PT lumber when there is contact with concrete

miamicuse

I have always gone by the rule of using PT lumber for framing or furring when there is concrete on one side.

I now have a bathroom shower where two sides are concrete exterior walls (which I have used PT furrings), and one side is an interior wall with standard 2x4 studs.

I will be attaching cement board over the three sides of the shower before tiling.

The question is, the one side where I have standard 2x4 studded wall, can I hang the cement board directly over it?

If I did that, aren't those non-PT stud faces coming into contact with concrete (cement board)?

Do I need to furr out this studded wall with PT furring just because of this?

joecaption

Simple ansewer is no. It's fine to use untreated againt tile board.

miamicuse

Joe, thank you.

What would be the reason that it's not required? Is it because the cement board is going to be dry and normal concrete block walls or floors may have moisture?

Blondesense

Bingo! Just make sure it is properly waterproofed.

GBrackins

the reason according to the 2009 International Residential Code .....

SECTION R317 PROTECTION OF WOOD AND WOOD BASED PRODUCTS AGAINST DECAY

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 (457 mm) or wood girders when closer than 12 inches (305 mm) 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 (203 mm) 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 (12.7 mm) on tops, sides and ends. 5. Wood siding, sheathing and wall framing on the exterior of a building having a clearance of less than 6 inches (152 mm) from the ground or less than 2 inches (51 mm) measured vertically from concrete steps, porch slabs, patio slabs, and similar horizontal surfaces exposed to the weather. 6. Wood structural members supporting moisture-permeable floors or roofs that are exposed to the weather, such as concrete or masonry slabs, unless separated from such floors or roofs by an impervious moisture barrier. 7. Wood furring strips or other wood framing members attached directly to the interior of exterior masonry walls or concrete walls below grade except where an approved vapor retarder is applied between the wall and the furring strips or framing members.no mention or requirement for cement board attached to studs

Good luck!

__________________
Gary

"You get what you pay for, and sometimes free costs more!"

brockhouse

Just make sure you waterproof the walls and floor in you shower before you tile. If you keep the board from getting wet then the studs probably won’t be able to get wet. It's also good if you use either 2x8 or 2x10 blocks and block between the studs at the bottom of the wall which will help further prevent water from getting past the board. Make sure when you tile a shower you tile the floor before the walls and make sure you are using the right thinset for the job trio flex is for floors servo lite is for walls. Make sure that there are no grout lines that have holes which will lead to a potential leak. If you wanted I have also seen a product called Curdi Board used on the floor and walls in your shower however it is a lot easier to install then cement board. Use Silicone caulking to waterproof around faucets leaving a 1/4" space at the bottom of the faucet which will allow any moisture that does get into the wall through the faucet to dry.