How do you decide what grade of Southern Pine to use? 1

[SomethingStructural]

What's your typical decision process like for deciding whether to use No. 2, No. 1, Select Structural, etc. when specifying Southern Pine? Obviously less cost is preferable, but higher quality wood will need smaller members. Is it different for every job?

 

[JAE]

Typically in our area No. 2 grades are most available so that determines our choice in most cases.

Check with your lumber supplier and see if they can get you a feel for the range of costs associated with their available grades.

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[SlideRuleEra]

Concur with JAE, the availability of No.2 grades almost always makes the decision for you.

...higher quality wood will need smaller members.

Be careful about relying on that reason. Note that the modulus of elasticity is normally constant for all grades. Even if smaller members are structurally adequate, deflection will be greater for the smaller member. You could wind up with a design that has excessive deflections.

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[SomethingStructural]

Thanks to both of you.

 

[Signious]

If you are specifying studs for external walls, some jurisdictions will allow you to use No.3 grade (stud grade) for vertical studs. I have had a few clients request this by name as a cost saving measure - just make sure you specify top and bottom plates as No.2 minimum.

 

[Ron]

No. 2 can be used in almost all structural applications, including truss chords, studs, conventional framing, etc. Read the grading rules for Southern Pine (Southern Pine Inspection Bureau (SPIB)).....you'll see the differences and the effect.

 

[MacGruber22]

I agree with everyone. You should specify readily available material (No. 2 spruce-pine-fir or southern yellow pine for me in the mid-Atlantic region) as much as possible. If you can't get the No.2 species to work out with your project constraints, a more economical and expedient choice may be an engineered wood product. I specify laminated veneer lumber beams and joists frequently, without much if any complaints from owners or contractors.

"It is imperative Cunth doesn't get his hands on those codes."

 

[boo1]

I would not use SYP for walls, white woods are more stable

 

[MacGruber22]

I would not use SYP for walls, white woods are more stable

Can you elaborate?

"It is imperative Cunth doesn't get his hands on those codes."

 

[boo1]

2x4s and 2x6s from plantation grown southern yellow pine twist and warp. From the grain structure you can see they are from small trees.

Spruce Pine Fir or Hemlock, Douglas Fir woods are more stable.

 

[SomethingStructural]

Do they twist and warp even at service loads?

 

[MacGruber22]

I would imagine that boo1 is referring to shrinkage effects, if this is true. Boo1 - is there a publication out there that has documented this tendency? Or is this just an opinion based on the accumulation of your professional experiences? I can't imagine the SPIB ever admitting to this, if it were true.

"It is imperative Cunth doesn't get his hands on those codes."

 

[SlideRuleEra]

Here is an excerpt from a 1997 Louisiana State University paper, Effects of Elevated & High-Temperature Schedules on Warp in Southern Yellow Pine Lumber. The following passage is from a discussion on the quality of available timber:

"...increasing amounts of lumber are being cut each year from young, small-diameter trees. Unfortunately, this material exhibits a high propensity for warp when it is dried."

Here is a link to the complete paper:

http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/5016/Effects_Elevated_ocr.pdf?sequence

The Southern Pine Inspection Bureau (SPIB) does not address this tendency on their website, however, the Southern Forest Products Association does. In the FAQ section of the website the following question is presented: "Why does lumber sometimes warp and crack?"

Answer, in part: "...Warp is aggravated by irregular or distorted grain and the presence of abnormal types of wood, such as juvenile wood..."

http://www.southernpine.com/faq/

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[Ron]

SYP has a distinct grain structure and is susceptible to the type of rough log sawing used for production lumber to affect its warp and twist characteristics. Old growth timber combined with quarter sawing the log produces very stable lumber. New growth, small diameter timber is usually flat sawn to prevent waste, resulting in the issues boo1 noted.

All of this; however, is considered in the grading of the lumber. Further, the exposure of the lumber in the field and the way it is stored can have a significant effect on the individual boards and their propensity to warp or twist. Cupping is also a common issue, particularly with lumber widths of 6 inches and over. Look at the end grain of the piece. You will usually be able to clear predict its tendency to cup based on the grain. The more curved the grain at the end, the more chance of cupping.

 

[MacGruber22]

All of this; however, is considered in the grading of the lumber.

This is what I would have expected. But, the way I am interpreting boo1's statement is SYP lumber in a given grade tends to warp/twist itself out of the initial grading classification, even in the best of conditions. Maybe the case for selecting a more stable species would be to *try* to mitigate effects from poor material storage onsite, or exposed framing prior to the enclosure of the building with vapor barrier and fenestration.

Would you agree boo1?

"It is imperative Cunth doesn't get his hands on those codes."

 

[dhengr]

BrentStru:
Lumber should normally be dried to a reasonable level for structural use. It should be kept under cover in transit, at the lumber yard, and on the job site, until it is nailed into place. And then, the building should be enclosed as quickly as reasonably possible, to minimize weather damage. Mostly, reasonable cost and local availability pretty much determine the grade of lumber that you normally use. Try not to use different grades of lumber on the same job, except for the obvious differences btwn. primary dimensional lumber and stud grade, because sure as hell the #1 or structural grade will end up being used for blocking and joists and those couple needy beams or headers will end up being made from #2 anyway. When several grades are used, this potential mix-up has to be controlled and managed in some way There has been a real significant deterioration in the quality of lumber being sold over the years of my practice, and we are going to have to get used to using this lower quality lumber being produced today, there just isn’t any old growth timber left to cut any longer. This also ushers in the greater use of manufactured substitutes for solid sawn lumber, which can be designed and manufactures to use the lesser grade raw material more efficiently. While some warping, cupping, etc. is figured into the allowable stresses and design methods, the biggest problem with these conditions might be finishing and installation of sheet rock, siding, cabinetry, windows and doors, etc. The carpenter has to pay special attention to weeding out the real crap and working with the rest. That is, putting all joists in with their crown up, all studs should bow in the same direction, and not too much, etc. And, who has the time or experience for that kinda stuff any longer?

 

[MacGruber22]

BrentStru:
Definitely agree with dhengr on the mixing of grades. You can't rely on the framer to keep track of two different grades; it all looks the same to the untrained eye - hence why it is better to specify one species groups and grade, and then use engineered wood where required. It should follow a similar logic for the engineered wood, e.g. do not mix strengths of particular styles of engineered wood. If you are specifying laminated veneer lumber (LVL), don't specify 1.8E and 2.0E LVL. But, it is common to have a mixed bag of engineered products, i.e. LVL, Parallel Strand Lumber (PSL), Glue Laminated Timber. They are very different in appearance, and can't be easily confused for one another.

"It is imperative Cunth doesn't get his hands on those codes."

 

[Ron]

MG22....grading is done at the mill. The conditions are controlled and the moisture content is reasonably near to 19% for kiln dried lumber. Once shipped, the moisture content can change drastically and will affect the wane, warp and cupping characteristics of the finished lumber. If the lumber was flat sawn, these issues are exacerbated unless the particular board came from the center cut of the log.

Spruce and fir are less susceptible to dimensional anomalies than SYP; however, they also have lower material properties that require structural reconsideration. They are also less dense than SYP and will absorb more moisture, thus being more susceptible to rot.

 

[MacGruber22]

MG22....grading is done at the mill.

Not sure where I mention otherwise.

"It is imperative Cunth doesn't get his hands on those codes."

 

[Ron]

You didn't. I was following on with your interpretation of boo1's comments. I agree. Just trying to be reasonably complete in my answer.