"Jambe, post: 185496, member: 17827"]Just for the sake of discussion, what would be required for a sill plate on a concrete foundation wall to not have to be pressure treated? (Think untreated Timberstrand plate. Strandguard is getting difficult to obtain.)
What could be placed between the concrete and the untreated plate to make it acceptable?
R317.1 does not permit an impervious moisture barrier between the sill plate and foundation wall in lieu of preservative treated or naturally durable wood.
The exception is for sills and sleepers on slabs. This manner of construction is prescriptively done with a "6-mil polyethylene or approved vapor retarder placed between the concrete floor slab and the base course or the prepared subgrade where no base course exists" in accordance with R506.2.3. The same applies to monolithic slabs for the footing (at which the rebar can no longer serve as a UFER!)
The alternative for foundation walls is if the sill is at least 8-inches from the exposed ground. I believe you would be hard pressed to find an impervious moisture barrier that is approved directly under sills for this purpose. Additionally we may often see some sort of rubber or bitumen material under the ends of girders, it is not prescribed nor an alternative is provided if the clearance is less in item 4.
R317.1 Location required. Protection of wood and wood based products from decay shall be provided in the following locations by the use of naturally durable wood or wood that is preservative-treated in accordance with AWPA U1 for the species, product, preservative and end use. Preservatives shall be listed in Section 4 of AWPA U1.
1. Wood joists or the bottom of a wood structural floor when closer than 18 inches or wood girders when closer than 12 inches to the exposed ground in crawl spaces or unexcavated area located within the periphery of the building foundation.
2. All wood framing members that rest on concrete or masonry exterior foundation walls and are less than 8 inches from the exposed ground.
3. Sills and sleepers on a concrete or masonry slab that is in direct contact with the ground unless separated from such slab by an impervious moisture barrier.
4. The ends of wood girders entering exterior masonry or concrete walls having clearances of less than 1/2 inch on tops, sides and ends.