Fasteners for treated lumber - decks and outdoor structures

[DHill]

In the process of building my deck I learned that a lot of the fasteners aren't designed for use with the treated lumber beause the copper-based solution introduces a galvanic couple with the fasteners and accelerates their demise. Seems like a big oversight on the part of fastener manufacturers to not respond to this problem sooner.

Simpson Strong Tie recommends hot dipped galvanized fasteners yet right on the shelf at Lowes next to their decking connectors they are selling a box of mechanically galvanized structural screws. The mechanically galvanized fasteners are just tumbled in zinc and the adhesion isn't as strong.

In any case the zinc doesn't stand a chance against wet treated lumber. Simpson Strong Tie also recommends that you don't use stainless fasteners with their galvanized steel connectors because that creates a galvanic couple as well and can turn the connector into the anode.

So there isn't any real answer, though I would guess that the stainless screw + galvanized SST is a lesser evil than zinc plated screws in treated lumber. In the end I used Grip Rite epoxy coated screws (green) because they are supposedly rated for treated lumber in outdoor conditions.




Any experience anyone else can share?

A bit more on how I addressed some of those issues:
http://davionhill.blogspot.com/2012/...rs-can-be.html

[Rockhead261]

Hot dipped is the way to go.

BTW, you should toenail the joists to the ledger and wrap the joist hanger around them. This ensures the height is uniform.

Good tips here

[Mk1Racer]

What 'big oversight'? Hot-dipped galvanized nails have been around for years.

[Egilbe]

What 'big oversight'? Hot-dipped galvanized nails have been around for years.

Most hangers aren't used in pressure treated lumber.

[Mk1Racer]

Most hangers aren't used in pressure treated lumber.

I understand this, but I still don't understand what the supposed 'big oversight' is. HDG versions of common nails have been around for years. I used to sell all kinds of Simpson hangers. Most are spec'd w/ a 16d common nail as a fastener, w/ other nail sizes listed as alternates, w/ a reduction in load capacity. The most common alternate that I've seen used w/ standard joist hangers in outdoor deck construction are 10dx1.5" HDG nails, often referred to as TECO nails. IIRC, when using TECO nails w/ Simpson hangers, you reduce the load capacity by ~35%. You still need the full-size 16d common nail for the shear nails. Although many will just use 10d common nails for the shear nails, as that's what is used for most of the general framing.

To the OP, IIRC, drywall-style screws, coated or not, are not listed as approved fasteners for Simpson hangers. I believe any approved screw-type fastener has to have a flanged head and be of the appropriate size.

/edit

OP, I read your blog on this project. You seem to have done a lot of research on this, but also seem to have missed that those coated screws are not approved fasteners for your hangers. And using a 1 1/2" 8 (or maybe it's a 1 1/2" 6) stainless sheet metal screw in a place that you refer to as 'structurally important', is not doing you any good. You essentially spent extra money for an inferior fastener (not as strong and wrong type of thread).

And had you looked on the Grip-Rite page, you would have seen that all of their HDG fasteners meet ASTM A-153 and are approved for use w/ treated lumber. You would have also seen that you could have gotten common nails w/ the Prime-Guard Plus coating, if you didn't want to use HDG fasteners.

One of the things I gather from your blog, is that you think that using a threaded fastening system is better than using the correct nail fastening system. That is just not the case when the threaded fastener is not rated for the application. One thing I will commend you on though, is using the Ledger-Lok fasteners to attach the ledger board to your house. Those things are great, and have made ledger installation a lot easier than the old pre-drill and lag screw method.