Pressure treated wood

Toxic fumes as the treatment dries and evaporates. Same reason you shouldn't burn your old fence in your fireplace.

So they can sell more RVs... I agree for so little more all kinds of problems could be decreased. Arsenic has not been in PT for 10 years... you can burn the new stuff but the ash is a problem so not recommended.
Pine is what's usually pressure treated so it's heavier and stronger than the fir/spruce often used.

PT wood is a lot heavier too.

ab257 wrote:
PT wood is a lot heavier too.

I retired in 1999 so new information is not what I have but it was always wet when I cut it.

chevman

Modern PT wood chemicals are highly corrosive to aluminum (and some other metals, but particularly aluminum), which is used a good bit in RV construction. It would not be nice to have your outside siding dissolve away in a couple of years.

I don't know that house wrap would help things much; the usual route for water intrusion is not through the side of the wall, but through openings and seams where the hose wrap wouldn't seal. It might help to keep any moisture that got in within the shell of the RV, which would be a detriment.

I would guess that RV's aren't supposed to have the "possibility of water intrusion".

Better materials avail. All alum. for example. Ford for example got away from wood and went to steel and then got away from steel and went to alum. Some makes use plastic in their RVs.

and I believe treated wood requires special material screws.

Fuggedaboutit. Ain't ever gonna happen.

It would be very difficult to build an RV with pressure treated wood if not impossible. It's use and installation methods is a specialty field in itself. It's use is much more expensive. It would be a total nightmare...

Any and all fasteners MUST be compatible with PT lumber and wood. This means either galvanized fasteners, stainless steel, polymer coated, and I think a couple of others. Aluminum cannot be in direct contact nor can non-coated steel be. The type and use of the correct compatible fasteners is dependent on the moisture content of PT wood and lumber. If the correct fasteners and other things (brackets, for example) aren't used, they'll corrode in no time.

Back in 2003, the chemical that was being used was chromated copper arsenate (CCA) and was changed to amine copper quat (ACQ) and copper azole (CA) and supposedly some other copper-based chemicals for toxicity reasons. CCA wasn't banned but it's use is now more for industrial and marine applications like pilings and below grade foundations. Copper is generally considered safe but it's the arsenic in CCA that is a concern for health. Here is what the EPA has to say about CCA EPA and pesticides.Around this part of the world, ACQ is what is available in lumber yards.

When working with PT wood, special procedures and precautions must be used. For example, wear a mask, collect all sawdust and send it in bags to the local dump, do not burn it and wash clothes separately after being in contact.

In building construction, the use of PT products, fasteners and anything else related to it is strictly controlled by various codes and standards. In the RV industry, codes and standards are almost non-existent and there are no governing bodies to monitor them and their use. As it is, they can't even get many ordinary straightforward things done right.

In RVs, moisture may not be from intrusion, but can be from moisture buildup inside in cold weather and inadequate ventilation. If wood, moisture and rot are a concern, then aluminum framing is an option, except there will still be a plywood (or OSB) sub-flooring and roof decking. Maybe marine grade plywood would be a good thing for them to use.

Keep the water out, and it's a moot point. Roof maintenance and caulking go a long way to avoiding the need in the first place.