I'm sure this issue has been discussed somewhere in this forum, but I could not find any info on it.
Anyway, seems most people use treated bucks, or they use some type of barrier between untreated bucks, as well as treated sill plates, and I am no different. As I type I am reading section R319 from the IRC. It states that "treated lumber be used if all wood framing members that rest on concrete or masonry exterior foundation walls AND are less than 8 inches from the exposed ground". With that said, why does the majority use treated for windows above grade, as well as sill plates. (where icf goes to the eve). I believe good practice would be to isolate any type of wood from the concrete with some type of membrane, but treated lumber is very expensive as well as very unstable!. Just curious to hear what others think or come across with this issue.

Thks......Bunt

A good question. I wonder how present metal components, that come in contact with PT wood, will stand up to corrosion over time. I do see a benefit from insects in warmer areas of the country.

Since I'm not familiar with codes earlier than 2006 IRC I don't know if it used to be required by the code or not. I've gotten the impression it was. And as you know, all people, including builders, can get set in their ways and don't want always to change. Also, I wonder how many builders really read the code in detail. In fact, just two days ago the estimator at the lumber yard still thought you had to use PT any time the wood was in contact with concrete. The 2006 IRC requirement was news to him.

When I brought up this exact issue with the BI for my house he said, "Hmmm, I'll have to check and call you back." A couple of hours later he called and said, "You're right. If you're more than 8" above ground you don't need decay resistant wood. But a moisture barrier would be a good idea." My civil engineer cousin also said a moisture barrier is a good idea because of the differences in thermal properties of wood and concrete and condensation can form in the interface, rotting the wood.

So the only place I'm using PT is the bottom plate of the 2 x 4 pony walls in the crawl space. I maybe wouldn't even absolutely need them there because I plan to bring the vapor barrier over the pony wall footers. But why risk a hassle w/ the BI over a few dollars?

As for cost, the material quotes I've gotten show 2 x 12 STR & Better Doug Fir to be pennies less per lineal foot than 2 x 6 PT s***!

Well, it sounds like there are many contractors out there who are not familiar with the details of the IRC. I'll bet I could ask 10 contractors if treated lumber was required when in contact with concrete and 9 of them would say yes, not aware that many of the times treated is not required. Unfortunately I believe many inspectors are unaware of this as well, including an inspector where I am building right now,.......had ta show him where it was in the code.

...Bunt

What material would be a good moisture barrier between the untreated wood and concrete that is more than 8" above the ground? On remodels I have seen that roofing felt does not last. Would a sill sealer between the wood and concrete last for the life of the home?

I've used peel'n stick waterproofing,......that seems to work well.

.Bunt

I was planning on using roofing felt around my window and door bucks. Are you suggesting that may not be so good? Has the deteriorated felt you've seen been between wood and concrete, or like under siding? What I've seen under roofing has been good 20+ years after install.

Maybe I'll do as my civil engineer cousin suggested, emulsified asphalt smeared on the backside of the bucks. Emulsified is OK against foam, I understand. Solvent based is what we don't want to use w/ foam.

Sill sealer would probably work but all I've seen is 4" wide versions of it. Poly sheeting might be the best and cheapest.

Use 8" or 6" sill sealer, it will expand as your lumber shrinks over time.

Dave

I used 1/2" foam board on the outside of my door/window bucks. I cut the foam board in 8" strips which is the inside width of blocks that I used. I attached the foam to the center of the bucks and stacked the blocks around it. This way the concrete never touches the wood and the bucks are also insulated from the concrete.

Cory

Is there some reason that structural plastic lumber can't be used in this application?  Its not suppose to shrink and it doesn't rot.  It seems that this could be used in alot of application in constructing a home.  www.american-plasticlumber.com/structural

Can't? Probably no particular reason it can't be used. Isn't? Based on what I see with plastic trim one big reason it isn't, $$$$$$. For instance, V-buck for 6" ICF runs around $4.50 a lineal foot. 2 X 12 doug fir structural, about $1.00 per lineal foot. That's why I'm using 2 x 6 for window bucks & 2 x 12 for door bucks.