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RE: CBC 2304.11.2.2 - 8-inch Clearance from exposed earth to wood framing members including wood sheathing.

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Obtaining a variance is not an acceptable solution because of the amount of time it will take to receive the necessary approvals. The owner is under a time constraint and would rather pay more for PT framing or if the solution I came up with is agreeable, would consider doing what the city required with the compromise of using a Wolmanized material wither PSL or PT Douglas Fir as a spacer to separate the taller concrete stem where the garage is being added from contact with the existing 2x4 w/ plywood sheathed walls. If done this way, the remainder of the framing on the higher concrete stem can be all conventional lumber with the exception of the PT mud-sill.




From: Jordan Truesdell, PE [mailto:seaint2(--nospam--at)]
Sent: Thursday, February 07, 2008 6:58 AM
To: seaint(--nospam--at)
Subject: Re: CBC 2304.11.2.2 - 8-inch Clearance from exposed earth to wood framing members including wood sheathing.


Well, the first thing I would do is write a 2 paragraph letter to the AHJ asking for a variance to accommodate the existing  conditions.

Second, while PSLs are theoretically available in preservative treated (Wolmanized(R), I believe), I've never actually used them. I've never heard of timberstrand in PT.  I'm not aware of any preservative treated OSB, but you can get PT plywood.


Dennis Wish wrote:

For some reason I seem to get bounced off the list a few times a year and for the last several months have not had time to subscribe once again to start receiving e-mail.


The California Building Code section 2304.11.2.2 requires that the top of the finished slab on grade and / or the top of the foundation wall where a mudsill is connected is to be a minimum of 8-inches above finished grade. Historically, this was changed from 6-inch clearance to 8-inches. I’ve not real problem with the code on this as in our area termite damage is the primary rationale behind this section of the code. However, I had a small remodel come in today that only required an engineer to design the non-compliant portion which in this case was the roof beams that cannot be done by conventional or prescriptive codes. I agreed to help him by addressing only the non-compliant section requiring engineering as the rest conforms with prescriptive methods.


One of his other corrections had to do with the height of the foundation wall of a new garage he is adding. It must be two inches higher than the adjacent 6-inch clearance for top of slab/foundation wall and finished grade. The code goes on to say that “Alternately, wood shall be of naturally durable or preservative-treated wood.”


Even if he chooses to use a 3x mudsill, the additional clearance will barely be adequate to provide nailing clearance for the sheathing at the boundary of the panel against the sole plate. One alternative is re-grade the property which is a major project for this client. The second choice since this is a floating sloped slab in the garage is that only the ends of the foundation walls bearing the stud wall framing will need to be raised the additional 2-inches.


Does anyone know if we can rip a 4x pressure treated piece of lumber to secure against the exposed existing wood framing to create a separation between the extended new 2-inches of concrete from coming in contact with the non-pressure treated lumber and then lay the new garage wall PT mudsill over the ripped block to start the garage wall framing?


The second option is to use Timberstrand or PSL lumber to frame the walls and a structural sheathing rated to be “durable” (whatever this means) or preservative treated? Does anyone know if Trus-Joist Timberstrand or PSL lumber used for wall framing will satisfy this requirement as durable or preservative-treated wood? If it does, will OSB satisfy the same requirement for structural sheathing or is there a recommendation of an APA rated panels that will comply as “durable and/or preservative-treated” lumber?


New construction is not an issue, but satisfying an addition to an existing structure poses some new challenges that I have not considered before.




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