Tag Archives: lumber grading rules

Smartphone App to Test Lumber Strength

I have been a proponent of machine rated lumber since I bought my first truckload to be made into trusses at Coeur d’Alene Truss (http://www.cdabuilders.com/) back in 1978. Years later I spent five terms on the Board of Directors of the Machine Stress Rated Lumber Producers Council (http://www.msrlumber.org/).

I have opined previously on the merits on machine graded lumber: https://www.hansenpolebuildings.com/2012/12/machine-graded-lumber/.

Mississippi State University™ has taken lumber testing technologies and placed them directly into the hands of the public. Please read on in this MSU article:

The “Smart Thumper” app, available for download in the Apple Store, uses sound waves or vibrations to determine stiffness, a quality that relates to strength, for individual pieces of lumber. (Photo by David Ammon)

STARKVILLE, Miss.—Determining the stiffest piece of lumber is now easier with a new smartphone app created by scientists in Mississippi State University’s Forest and Wildlife Research Center. 

Called “Smart Thumper,” the app uses sound waves or vibrations to determine stiffness, a quality that relates to strength, for individual pieces of lumber.  

Developer Dan Seale, professor in MSU’s Department of Sustainable Bioproducts, said it will help carpenters, contractors, architects, engineers, lumber mill personnel and consumers. He pointed out that it can be particularly beneficial for the do-it-yourself market.

The Mississippi State team that has developed an app to determine stiffness of individual pieces of lumber include, from left, Frederico Franca, assistant research professor of sustainable bioproducts; Songyi “May” Han, an MSU sustainable bioproducts doctoral student; and professor Dan Seale. The team’s work is part of the university’s Forest and Wildlife Research Center. (Photo by David Ammon)

“All lumber is not the same, even though it may be graded the same. The grade is based on a range of values and characteristics,” Seale said. “Perhaps a consumer has a pack of lumber which meets the specification for No. 2 grade, but they need a couple of pieces for a header, something that might span the opening for a window or door. This app helps select the stiffest pieces that are least likely to sag over time,” Seale explained.

Frederico Franca, the app’s co-developer and an assistant research professor in sustainable bioproducts, first envisioned the app when he discovered that the equipment designed to test lumber costs around $84,000.

“The goal was to make something cheaper and more readily available to give consumers and stakeholders broader access to nondestructive testing equipment,” Franca said. “Now anyone with a smartphone can download the app to help pick out the stiffest pieces for whatever they are building.”

His love of physics, along with the desire to create something less expensive, fueled his idea for a smartphone app that would render lumber values through the use of sound and vibration. 

“With this app, I can show you which lumber pieces are stiffer and therefore stronger,” Franca explained. “This can’t always be done through visual inspection. You need vibration or you need sound.”

Lumber mills use both visual and mechanical means to grade all types of dimensional lumber. Pieces can be tested for strength and stiffness, and the numbers are crunched through an algorithm to determine grade.

“This app can help further evaluate lumber within established grades, potentially optimizing the longevity and cost efficiency of wood structures by selecting stiffer pieces for situations that demand higher performance,” Franca said.

Also a part of the code development team is Songyi “May” Han, an MSU sustainable bioproducts doctoral student whose 2017 master’s thesis relates to marketing the smartphone app.

The app is available for download in the Apple Store. Visit https://itunes.apple.com/us/app/smart-thumber/id1436858557?mt=8.

Learn more by visiting http://smartthumper.fwrc.msstate.edu/.

Termites and Pole Barns

A Buggy Situation

A client writes to Justine (the Hansen Pole Buildings’ Order Fulfillment goddess) this week:

termites“I was hoping to get some advice.  I’m still working on the building having just completed rafter placement and was starting to pull apart the two bundles of lumber for the purlins.  When I started pulling boards out of the bundle I noticed some surface damage that just kept getting worse as I sent through the stack of lumber.  Toward the center there was a large amount of termites, see pictures.  The odd thing was it only affected the stack of 2X6X10′ boards, the other bundle of lumber, sitting right next to it was untouched.  This is really unusual for our area where summers are hot 90-100° with very low humidity <15-20% making termites a very rare issue.  The lumber was stored as instructed in your manual but now we have a probably 1/2 of the 2X6X10′ boards that are damaged significantly.  Since termites are not a large problem in this area and all of the infestation was in the center of a stack of very wet wood (not from any rain or external water) and there was no damage to the stack sitting next to it, I suspect it came with termites but of course I can’t prove that so as disappointed as I am let me get on to the request for advice.  These boards are primarily used for the purlins and horizontal siding support around the outside of the building.  I know the purlins are structural and need to be 100% clean wood, but is some level of damage acceptable for the horizontal boards between the posts?  If so, how much, or is any penetration by the termites into the wood render it unusable? “ 

Personally, I feel bad for the client, however he did take delivery of the materials back in April and on May 3 he wrote to Justine:

“I have all of the material and all is in good shape.  Thank you for all of your support”

On one hand client has received everything in good order, on the other hand nearly four months later there are some challenges. It is possible the lumber was shipped buggy – wildly random things do happen. It is also possible the material got wet in the spring and the heat from the 90-100 degree summer days caused the relative humidity in the center of the unit to increase as the unit was likely paper wrapped. In either case, it ended up as the perfect breeding ground for pesky little critters.

