Pressure treated wood inside building 1

If the deck is "waterproof", slopes at 1/4" per foot and is well vented, you might be able to get away with non PT joists where you live.

Personally though, living in the Northwest with all the mold and rot problems, I would use the PT in spite of the chemicals. If there is that much of a problem with chemical sensitivity for the resident, then you should consider columns at the exterior of the deck and a ledger at the rimjoist.

Mike McCann
McCann Engineering

For the common "outdoor" wood preservatives your concerns are valid (even though the "worst" one, CCA, in no longer readily available for residential use), see "Human Health Hazards, Treated Wood Products" at this link:

However, there is a possible compromise. Consider using wood treated with borate compounds, they are not weather resistant, but using msquared48's approach they should perform adequately and are muchs less toxic. See "Alternatives to Chromated Copper Arsenate (CCA)
for Residential Construction" at this link:

SlideRuleEra, great website! Thanks! Now just get currently published documents on there (don't get caught) and we will be set.

As for using pressure treated lumber indoors. We often spec it to brace horizontally cracked residential foundations. We recommend they insulate, vapour barrier, and seal it, as you would normally. Based on our findings, the chemicals don't go into the air unless the treated material is submerged in water which releases the chemical, and then evaporates. I'm not sure to what extent the chemicals would have to evaporate to be harmful. But I can tell you that pressure treated lumber is used indoors EVERYWHERE.

Has any one found anything else scientific on this topic. I think that wisconsin goverment website sliderule posted is irrelavent. Thats more of a government covering its butt document.

i was just laughing to myself...."treated lumber is used indoors everywhere".

I suppose so are cigarettes!

JrStructuralEng - Want vindication for putting treated lumber indoors... here you go:

Want to see which way regulatory agencies and "public opinion" that establish "rules and laws" leaning... look at the links here:
and

There are many types of treated lumber, for example creosote was one of the first proven carcinogens. Frankly, I don't have a (technical) problem with CCA or currently available "outdoor" preservatives being used indoors if they are totally encapsulated with sheetrock, paneling, flooring, etc. However, like so many other issues, the long-term effect of this type of chemical on young children is just beginning to be scientifically researched. IMHO, it is now (politically) very foolish to specify typical "outdoor" treated wood for use indoors.

Of course, this is just an opinion... perhaps you can offer some backup for your strongly stated opinions.

I have almost twenty years of experience in the wood industry and would have no problem with the use of AQC or CCA treated wood indoors.

Personally I thin CCA is one of the safest and most effective treating products available.

Regarding Borates I don't have enough experience to comment on that, although the firm I work for has used them in some applications where a beam is partially indoors and partial outdoors.

If the material you are dealing with is Penta, you might have some off gassing concerns. I would be surprised however if you have floor joists that have been treated with Penta.

Check out the Permapost website . Under the custom treatment tab, there's a list of wood preservatives available. Each treatment includes the MSDS and a brief description of its uses. The Hi-Clear II treatment (it contains permetherin, wierd) is what you may be looking for. You just need to let it air out for a couple of weeks before installation. The mineral spirits need time to offgas.

Slide rule, don't take my OPINIONS personally.

Those people that establish the "rules and laws" that you refer too. Can they be trusted? I have a feeling that they will send us all into the asbestos mines for 30+ years before anything is regulated.

See the problem is, there are a crapload of pressure treated wood basements built in North America. And even though we want to believe these agencies and goverments are saints, they won't condem these buildings until they are damn sure they arn't safe. And don't think the two arn't inter-related. It only becomes an unsafe product when public opinion affects political standing. And even if they are damn sure, they probably still will bury the issue. The problem is all treated basements have been built to the national building code, all based on regulating agencies & recommendations.

Going back to the original post, I wouldn't recommend using PT material for joists. For basement walls, I think your fine.

JrStructuralEng - Thanks for the clarification, I had not considered existing treated wood basements as a typical application for treated wood indoors. That is an excellent example of your term "everywhere". Where I live basements of any kind are few and far between because the water table is typically less than one foot below ground level - I don't see them often.

There are so many products that were used "everywhere" at one time that have been taken off the market, examples are:

1. Lead Paint
2. Asbestos, which you mentioned
3. DDT
4. Urea-Formaldehyde Foam Insulation (UFFI)

Just because something is in common use now does not mean that it will or should be in the future.

It is very possible that some treated wood products used for indoor applications could be next.

I never condone cantilevered decks on houses. Eventually, water will leach in through the joists at the interface with the outside walls. Also, you will get a large amount of shrinkage in the pressure treated joists that could affect interior finishes such as tile on the floors. I also recommend at least a 4" step down from the house onto any exterior decks to help prevent water infiltration at the door sills leading onto the deck.