x4's have been tested.  I do not think we can assume a correlation between the design values of each size based on the In-Grade testing performed 20 years ago.  Too much has changed in the timber industry.  

I think the easiest thing to do is limit the stress ratio of members we design to maybe 0.80 instead of 1.0.  This would be easier than trying to adjust design values at this time and it may not make a significant difference in the overall design.  
This was a short and quick answer to a complex problem.  I have two new wood projects on my desk, including a multi-story apartment building, that will give me a chance to create and implement solutions for ensuring an appropriate design.  I will post about my findings in the next few weeks as I complete the projects. 

Also, I have requested a copy of the SPIB proposal.  The recent comments from the SLMA has a link to request the proposal for those who are interested.   

Another good commentary regarding the industry's stance (or lack thereof) on what to do between now and January 5th when the ALSC rules on the design changes is here

Friday, October 28, 2011

Southern Pine Design Values: Updates

While it may be difficult to navigate the different sources of information regarding the proposed southern pine design values, one source I have found continually provides excellent coverage.  Just remember that the coverage is from the perspective of a group that does have a stake in the outcome. 

SBCA Lumber News

I would also like to add that I receive weekly emails from SBCA regarding news that affects the lumber industry as a whole.  I recommend anyone with an interest in the lumber and housing market to sign up for the emails.

SBCA Magazine News

Thursday, October 20, 2011

Southern Pine Design Values: Update

According to a memo sent out by the American Lumber Standards Committee, the Board of Review has postponed making a decision regarding the SPIB's proposed changes to Southern Pine design values for 60 days. This postponement is to allow interested parties to review and comment on the technical aspects of SPIB's proposal. See the link below for the memo. ALSC Memo

Tuesday, October 18, 2011

Southern Pine Design Values

As some of you may already be aware, on October 20th, 2011 the Southern Pine Inspection Bureau will be proposing new allowable design values for southern pine lumber to the Board of Review of the American Lumber Standard Committee.  The proposal will lower design values for all grades and sizes of visually graded southern pine by approximately 25-30%.  This will have a major impact on all aspects of the lumber industry. 

While the testing for these changes began in 2010, it appears as though many groups have only recently become aware of the proposed changes.  One point of contention for many industry representatives is the limited sample size of testing performed to provide the basis for the changes.  To my knowledge, approximately 400 southern pine #2 2x4 were tested.  No other sizes or grades were tested.  Further contention lies in the lack of collaboration with other industry groups to insure that everyone affected has a chance to aid in the process of determining the new design values. 

Much more information can be found in the following links:

SBCA News Page

Southern Pine Inspection Bureau Updates

Anthony Forest Products News Page

Another Note:  While there appear to be several written items about the changes, I have not found a table of the proposed design values to compare with the current design values.