The lumber grading rules are fairly generous about allowable defects, so some of the damaged materials may be able to be used.

Here was Justine’s response (spot on by the way):

lumber damage“We would happy to provide some advice for this situation. Let me first say this is why we stress so much to inspect and inventory wood as they arrive up front. You are probably correct in your conclusion they came with the mites in the bundle. If the bundle would have been opened then we could have probably avoided your current situation.

To answer your question, yes there are some level of acceptable defects in lumber. Keep in mind the wall girts are just as crucial as the roof purlins in supporting the loads of your building.

You can read about these allowable lumber defects on our blog: https://www.hansenpolebuildings.com/2013/12/lumber-defects/


I would generally apply some common sense on how I use certain boards and which ones I decide not to use. I would say first take the boards you deem usable but in the worst shape in locations which don’t provide as much structural value like in blocking locations. For girts and purlins they don’t need to be perfect but anything meeting the allowable defect rules it will work for those locations but I would try to keep the better boards for those two locations. Anything which does not meet the minimum requirements will have to be replaced.”

Moral of the story – regardless of whom you buy your building from, or where the lumber came from, inspect it thoroughly at time of delivery for defects as well as surprises. This allows for anything out of the ordinary to be taken care of promptly, before feelings get hurt. And, always try to use materials as expediently as possible, the sooner they become part of your new post frame building, the happier they will be.

Part IV: Lumber Quality

We Don’t Always Do Things Perfect, But We Do Listen Part IV

Last summer Hansen Pole Buildings Supplied a pole building kit package to a client who experienced a few challenges and took the time to address them.

Here is the last portion of the email I was responding to (the past three days’ blogs dealt with his items #1-5):
“On the design flaws, and other issues, here is what I have experienced.

6-Lumber Quality

WaneI know you sub this out as well but I was appalled.  The 2X6’s I picked up from Home Depot to finish the job were 10 times better than the stuff I received with my kit.  I had 2X6’s with BARK still attached to them.  I had to use some of them for scrap to cut up because there was not enough edge to screw anything to, on either side!!!”

My response: The “Allowable Defects” section of Chapter 3 of the Construction Manual address your lumber quality concerns. Excerpted from it:

  • Wane – up to 2/3 thickness and 1/2 width for 1/4 length.   An example would be on a 12’ long 2×6, wane could be 2-3/4” on wide face, 1” in depth across 1-1/2” face and 3’ in length.

In the event you received lumber which was outside of the defects allowed within the lumber grading rules, our office would certainly have arranged to have had them replaced at no charge to you. This is why we insist clients inspect and report damages within 48 hours, to give adequate time for replacing any lumber which does not meet standards. We rarely get this complaint about lumber quality, but you can be sure our lumber buyer, Justine, will be having a discussion with this particular lumber supplier. We don’t expect every stick of lumber to be perfect, but we do expect ALL of it to meet lumber quality grade standards….and then some. Once again, we can’t fix what we don’t know is a problem, until “after the fact”.
“7-Delivery Timing

I will preface this by saying that I was not ready for construction by the time all my materials arrived, which was a good thing.  If I was counting on delivery to build in a timely manner I would have been in trouble.  The last thing to arrive, almost 3 weeks after everything else had been delivered, was the hardware needed to attach the trusses.  If I was on a timeline, and not building by myself (literally), I would have been stuck waiting on fasteners and nails.  (Those 20D nails might be a bit much for some of that Kiln Dried lumber as well)”

My response: Our goal is to have materials arrive before they are needed. As such some suppliers will deliver early, especially if it minimizes their transportation costs. This helps to keep the price of your (and any other) building kit as reasonable as possible. As our warehouse controls shipments we make (such as your hardware), the schedule for delivery of your fasteners and nails was timed to coincide fairly closely to the arrival of the specially ordered and manufactured glu-laminated columns.

Folks tend to forget this is an online internet sale. If you purchase from other vendors on-line, (such as Amazon.com) I doubt you can specify when you want things delivered.   We do really strive to deliver things in an organized sequence: construction manual, plans, lumber & hardware, doors and windows, steel roofing and siding. And all within a 2 week “target”. Justine, our materials coordinator, works diligently at this. But even she can only do so much when the actual manufacturing, loading and delivering are outside of her direct control.

