Metal Fasteners and Pressure Treated Lumber

[Glenn9643]

I've got a project underway and need to know more about the corrosion effects of the new pressure treated lumber on the fasteners that I would normally use.
I've been a big fan of steel joist hangers for years, and adapt them to many jobs. My experience with them has shown that they add a lot of strength to many applications. Now, with the new pressure treated lumber, I'm unsure. The joist hangers, hurricane clips, and other metal fastener gizmo's at Lowes/HDepot don't appear to be galvanized to me, and certainly aren't stainless. Does anyone know if it would be worthwhile to place 15lb felt between the joist hangers and the treated wood surface? Seems to me that's about the best solution, since they don't have stainless or galvanized gizmo's for my needs?

 

[_RaT_]

Read this:
Simpson Strong Tie

 

[SWB]

I am building a house and my contractor told me the code won't allow them to put galvanized metal next to the treated lumber like they use to because of the corrosion properties of the new treated lumber. They had to put a layer of plastic flashing next to the treated lumber or between the treated lumber and any metal it came in contact with.

 

[Freds]

This is interesting. I knew there was a new treated lumber, but I didn't know it was more corrosive to metal. Regardless of the metal you want to place next to the lumber or any plastic flashing or felt paper inbetween.... what type of fasteners are you allowed to use now that will penetrate the lumber? It doesn't seem like it would do any good to isolate the metal from the lumber and then use a regular nail or screw /forums/images/graemlins/confused.gif

 

[Bird]

Freds, I don't understand the technical stuff like some of our members do, but I built a small porch and steps for my daughter about 3 years ago, and then another set of mobil home steps about 2.5 years ago using treated lumber. The first project was lumber from Lowe's and the second was lumber from Home Depot. I used all screws, no nails, and both stores have screws labelled for treated lumber and screws labelled for cedar, etc. I'm not sure what the difference is. For the porch, I did use some joist hangers, but I didn't try to insulate them from the wood. Everything is still solid so far but I haven't gotten under there to look at the joist hangers since we built that porch.

 

[Freds]

It seems that if they make fasteners specifically for treated lumber, they should also make metal components specifically for treated lumber. I guess this is what this post is about.

 

[Bird]

I agree that they should, and maybe they do. I don't recall seeing any specifically for treated lumber but don't know whether such exists or not.

 

[_RaT_]

They do. In my earlier post I linked to Simpson, the company that makes most of the fasterners out here, explains that it depends on what the many treating plants across the country use as the formula for their preservative. It also depends on the application such as indoors or outdoors, dry, wet, etc. They make hot dipped galvanized, they have a coating called ZMAX I think it is and finally they have stainless steel in two different types of stainless. The fasteners are also available in a variety of metals and coatings. Places like Home Depot/Lowes can probably order it for you.

 

[pilonidal]

Put up my deck 2 yrs ago just after the new treated lumber was coming out. I have a homebuilding magazine with a good article on it. They took the arsenic out of the wood and increased the copper content...alot, that is why it is more expensive now. You are supposed to use copper flashing now between the house and the wood/ledger. Use triple zinc hangers and nails. Lowes has them, and stainless screws if you want. The regular deck screws will suffice though with there coating. I burnt some scrap treated, I know your not suppose to, it left a nice green area in the ashes from all the copper left behind.

 

[2nstonge]

Simpson ZMAX hardware, triple galvanized fasteners & stainless are all rated for direct contact with the new ACQ pressure treated wood. Screw boxes say right on them "approved for ACQ applications" or some such thing. You could put a piece of felt (or self-stick rubber roofing membrane) between the Simpson hardware and the PT if you wanted to but it's not necessary. Besides, you're going to drive a fastener thru it that will be in contact with the hardware and the wood - and there's no way to insulate the fastener from the wood. The screws are expensive, whatever you do, don't go cheap and use sheetrock screws!

There was a time when the ACQ first came out that stores had a mix of hardware for the old PT and new stuff and some people (including builders) got screwed up and used the wrong fasteners. Doesn't hurt to double check the packaging.

-Norm