Wood Framing - Top Plate Material 1

[zlindauer]

I am doing residential framing design in the Austin, Texas area. I have a client who would like to build stud walls with utility grade lumber at the top plate. He has pointed out to me that several engineers in my area allow this. I have tried to verify that this is acceptable with an engineering calculation, but have not been able to prove that it works, especially since I assume one of the plates is spliced. I also have not been able to find a code reference that requires the plates to be #2.

Does anyone here allow top plates in stud walls to be built with #3 or utility grade lumber?

Thanks.

 

[mike20793]

Yes, if the studs are directly placed beneath the supported joists/trusses.

 

[atrizzy]

The top plates serve to primarily provide a tension/compression diaphragm chord and transfer the joist load above onto the studs. If you calculate that stud grade lumber satisfies that criteria for your loads, there shouldn't be an issue.

If you're designing a taller building, shrinkage and moisture content would become a concern in the horizontally oriented plates.

 

[zlindauer]

The studs will not necessarily align with the rafters and joists.

The primary concern I have is weak axis bending of the plate between the supporting studs.

 

[KootK]

This comes up often here with regard to plate capacity (not utility grade specific). Search the term "top plate" here and several exhaustive threads will manifest themselves. Folks have tried complex things with modelling continuity, considering random splice locations, accounting for sheathing support, etc. Long story short: it doesn't work real well by the numbers without the alignment but, still, nothing seems to go awry in practice.

A lower grade of material just worsens the problem, to the extent that there is one.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[BSVBD]

zlindauer... To support your primary concern, here in Wisconsin, with snow loads, unbalanced snow loads, and the ever-increasing truss spans, nearly 20 years ago, I've forced our main General contractor to use SPF #2 (or better) triple top-plates to support the 24" o.c. trusses between the 16" o.c. studs. On occasion, I've specified a DFL #2 bearing plate on CMU to support the high Fc... primarily a different situation.

Contrary to my typical tendency and practice over being allegedly "over" conservative, I have never considered the splice location(s). As Koot stated, nothing "seems" to go awry in practice. I suppose that the splice may "survive" our concern by becoming a naturally transformed participant of a successful 8" diaphragmatic cantilever. My explanation is a stretch, but, in my opinion, there is often the occurrence of a mysterious, inconclusive, successful load-path that I am often content to accept.

 

[JoelTXCive]

In Houston, many production builders will use #3 utility grade lumber for top plates with studs under all the splices.

How nice of a house is it? The sheetrocker that has to attach sheetrock to that top plate, so when you get large regions of bark or 'rounded edges' it will make the top of the wall wavy.

 

[CANPRO]

Even if you could show on paper that it was acceptable, my question to the contractor would be - why bother? What are the savings in switching just the top plate for a lower grade? A few cents a foot of wall? With the lower grade you'll probably end up tossing out a few 16ft lengths that are too crooked or banged up to use anyway - so there goes your savings. There are better ways to save a few dollars on a project.

 

[atrizzy]

CANPRO, the devil's advocate position that the contractor may suggest would be to repeat the question to you: 'Why bother?' ... if it's not needed, why use #2?

 

[XR250]

I think around here anything longer than 10' is #2. I have actually never considered the top plate grade.

 

[jayrod12]

Our notes state that the plate materials must meet or exceed the grade of the studs. That being said, I've never spec'd lower than a #2 stud unless it was a storage shed.

 

[zlindauer]

Thanks to everyone for replying.

One last detail: The contractor is asking for forgiveness, not permission. They've already built several houses with #3 plates and got called out by a city inspector.