Fastener reasoning for treated material 2

[jayrod12]

Good Morning All,

Got a question for all of you. Why are all fasteners into treated lumber required to be galvanized or stainless besides the moisture aspect? Do the chemicals used to treat the lumber cause problems for standard nails/screws?

I've never had a need to know why I've just always specified hot-dipped galvanized or stainless nails and it's never been a problem until now. We have been retained to help certify some pwf foundations that were constructed incorrectly (yes foundations not a singular foundation, 8 duplexes). It hasn't been confirmed yet what kind of fasteners were used for the foundations but it appears as though common wire nails were used and then blue skin was applied over the nails.

If the fastener requirement is strictly because if you need treated lumber it is probably moisture susceptible or are there other factors in play?

 

[JAE]

Treated lumber now uses different chemicals than previous years when arsenic based treatments were used.

The newer chemicals are much more aggressively damaging to ferrous materials like nails. As a result, better coatings on the nails (or stainless) are required.

Simpson Strong-Tie has some general verbiage on this found here and on adjoining pages to this link.

 

[jayrod12]

Thanks a bunch!

 

[msquared48]

http://www.cctia.org/FAQ_Files/10.014_Metal_Fasteners_with_Wood.html

Mike McCann
MMC Engineering

 

[dhengr]

Jayrod12:
These foundations are likely old enough so that the lumber and plywood used the older CCA-C treatment, about 10 years or older. I believe that the CCA-C treatment and higher retention rates are still available for some applications. They are just not sold to the general public, at big box stores, so they may be tough to find. For wood foundations the retention rate had to be .6, and special fasteners have always been required. The rationale from the beginning was primarily that the lumber and fasteners could be subjected to water/moisture over time, so common nails were not sufficient. Although, the issue of the treated lumber played a part too, but not to the extent the problem exists with today’s preservative treatments. But, using the wrong fasteners has been a common problem with inexperienced designers and builders. The waterproofing details and foundation drainage details were also critical details and were often done poorly or inadequately. Once water got into the walls it was very slow to dry, so you could have constant moisture conditions on the fasteners.

I’d pull some nails/fasteners and take some samples of the plywood and lumber, have them tested and verify what they are. Look for some particularly distressed areas, inside the bldgs. and do some investigating there. Open up the wall from the inside and look for water stains, moisture in bldg. mat’ls., any mat’l. deterioration or damage. Dig around outside and check the waterproofing integrity. Connections btwn. the studs and the top pls. and then to the fl. diaphragms are often deficient and have moved under loading. Wall corners or changes in direction are often deficient, improperly nailed and blocked.

Be careful while working on the exterior of the foundation. Some years ago I was sitting on my haunches, you know, my butt on my heels, 6-8" off the ground; watching a couple workers doing the excavation as we studied the waterproof details. Things were going just fine, except for the quality of the details and workmanship, when all of a sudden, the automatic sprinkling system went on, and to my surprise I was sitting on an outside bidet.

 

[JAE]

dhengr - I'm not sure why you say these are "old enough". The original post indicates or implies that they are recently constructed...or did I miss something?

 

[jayrod12]

Brand spanking new.

They were constructed before we were brought into the project. Now we're left to clean up the mess.

And they already got approved for temporary occupancy so people are living in these things during what appears to be a bunch of repair work.