Ground Contact Lumber

[XR250]

I am working on a deck job where the inspector claims that ground contact PT lumber (0.4 lb/ft^3 ACQ) should have been used in this case (see attached pic) in lieu of standard PT lumber (0.25 lb/ft^3 ACQ. I guess he feels that water will get trapped in there causing continuous contact with fresh water. What are your thoughts?

Thanks in advance.

 

[SlideRuleEra]

I agree with the inspector. The success of pressure treatment of lumber is variable since each member has its own individual characteristics. The consequences of deterioration of the framing members shown will be major repairs, not just the replacement of a bad board. This is technically not "ground contact", but IMHO, it is equivalent.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[XR250]

Just found out that the inspector is considering this "embedded" in the concrete which is his reasoning for the GC PT - as code requires this.
The concrete was cured for a week before the joists were installed.

 

[a2mfk]

What about sliding a moisture barrier between the wood and concrete? I would do this even if it were not required. Building paper is cheap. Like Sliderule said, rot damage is not cheap...

 

[XR250]

Good idea - although i doubt building paper will survive very long. Maybe some peel and stick

 

[a2mfk]

I was thinking 30lb roll roofing in my head but typed building paper. Go as robust as you can fit in there.

This is a nice little article on the subject from Simpson, but it is geared towards protecting steel connectors from the PT chemicals, not moisture protection of wood.

http://www.strongtie.com/ftp/bulletins/T-PTBARRIER08-R.pdf

 

[boo1]

could you slip a stainless steel or galv shim in there to seperate them?

 

[XR250]

I think what we are going to do is sister a 3 ft. long ground contact rated joist to the side of the existing - centered over the concrete. That way if the original bearing rots, we still have support.

 

[dik]

EPDM sheet material?

Dik

 

[msquared48]

Just use petrified wood as the contact material.

I definitely would try to get some plate steel between the wood and concrete. A Simpson standoff connector would have been much better to use here rather than the detail used. But that is hindsight. Just do not use this detail in the future. Use a metal connector with a bearing plate.

Mike McCann
MMC Engineering

 

[Splitrings]

We use neoprene. NDS makes reference to corrosion at a steel wood interface.