I have dock located on a brackish (salt/fresh water mix) body of water. It is built with appropriate (for the area) pressure treated lumber, though I am not sure of the exact type of preservative.

I want to build a lower level platform to make it easier to access canoes, kayaks, and smaller watercraft, similar to what is shown here:

enter image description here

What kind of fasteners and hangers should I use? I have been looking at various types of Hot Dipped Galvanized (HDG), Zmax, and stainless. Stainless is my first choice, but a couple of questions arisen. The stainless hangers are not as heavy duty (18 gauge), in so far as their load carrying capability is, as some of the HDG or Zmax (16 or 14 gauge) products. But the stainless parts would work with approximately 4X margin, while the heavier parts would have 6X or 8X margin.

Also, with the stainless parts, I am limited to using stainless 3-1/2" nails, as structural screw-type fasteners do not seem to be available in stainless. I cannot use any sort of galvanized fastener with stainless. With the HDG or Zmax hangers, I can use the appropriately finished structural screw type fasteners.

Any thoughts on whether I should go with stainless or the HDG/Zmax products?

EDIT 1 - Existing dock hardware

FYI, the dock is built with all galvanized hardware - large nails (no bolts or screws); nothing stainless. The boat lift (not shown in this picture) uses stainless hardware for the pulley and cable system.

The dock went through the proper permitting process when it was built, which included a professional survey, local jurisdiction approval, Dept. of Natural Resources approval, and (I think) Army Corp of Engineers approval (standard for anything on the waterfront around here).

Edit 2 - Decision

I decided to go with the thinner stainless steel (316) hangars, with SS nails, instead of one of the thicker, galvanized versions.

  • Unfortunately, this is partly a matter of opinion and partly a shopping/product recommendation question. Can you rephrase to ask something more objective and specific? – isherwood Jul 9 at 13:50
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    Make sure your port authority doesn’t have specific regulations, I did some work a few years back and the port authority was a bigger pain in the butt than any electrical inspection I have ever had, they specified the materials allowed right down to the fasteners. Being in the tidal zone every thing was looked at with a microscope, so I would check you may not have the issue at your location. – Ed Beal Jul 9 at 14:01

The stainless is thinner because it is not going to rust away like galvanized steel. The choice depends on the service life needed ; local experience experience should indicate life for galvanized -5yr, 10yr, ?. I would use stainless deck screws in the stainless. The stainless will show rust pits but more appearance problem than structural.

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  • Deck screws, stainless or not, are not approved for use in joist hangars and the such, per the manufacturer's guidelines. – SteveSh Jul 9 at 17:57
  • You mean I need to replace the deck screws that have been in my deck joist hangers for 25 years? – blacksmith37 Jul 10 at 16:48
  • That's up to you. I was just stating why I won't be using deck screws for this, or any other structural application. – SteveSh Jul 10 at 17:43

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