From Chapter 11 of the Construction Manual: Pre-drill 20d nail holes to avoid splitting.

As our youngest daughter would say, “Comments, questions or credit cards”! Either of the first two will always be appreciated as well as responded to, the last one is what gets used when people go off on their own without following the building plans, Construction Manual, or asking for assistance. We offer free technical support, and answer questions 7 days a week by email.

It’s apparent this client had several challenges along the way, most of which were not reported until his building was completed. We expect our clients to get a top quality building, at a fair price, each and every time. I started with pole buildings/trusses several decades ago. I continue to be in this business because every single day I am excited to solve people’s problems – with a building that fits their needs, and one I’d be proud to own myself. Someday I want to do a tour of all the buildings I have been involved in over the years. I’d like to be met at every client’s door with a smile, a handshake, and possibly an invitation to sit down and have a beer…and not a shotgun.

Allowable Lumber Defects

As a teenager I worked for Blaine Johnston Construction in the Spokane Valley twice, the summer after my freshman year of college, and again after I was out of school. The second time around, I was the “change order guy” – if a client wanted something changed on their house, I got to go do it.

One particular house had been framed by my Uncle Vern and his crew. Uncle Vern had told me about this 1×12 the guy in the house next door to the site had shown him. When I got sent out to move a window, I took a few moments to introduce myself and ask about the 1×12.

Now what could be so interesting about a 1×12? He had this board in his basement for about 50 years. It was 20 feet long, and perfect….not a knot or other defect in it, perfectly straight grained.

Well, we cut down the last of those trees, 80 years ago, so now we get to deal with lumber defects.

Lumber defects are allowable. Just like people are not perfect, neither is lumber.

Lumber DefectsWood is an organic material. While produced in a “factory” environment (a sawmill), lumber is subject to naturally occurring defects, which are accounted for in the grading rules. These characteristics are taken into account in the allowable strength values for design.

Lumber used in trusses falls into this same discussion. Truss lumber is chosen for strength characteristics, not due to “pretty looks”.  If the expectation is the trusses were to be built from clear, vertical grain, knot and wane- free lumber, a severe disappointment is going to occur. Lumber “appearance” is NOT a reason to reject any truss.

All dimensional framing lumber used in Hansen Buildings is at least graded as #2 (or “standard”) or better.  For discussion’s sake, we will limit the scope to this grade. Four inch and smaller (e.g. 4×6 and any two inch – 2×3 through 2×12 are all graded as what is known as “joists and planks”. The characteristics listed below are not intended to be all-inclusive, but merely to be a frequently seen item overview.

In any given lumber “production run” typically 5% is allowed to be outside grading rules (to have more defects than expressly allowed) and still have the sum total declared as “on grade”.

  • Checks – seasoning checks are not limited. Through checks at ends are limited as splits. Splits can be equal to 1-1/2 times board face width (e.g. 8-1/4” on a 2×6, 16-7/8” on a 2×12). Keep in mind, many times these boards will be trimmed off, especially when used as purlins or rafters.  A split portion may thus be removed when trimmed to be put into service.
  • Knots – on a 2×6, up to 1-7/8” at wide face edge, 2-7/8” at wide face centerline; on a 2×12 up to 3-3/4” at wide face edge, 4-3/4” at wide face centerline.
  • Holes – (from any cause) on a 2×6 1-1/2”; on a 2×12, 3”.
  • Wane – up to 2/3 thickness and 1/2 width for 1/4 length.   An example would be on a 12’ long 2×6, wane could be 2-3/4” on wide face, 1” in depth across 1-1/2” face and 3’ in length.
  • Bow (or Crook) – is a board size and length function. As an example: for a 2x6x12’ – 5/8” is acceptable, with greater amounts allowable with longer lengths.
  • Twist – for a 4x6x16’ would be allowable up to 1-1/2” and still be within grade.

5” x 5” and larger are graded as “Posts and Timbers” and have their own characteristics. Again, addressing #2 grade, they include:

End splits – up to twice the post face are permitted: (Ex: 12” on a 6” face.)

  • Wane – 1/3 of any face.

Bow, crook and twist are NOT limiting factors under the grading rules for posts and timbers.

Incidental damage from material handling equipment which does not adversely affect the lumber greater than the allowable defects listed above, would not be a reasonable cause to reject it.

Being realistic in one’s expectations, makes life go much smoother when it comes to the use of structural lumber. By accepting the fact that “defects happen”, and working with them, makes for a much happier finished product.