Pressure Treated ok from sub floor down?
Hello All...i understand there will be some shrinkage ect. But is PT lumber, including; seal,band, joist, beam & plywood subfloor ok to build with?...Are there any codes that say no...no. Are there any adverse affects for using PT in these areas?...Will termites munch on PT?...Will mold/fungus attack PT as quick as it will standard lumber?...
thanks in advance....paul
Such materials usually must be implemeted when in direct contact with concrete...
And within at least 8" of grade....
Or in direct contact with water...among other locations.
PT lumber, among other types of naturally rot and insect rsistant lumbers such as decay-resistant heartwood of redwood; black locust; or cedars..shall be acceptable.
Tell us which state and which county and we may be able to indicate what code regulations actually apply...
PT should be just fine and probably prudent to use given your location.
Your local codes may also allow for rot and insect species like locally harvested cypress to be used as well.
From what I understand of the codes, it (PT) is not to be used on floors of interior living space levels (as in the walls).
Other than that, the only thing I would recommend NOT DOING is:
Don't put it in as a subfloor (PT Plywood) . Use regular floor sheathing. There is too much shrinkage to be used as a proper subfloor base, no matter what kind of material you plan on installing for your finished floor, carpet, tile, wood floors; You WILL have problems if you use it there.
Treat Lumber is OK and Required
International Residential Code, Florida's Code, requires treated floors, joists, sills, and girders whenever these structures come directly in contact with slabs on grade, within 18" over exposed soil in a crawlspace, and whenever wall framing comes within 6" of exterior grade.
Studs or furring strips placed in direct contact with exterior masonry walls shall also be treated.
Section R319.1 Flordia Residential Code 2004 states:
"R319.1 Location required.
In areas subject to decay damage as established by Table R301.2(1) , the following locations shall require the use of an approved species and grade of lumber, pressure treated in accordance with AWPA C1, C2, C3, C4, C9, C15, C18, C22, C23, C24, C28, C31, C33, P1, P2 and P3, or decay-resistant heartwood of redwood, black locust, or cedars.
1. Wood joists or the bottom of a wood structural floor when closer than 18 inches (457 mm) or wood girders when closer than 12 inches (305 mm) to the exposed ground in crawl spaces or unexcavated area located within the periphery of the building foundation.
2. All wood framing members that rest on concrete or masonry exterior foundation walls and are less than 8 inches (203 mm) from the exposed ground.
3. Sills and sleepers on a concrete or masonry slab that is in direct contact with the ground unless separated from such slab by an impervious moisture barrier.
4. The ends of wood girders entering exterior masonry or concrete walls having clearances of less than 0.5 inch (12.7 mm) on tops, sides and ends.
5. Wood siding, sheathing and wall framing on the exterior of a building having a clearance of less than 6 inches (152 mm) from the ground.
6. Wood structural members supporting moisture-permeable floors or roofs that are exposed to the weather, such as concrete or masonry slabs, unless separated from such floors or roofs by an impervious moisture barrier.
7. Wood furring strips or other wood framing members attached directly to the interior of exterior masonry walls or concrete walls below grade except where an approved vapor retarder is applied between the wall and the furring strips or framing members."
You can access Florida Codes online here:
There is no code prohibiting the use of treated lumber on the interior of any structure.
While it is true that non-kiln dried treated lumber can have expansion and contraction problems from moisture as it dries, this can be alleviated by using kiln-dried-after-treatment lumber which has the same moisture content as that of standard framing lumber (15-19%), and is just as stable.
What I meant by 'floors' was: as in Living space Floors, not actual physical floors themselves, I was referring to: 'in the walls'. Living-area walls
According to MA State Building Code: Under 780 CMR 2311.0 NATURALLY DURABLE AND PRESERVATIVE-TREATED WOOD.
2311.3.2 - Where wood that is pressure treated with water-borne preservative is used in enclosed locations where drying service cannot readily occur, such wood shall be at a moisture content of 19 percent OR LESS before being covered with insulation, interior wall finish, floor covering or other material.
So, in effect, YES there is a code that does not allow Treated Wood to be used in an interior wall if it does not meet the approved Moisture Content Level. This is very important in the construction schedule of 'closing up interior areas'.
Because moisture content can be hard to verify and very few contractors carry an accurate moisture meter, Inspectors in these parts WILL NOT allow improperly dried PT to be used on any interior walls. So, it is generally not allowed when it is unnecessary and there is no definite function for it being installed in that location of an enclosed interior wall(s).
That has been our experience with our local building inspectors.
Regarding floors: Same issue. I have seen some really screwed up finished flooring because it was installed on PT . Plywood that was not completely allowed to dry out.
So, if there is no definite function for it to be PT, I definitely recommend against it in sub floors.
Other than that, the residential codes are pretty much all the same as to areas where Treated wood (PT) must be used.
Under the IRC this 19% or less moisture content lumber is called kiln-dried-after-treatment lumber and is perfectly acceptable to be used in structural sheathing, subflooring, or framing.
But the Massachusetts code prohibiting the use of treated lumber with moisture content of 19% or less is apparantly peculiar only to Massachusetts and is not found in national model codes.
It's still a 'good practice' to use nothing but kiln-dried treated lumber in a home, but as for the national model codes like the IRC, nothing prohibits the use of treated lumber with contents more than 19% from being used in the structure of a building.
For Florida IRC 2003 Code and the original poster's application, either kiln-dried treated or non-kiln dried treated would meet code and be acceptable regardless of the moisture content.
And Florida Code, as in all other jurisdications where the IRC applies, still requires treated lumber framing and sheathing in the locations cited in my previous post.
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