Pressure Treated Bottom Plates Inside Steel Building

[BentBierz]

Good day, all! I am getting ready to frame the inside of a steel building addition I made to my shop so that I can put up T&G plywood walls. I have had the floor sealed with polyaspartic so no bottom plates will have direct contact with bare concrete.

Given that there won’t be contact with concrete, I am curious if I should still use PT bottom plates or would untreated suffice. In either case, I plan to put down sill foam since I have rolls of it left over from framing out my shop several years ago.

Through all my research about using PT I have found very mixed opinions on letting it 1) dry before installing it —to— 2) installing it wet to keep it from warping like crazy while it is drying out. My inclination is to just use untreated bottom plates since all the walls will be interior and will be in a climate-controlled building but thought it was worth asking. Thank you for any replies.

 

[finn]

Use the PT material for the sills.

My shop was built using untreated spf material for sills, and there are a few soft spots After maybe 20 years Snow melt accumulates around the heated slab, and water must seep through the framing near the man doors.

The alternative would be to lay a course of block or three to get the sill away from the ground. That’s what we did when building the 32x54 garage at about the same time the shop was built, per the inspector’s recommendation. No rot evident in the garage sills.

 

[BentBierz]

Use the PT material for the sills.

My shop was built using untreated spf material for sills, and there are a few soft spots After maybe 20 years Snow melt accumulates around the heated slab, and water must seep through the framing near the man doors.

The alternative would be to lay a course of block or three to get the sill away from the ground. That’s what we did when building the 32x54 garage at about the same time the shop was built, per the inspector’s recommendation. No rot evident in the garage sills.

Thanks for the reply Finn. One thing I don’t have to worry about in my part of Texas is snow in the shop! I am a Northerner at heart and miss cold weather and snow (don’t miss shoveling it though). Any thoughts on when to install the PT…still wet from the big box store or let it dry out some?

 

[PCustoms]

Install it wet

 

[MoonRise]

Concrete (or masonry) touching the ground is considered 'wet', even if coated.

And the sill will be on the floor, in a shop, so might get wet or damp from spills or whatever.

Also, ground level so reduce the chance of termites or ants-with-hardhats (carpenter ants) from munching on the sill plates.

Use the PT.

Note that if using PT, you MUST use the correctly coated fasteners. All (or most/many) of the PT chemicals are really-really corrosive to metals. Inside/indoors you might not have quite as fast of a corrosion problem as outdoors, but you still NEED to use the proper material coatings on ANY metal that touches the PT.

And do NOT put aluminum (flashing, brackets, termite shield, etc) in contact with PT lumber. Most of the 'new' PT ( new as in anything newer than CCA, which has not been available for general use/purchase for maybe 20 years now) has higher levels of copper than the 'old' CCA chemical mix and wreaks absolute havoc on aluminum.

Installing the PT sills when 'wet' (and I've seen them so wet that they almost drip or splash when hit with a hammer when driving a nail) isn't really going to stop them all that much from warping or twisting. I'd rather deal with dry(er) stuff and just not use any really banana'd ****.

 

[BentBierz]

Concrete (or masonry) touching the ground is considered 'wet', even if coated.

And the sill will be on the floor, in a shop, so might get wet or damp from spills or whatever.

Also, ground level so reduce the chance of termites or ants-with-hardhats (carpenter ants) from munching on the sill plates.

Use the PT.

Note that if using PT, you MUST use the correctly coated fasteners. All (or most/many) of the PT chemicals are really-really corrosive to metals. Inside/indoors you might not have quite as fast of a corrosion problem as outdoors, but you still NEED to use the proper material coatings on ANY metal that touches the PT.

And do NOT put aluminum (flashing, brackets, termite shield, etc) in contact with PT lumber. Most of the 'new' PT ( new as in anything newer than CCA, which has not been available for general use/purchase for maybe 20 years now) has higher levels of copper than the 'old' CCA chemical mix and wreaks absolute havoc on aluminum.

Installing the PT sills when 'wet' (and I've seen them so wet that they almost drip or splash when hit with a hammer when driving a nail) isn't really going to stop them all that much from warping or twisting. I'd rather deal with dry(er) stuff and just not use any really banana'd ****.

Thanks…it's been a while since I looked at PT at Home Depot or McCoy’s but the last time I had to get a few boards that section of the store (Home Depot in particular) looked like a rainforest. Might have to expand my search to see if I can find a little drier PT.

"ants-with-hardhats (carpenter ants)”…I will have to admit I have never heard that term before but that is funny as hell!

 

[340RedCoupe]

Don’t buy any wood from HD if you can avoid it, it’s junk. Go to a real lumberyard, at least around here (Cleveland, OH) its cheaper and the quality is miles ahead of HD.

 

[egdede]

In my neck of the woods HD only sells treated lumber rated for outside use. It's brown. The real lumberyard also has green treated which is safe for indoor use.

 

[LopezBart]

Given that there won’t be contact with concrete, I am curious if I should still use PT bottom plates or would untreated suffice. In either case, I plan to put down sill foam since I have rolls of it left over from framing out my shop several years ago.

If you're within 8" of the ground you must use PT. Taller foundation walls w/ an impervious seal between the concrete and wood can avoid the PT. PT wouldn't hurt, however....

