HABIFRAME Storm Shelters-Texas Tech Debris Impact Test

Pretty cool above ground, wood framed residential tornado shelter. 

Kerfing a Bowed Stud

Wood studs are not perfect and never will be.  Neither will any other material, plant, etc. that is made in nature.  Through experience, science, and understanding, we learn how to manipulate natural materials to be suitable for our needs.  Trees, which have branches in many aspects of our lives (pun intended!), are a top renewable resource.  After centuries of harvesting tress, and thus lumber, to build shelters, etc., you would think our understanding of the material would be very thorough.  But as some say, it can be hard to see the forest through the trees.  In other words, sometimes you need to see the big picture.  Below is an example of an instance where the big picture reveals much more than what is in front of you 

It is common for carpenters to kerf a wood stud to remove a bow in the stud to allow for the wall finish to be flat.  Depending on the function of the wall, such as load bearing, the kerf in the stud may be reinforced with a section of 2x material lapped and fastened to the full height stud.  Regardless of how the stud is kerfed, reinforced, etc. the most important piece of knowledge involved is the function of the stud.  Knowing what the stud supports can result in an appropriate repair solution. 

These 2x6 studs have a kerf that leaves just over an inch of solid material. 

Now, back to that forest and tree stuff.  The worker who cut these studs could only see the bowed stud (tree) in front of him.  Had he looked at the big picture (forest), he might have realized that kerfing a first floor stud in a four story building might not be a good idea.  And yes, this wall does carry floor trusses from each floor above. 



Southern Pine: Status Update

Click here for a summary of the current status of the proposed changes to southern pine design values.  I imagine that within the next 5 1/2 months (prior to implementation of new values) there will still be much debating on this issue.  The primary point of concern boils down to this: change the lumber design values or change the lumber grading process.  Timber Products Inspection has stepped up to the plate to develop a revised lumber grading process.  Click here for more information from TPI.  

Southern Pine Span Tables - Proposal

The Southern Forest Products Association (SFPA) is kind of like a customer service department for Southern Pine.  They provide assistance to end users in understanding Southern Pine grading rules and design values while also marketing lumber products.  The SFPA website at http://www.southernpine.com/ provides information for end users regarding green building, pressure treatment, and product applications in addition to providing span tables for joists, rafters, headers and beams. 

The SFPA is closely involved with the Southern Pine Inspection Bureau's (SPIB) proposal of new Southern Pine design values.  While SFPA is not directly involved with testing of lumber or the establishment of design values, they will be the group that helps end users understand and adapt to any changes in Southern Pine use.  The SFPA has published a sample span table for joists and rafters based on the proposed design values.  You can find the tables here. 

USDA Study of the Environmental Benefits of Wood

The USDA recently released a study of the science of the environmental benefits of using wood and wood products in construction.  In a previous post here, I wrote about the USDA's decision to support wood construction.  This recent study is a continuation of the USDA's path to officially supporting wood construction for public entity structures. 

USDA Report

Comments from SFI

Q&A with the President of AISC

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. 

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