stainless steel screws on pressure treated plywood

[dancudayo]

Sorry guys, did a search but couldn't find it, I can't remember what everyone was saying about this. Can you use stainless steel screws on pressure treated plywood? I need to use it on stringers to make longer length and also to screw floor down to stringers, if not what was recommended, bronze/copper? Thanks again, Dan

 

[jameskb2]

Re: stainless steel screws on pressure treated plywood

Hello Dan,

It depends on the method of pressure treating. CCA treated will not corrode (significantly) most fasteners including steel or aluminum. ACQ (the "new" stuff) will corrode aluminum rapidly, mild steel slowly.

Fasteners for use with ACQ are hot dipped galvanized (not electro galvanized) and stainless. I'm not sure about copper or brass.

Stainless fasteners are graded too. There are different types of stainless. Some are "pure" and very hard, some are mild and softer, more prone to corrosion. It has to do with the alloy's mix.

 

[marine4003]

Re: stainless steel screws on pressure treated plywood

To answer your question...Yes.and even the lesser grades of stainless will work.

 

[Robj]

Re: stainless steel screws on pressure treated plywood

I would only use stainless screws. For fastening my deck to stringers I used stainless deck screws, they weren't that expensive. My wood was pressure treated CCA. I would try and stay away from the ACQ if I could.

Have a great day,

Rob.

 

[OV1961]

Re: stainless steel screws on pressure treated plywood

When we rebuilt our front porch we used pressure treated lumber and 316 stainless screws. Because we live close to the Chesapeake Bay it is highly recommended not to use plain steel fasteners, even coated ones, because the salt will corrode them in just a few years. If your boat is near salt water, even if you don't boat in salt water, you should use stainless.

When I took up the original 1961 floor in my boat (search for the thread here) the stainless screws they used were still good as new, except for the philips slots were plugged with resin. The wood around the screws was rotted and some later do-fer deck screws were pins of rust.

 

[BillP]

Re: stainless steel screws on pressure treated plywood

Yep, SS for ACQ but like suggested already try to find CCA treated ply. Then you can use galvanized, bronze or SS. I've pulled electo and hot galv screws sealed tight in glass on standard ply from boats 35 yrs old and they looked new. Some were shiny and others dull but not rusted or wasted. If you glass and seal the fasteners well the main concern is chemical reaction from the pt process and CCA is the least hostile pt to them.

For trivia...Very little (as close to zero as it gets on production boats or custom) SS was used in 1961 for boatbuilding. It was really rare and extremely expensive to buy SS fasteners back then...but monel was used like SS is today and probably what ov1961 found.

bp

 

[marine4003]

Re: stainless steel screws on pressure treated plywood

See the problem here is there is no CCA lumber out there,its all ACQ, CCA was banned due to its arsenic composition,seems lawsuits against the manufacturer of the preservative got rid of a good thing.

 

[reelfishin]

Re: stainless steel screws on pressure treated plywood

See the problem here is there is no CCA lumber out there,its all ACQ, CCA was banned due to its arsenic composition,seems lawsuits against the manufacturer of the preservative got rid of a good thing.

I was in 84 Lumber last month and they had a choice in PT lumber, at least in long boards. I didn't check on plywood. They had more CCA than ACQ in stock.
I was told that if I wanted the ACQ I'd have to special order it and that is cost a bit more. All the lumber on the racks still had the little blue CCA labels stapled on the ends. The overall quality of their selection was poor though, it took me an hour to find 4 good 2x12s. They did have a warning about using CCA on playground equipment though.

 

[dancudayo]

Re: stainless steel screws on pressure treated plywood

good news, and the wood I got is the old stuff, I've had it for 4or 5 months so it is nice and dry. Monday I'm going to finish glassing in the transom and then move on to bedding the stringers. Messed around with resin and fiberglass off and on for a few months, I think I might have the hang of it now. I enjoy doing this kind of stuff and reading all the articles to get ideas on how to do it, thanks all for the input, Dan

 

[BillP]

Re: stainless steel screws on pressure treated plywood

See the problem here is there is no CCA lumber out there,its all ACQ, CCA was banned due to its arsenic composition,seems lawsuits against the manufacturer of the preservative got rid of a good thing.

In 2003 the EPA banned CCA for use only in residential construction, playgrounds, etc because it "can" cause cancer. They had nothing that said it "has" caused cancer or that homes built with it are dangerous to live in. CCA is still legal for commercial use in the USA and doesn't require a license to buy it. It's easy to find in Florida.

bp

 

[marine4003]

Re: stainless steel screws on pressure treated plywood

Interesting....Locally you cant find it,i can still get Marine Grade lumber,but true CCA is no longer available...and i was told we cant get it?????????

 

[BillP]

Re: stainless steel screws on pressure treated plywood

Maybe it's restricted at local or state level where you live. It's here at Lowe's and HomeDepot by the truck loads.

 

[OV1961]

Re: stainless steel screws on pressure treated plywood

For trivia...Very little (as close to zero as it gets on production boats or custom) SS was used in 1961 for boatbuilding. It was really rare and extremely expensive to buy SS fasteners back then...but monel was used like SS is today and probably what ov1961 found.

bp

I stand corrected. I remember monel fasteners from Navy valve repair days. Non ferrous and non-corroding. As I recall our nickels (the Jefferson and Buffalo type) are close to being monel. You can use them for making washers in a pinch I did not know SS was uncommon back then.

 

[BillP]

Re: stainless steel screws on pressure treated plywood

I stand corrected. I remember monel fasteners from Navy valve repair days. Non ferrous and non-corroding. As I recall our nickels (the Jefferson and Buffalo type) are close to being monel. You can use them for making washers in a pinch I did not know SS was uncommon back then.

It's the nickle that makes monel so good and also makes it way less prone to crevice corrosion. It was the "other" corrosion resistant fastener used in the 60s. Of the good stuff, bronze and monel were most common. Some ply kit boats like Sears kits actually used galv or brass. SS was available but really expensive and rarely seen. It suffered crevis corrosion and arrived on the marine scene in the late 1970s. All the fasteners and boat hardware you see common today in SS was in bronze and chromed bronze back then. Higher end was the monel. Times have changed and now bronze is expensive and SS the common and cheaper variety. Here's some 60s trivia...OMC sold titanium bolts for mounting their ob motors.

bp