 

[nadogail]

I have found that the “Green Stuff, copper wood preservative” to be fairly effective in controlling termites.

 

[Mick56]

Since you may have termites in your area, after framing but before you finish off the inside, you could spray some Boracare on all the studs up 12" or so.

 

[mike93lx]

If it touches concrete, I always use PT. Wet stuff from HD is fine.

I have bought lots of lumber at both yards and big box stores and the only time the yards are better is when I buy a higher grade. #2 is #2 anywhere, but a yard might have #1. Waste of money for framing, though.

If you have easy access to KDAT (kiln dried PT), that can be nicer to work with as it's lighter

 

[BentBierz]

If it touches concrete, I always use PT. Wet stuff from HD is fine.

I have bought lots of lumber at both yards and big box stores and the only time the yards are better is when I buy a higher grade. #2 is #2 anywhere, but a yard might have #1. Waste of money for framing, though.

If you have easy access to KDAT (kiln dried PT), that can be nicer to work with as it's lighter

Thanks. I’ll have to see if I can find KDAT…that might be the ticket for my situation.

 

[BentBierz]

If you're within 8" of the ground you must use PT. Taller foundation walls w/ an impervious seal between the concrete and wood can avoid the PT. PT wouldn't hurt, however....

Think I am going to just hedge my bet and put down PT and along with sill foam I already have.

 

[BentBierz]

Since you may have termites in your area, after framing but before you finish off the inside, you could spray some Boracare on all the studs up 12" or so.

My property is surrounded by woods and we definitely have termites. Fortunately, in the 9 years we have lived here, we haven’t seen any in our house or the interior walls of our two steel buildings…knock on wood (pun intended)!

 

[scofo]

Not a response to your question but, I had a Mccoy's open up closer to home lately. Its so much easier to go in with a list and let the yard guys load it instead of loading it twice at the box stores. Thats if you can find enough through the culls at the box store. The yard guys wont throw true **** on your trailer if you're helping or standing there. Dimensional lumber is cheaper or same at M's too.

I had a BMC that was pretty sweet but the last time I went in looking for UC4B type treated wood the guy behind the CS desk kinda indicated they were only interested in servicing homebuilders and didnt have it anyway, oh well. UC4B is damn near impossible to find in the ATX area. Maybe not a problem for Alvin as its coastal IMO.

 

[gearhead1]

I used PT for the bottom plate when I built mine. I had 2 rows of block and still went with the PT (and sill foam). There was some warpage due to some time lapse from the time I bought the 2x8 bottom plates until using them. Once the walls and sheathing is on, the weight will take care of the bottom warpage.

I also used PT for the vertical boards that finish the opening for the garage doors. They are covered with aluminum, when the siding went on. That way anything that is on the ‘bottom’ surface that could get wet is PT and more rot resistance just in case. It was worth the extra cost for the ‘additional insurance’ so to speak, in my mind.

I’d rather be a little particular on the front end, than have to deal with issues later.

In your case, I would still do PT with sill foam if it was me. What if there was a water leak, a spill, etc. It’s extra protection for not that much more money in the grand scheme of things.

 

[Hooked]

My property is surrounded by woods and we definitely have termites. Fortunately, in the 9 years we have lived here, we haven’t seen any in our house or the interior walls of our two steel buildings…knock on wood (pun intended)!

Couple things: 1- there's an 84 Lumber in Alvin (528 and 35 bypass area) which may have dried PT lumber. 2- termites, I'd suggest having termite treatment around your home regardless if you've seen any or not. If you see them you already considerable damage. If you decide to have it done shoot me a message and I'll give you the contact info for the fella we use (no relation but a good guy).

 

[Joemctag]

Concrete (or masonry) touching the ground is considered 'wet', even if coated.

And the sill will be on the floor, in a shop, so might get wet or damp from spills or whatever.

Also, ground level so reduce the chance of termites or ants-with-hardhats (carpenter ants) from munching on the sill plates.

Use the PT.

Note that if using PT, you MUST use the correctly coated fasteners. All (or most/many) of the PT chemicals are really-really corrosive to metals. Inside/indoors you might not have quite as fast of a corrosion problem as outdoors, but you still NEED to use the proper material coatings on ANY metal that touches the PT.

And do NOT put aluminum (flashing, brackets, termite shield, etc) in contact with PT lumber. Most of the 'new' PT ( new as in anything newer than CCA, which has not been available for general use/purchase for maybe 20 years now) has higher levels of copper than the 'old' CCA chemical mix and wreaks absolute havoc on aluminum.

Installing the PT sills when 'wet' (and I've seen them so wet that they almost drip or splash when hit with a hammer when driving a nail) isn't really going to stop them all that much from warping or twisting. I'd rather deal with dry(er) stuff and just not use any really banana'd ****.

Agree. Use P.T. with HOT-DIPPED, stainless or those screws that say they’re for pressure-treated lumber. The new pt, last 20 years or so has copper and will eat up regular plated fasteners. If you’ve taken screws out of an old deck, you’ll know. If you’ve got metal , like siding, what I do is use the 4” wide peel-and-stick rolls, cut narrower, to cover the pt wood where the metal will be against it. Good luck!