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Question for those who are well versed in framing and then maybe some code as well. I got into a discussion the other day between a couple other trades, they were suggesting I was wasting my time using treated plates in all of the basement walls I built.

The basement is a 4" slab of concrete. It's not a leaky basement, but I figured since the wall plate is directly touching the concrete floor, that it should be treated. I also went an extra step and used foam sill sealer.

Am I going too far with this? Is it just a waste of money? Treated plates are significantly heavier, more expensive, and also annoying to work with because they warp a day after picking them. I'm considering going to common kiln dried lumber and using the foam sill sealer then, but I worry that if the basement ever floods that sill plate will wick up water so fast, and destroy the drywall and studs until vented and dried out.

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In my state the bottom plate is required to have the foam seal and treated lumber for external load bearing walls only. I do use foam internally but not treated lumber. The foam prevents moisture from wicking into the plate and rotting it. I do use the foam inside but more often I will use tarpaper as I usually have a roll and it works well and is cheaper than sill seal foam. What you are doing will last but is a bit over the top (one of my buddies says I am over the top with the tar paper). In the case of a flood, the Sheetrock itself is going to wick the water faster than the wood will. I like the barrier under the plate be it foam or tarpaper.

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I've been involved directly and indirectly with home construction since the 1980s. Here in Minnesota, bottom plates, window bucks, sill plates, and anything else in direct contact with concrete (or even separated by foam "sill seal") have been pressure-treated by code and convention for decades.

You're right that warpage is a problem. Keep the treated stuff under a layer of sheathing with weight on top of it until the day of use. Use fasteners rated for the particular chemical used in treatment (stainless or galvanized). No big deal.

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  • Glad to hear that you guys up there are required to do what I'm doing then. I know it may be over the top but that is what I'd rather be known for. I do believe the foam sill seal product would prevent the need for treated bottom plates. Maybe on the next basement I'll go that route. Building Inspector was okay with that method. I like to order my plates very last, and then screw them together every 4' into one or more to help resist the warping, and unscrew as needed. That has been my latest tip. And yes, keeping out of the sunlight! And yes, always using galvies or ceramic torx. – Nic Sep 20 at 3:04
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Your basement doesn't leak.

Today.

I've had two houses with leaky basements. This is sufficient that my working rule is that "All basements flood. Someday."

The price differential for putting a PT sill plate is is small, and it means that it won't mildew as badly if you get the typical 1/8 to 1/2" 'the laundry drain backed up' flood.

If you are paranoid like this, also set all your drywall 1/2" above the floor, then attach all the baseboards 1/8" above the floor. This will allow better vacuuming the water up when the day arrives.

For the same reason, I don't put W2W carpet in the basement. Painted concrete is fine, thank you. Might consider glue down vinyl tiles.

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I've worked on a number of basements in the Midwest and have never used treated plates or foam sealer. None were external load bearing walls, just interior walls with a two foot space between them for access and storage. Treated lumber needs to dry out and that's hard to do in a basement. If the basement floods, whatever you put down will suck up water and destroy drywall. Just my humble experience. Good luck.

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    Treated lumber doesn't need to dry out. In fact, it shouldn't until it's secured in place or it tends to warp badly. The issue isn't flooding, but constant exposure to moisture due to simple wicking. – isherwood Sep 19 at 13:46
  • @isherwood Is treated and pressure treated the same??? – JACK Sep 19 at 15:55
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    Yes. I know of no other means of treatment used for modern construction lumber. – isherwood Sep 19 at 17:35
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Treated lumber contains toxic chemicals and using it for indoor framing is a violation of building code in most areas.

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  • Not true at all. We've been using treated bottom plates in basements for decades here in Minnesota, mandated by code. Sill plates and window bucks, also. – isherwood Sep 19 at 13:43
  • Same here in Oregon it is required on external walls. – Ed Beal Sep 19 at 14:00
  • Jim, today's modern treated wood is much safer. At least that's word on the street. It can be used for garden beds even without worry. It is still a common belief that you don't want to inhale the sawdust from treated lumber. But I think sawdust in general is bad for our lungs. But anyways, treated wood is required here for sill plates before floor joists, and that is considered indoors and has been for years. – Nic Sep 20 at 3:00

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