Corroding AC2 Fasteners

[Joseph Stevens]

It is a well known fact that the newer ACQ or AC2 pressure treated lumber will corrode the average galvanized deck nail and hangers.

My question is, is this corrosion a problem when builders are nailing the pressure treated sill to the wall framing (like on a slab on grade foundation). I am assuming that the builders just pop in whatever standard nails are in their paslode at the time. Are the builders required to use a special type of nail/screw or is this corrosion only a problem on decks and outdoor structures that see water regularly.

Thank you.

[Michael Thomas]

When I choose to fight this battle, I report this one in considerable detail specifically to avoid push-back from builders:

Observation: The wood sill plates (in location) and treated with ACQ preservative are attached to structural members above them with fasteners not recommended by manufacturers of ACQ treated lumber for use except in "dry, indoor" locations.

Analysis: Wet or damp ACQ lumber will rapidly deteriorate "convention" fasteners such as nails and screws. When when such fasteners fail structural integrity is lost, and structural problems can result. Special corrosion-resistant fasteners must be used in such locations.

For example, according to Universal Forest Products, one of the largest producers of ACQ treated lumber (bold and underline mine):

"When ACQ preserved wood is used for interior applications with continuous dry conditions, where the wood in service will remain below 19% equilibrium moisture content, the performance of fasteners, hardware and other metal products in contact with the treated wood should be similar to that experienced with untreated wood."

- http://www.ufpi.com/literature/acqfastener-216.pdf (http://www.ufpi.com/literature/acqfastener-216.pdf)

Thus, "conventional" fasteners are suitable for use with ACQ treated lumber only in continuously dry interior locations.

The reason wood sill plates are required to be treated to prevent rot is that they can be expected to be exposed to higher moisture levels than structural members higher above grade. Their fasteners will be exposed to the same conditions, therefor in my opinion only fasteners recommended by their manufacturer fro use with ACQ lumber in exterior applications should be used to fasten treated sill plates to other structural members.

Recommendation: If the seller or their agent cannot demonstrate that the manufacturer of the sill plate material approves the use of conversational fasteners in this location, have a qualified and insured contractor secure all structural members to the sill plate with fasteners recommended by their manufacturer for use in ACQ treated wood in wet or damp locations, and in accordance with current national standards and local code requirements.

[Stuart Brooks]

It is a well known fact that the newer ACQ or AC2 pressure treated lumber will corrode the average galvanized deck nail and hangers.

My question is, is this corrosion a problem when builders are nailing the pressure treated sill to the wall framing (like on a slab on grade foundation). I am assuming that the builders just pop in whatever standard nails are in their paslode at the time. Are the builders required to use a special type of nail/screw or is this corrosion only a problem on decks and outdoor structures that see water regularly.

Thank you.

How about the ACQ plates fastened to the concrete floor in a basement? I see case-hardened nails, shot-pins, and concrete screws. Are they ACQ rated, probably not. Also, how about ACQ framing for windows and doors in a basement wall? - almost always good ole cut nails.

[Michael Thomas]

How about the ACQ plates fastened to the concrete floor in a basement? I see case-hardened nails, shot-pins, and concrete screws. Are they ACQ rated, probably not. Also, how about ACQ framing for windows and doors in a basement wall? - almost always good ole cut nails.

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[Stuart Brooks]

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BLUE-TAP Con crete Screws - Case Hardened Masonry Anchors - Florida Fasteners Direct - Factory Direct Discounts Toll Free: 877-803-6151 Concrete Anchors, Hurricane Fasteners and Other Fasteners (http://www.blue-tap.com/blue-tap.html)

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Thanks Michael. At least they are made but are they being used? One has to depend upon the person doing the work to 1) know there is a difference 2) Actually buy the correct fastener, 3) care enough to to it right. I think that unless we can tell for sure one way or the other we should not needlessly scare a client. But it is food for thought and what may evolve in the future.