# treated lumber on an aluminum boat



## DTHO

looking for some knowledge on this subject, I realize you cant put treated lumber directly onto aluminum. I am in the process of wanting to build two platforms on my boat, these platforms will go over the existing flooring and existing carpet, so there wont be direct contact with the treated lumber and the aluminum. I don't however want there to be any issues, will this be ok? I am concerned with the rain allowing water to reach the lumber and if it drains onto the aluminum frame, rotting or pitting the aluminum. any thoughts? or should I just use pine and start all over again?

thanks for any replies!


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## Bassbme

When you say the platforms you're building are going to go over your existing flooring and existing carpet, do you mean that the plywood will be in contact with the carpet? If so, that's a big no no. You don't want an absorbent material between the plywood you're adding and the flooring that is under your carpet. The carpet will hold water and cause mold and mildew. 

As far as keeping the treated plywood from coming in contact with your aluminum, there are a couple of ways to get around that. First off, even though you're planning on using treated plywood you should coat it with polyurethane to seal out all water. Treated plywood may make the wood less prone to damage from water, but it won't stop water from swelling the wood. I'd put at least two coats of polyurethane on the flat surfaces and 4 coats along any cut edges. The edges will absorb more polyurethane than the flat surfaces of the wood.

The polyurethane will keep the treated wood from coming in contact with the aluminum. But if you bolted it directly to an aluminum member of the boat it could eventually wear through at the contact points. To remedy that you could use thin sheets of plastic or rubber and put it between the plywood and the aluminum. 

Personally, if you're basically just laying new flooring over your old flooring, I'd take the old flooring out and put the new flooring in it's place, with some kind of shield (the rubber or plastic) between it, and the aluminum. It would save weight.


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## DTHO

Thanks Bassbme, that was great info! im thinking I would have better piece of mind just to do it in non treated lumber and coat it with a water sealer rather than using treated lumber. that was a great point you made about the carpet below holding moisture, I will rip that out before installing the platforms. thanks again!


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## MassillonBuckeye

Water sealers need reapplied fairly regularly. I don't think those are recommended for this application.


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## Bad Bub

You don't want to use a water sealer (I.e. Thompson's). You're going to either want to coat it with a resin, epoxy or as bassbme said, a polyurethane varnish. The poly is going to be the cheaper route. But probably the least durable.

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## DTHO

Hey I really appreciate all the feedback! I'm happy I have some place I can turn to, to ask these kind of questions, I got it figured out through all your help! Thanks again!


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## HappySnag

use regular wood and code that with fiberglas reisen,the best choice,
if you use epoxy,you have to use only epoxy paint.
fiberglas will not stick to epoxy.


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## sherman51

you'll be much better off just using exterior grade plywood and coat it with polyurethane to seal the wood. when I did the new floor in my boat I used marine plywood. then someone posted a site on here that said exterior plywood was just as good as marine as far as weather resistance. the exterior plywood just isn't as smooth as marine grade plywood. but it will last just as long if you coat it in polyurethane or some other good sealer.

I didn't know at the time what I should use to coat my plywood with, so I used a paint on truck bed liner. its been about 3 yrs now so only time will tell if I made a good choice. I sealed the edges and cracks with cheese cloth and fiberglass resin on my boat, then added some good carpet from cabelas.

and like bassbme said I would atleast remove the old carpet. and you would be much better off to just replace the old floor. but that's just my opinion.
sherman


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## HappySnag

polyurethane spar,i have bad experience with that,i put 3 coats on plywood and it blister up from sun,and it is expensive.
best fiberglas raisin,people use that on boats in florida and north,it has no problem.if you put marine plywood and you do not treat that ,it will roth like any plywood.

snag


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## hearttxp

Better off using Epoxy Resin-- Ie West systems. Soaks into wood better. 

Fiberglass resin is not water proof ? Gelcoat YES.

Do not use treat lumber either better off with good grade ext or Marine

Research on the internet also


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## dgodek

In an old boat floor I redid, I used untreated true plywood - not OSB - and painted on several coats of resin on all sides. Never had any trouble. Held up for years. If I had more money back then or if it would've been used below the waterline in direct contact with water, I might have used epoxy. Resin is otherwise sufficient.

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## HOUSE

There are quite a few discussions about this online on a website I frequent for modding aluminum boats, and from what I've learned over the years it is okay (and cheapest) to use regular plywood coated with spar urethane. I've used this now on 3 different boat projects without any issue. Two concerns with pressure-treated plywood are that it is heavy, and it contains chemicals that can leech out and cause pitting in aluminum.

Here's one of the debates we had on the boat modding website:
http://www.tinboats.net/forum/viewtopic.php?f=3&t=21365&hilit=plywood


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## bountyhunter

I did one boat I unscrewed the old flr and used it as a templet ,you can sand fit it as you go, use SS screws , alot of good help on here pic out what works for you.


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## erik

i have a 16 foot john boat that has pressure treated wood in it for 20 years every 4 years in put in new carpet and lift the floors out and clean under it-i have had no problems what so ever-so i dont know what the big deal is. this is the first time ive heard of corrosion caused by treated wood.


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## jscheel1

I used spray in Truck Bed Liner on the entire floor of my little fishing boat, prior to replacing floor with 3/4" Marine plywood. The bed liner spray actually made my boat leak free, my pump never runs anymore, and I'm sure the floor will out live me................


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## Nate167

I also agree with bassbme and go with the epoxy. You can even get dispenser pumps that measure it out for you so that the ratios are right. 

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## yakfish

Is there any actual documentation for aluminum boats (or aluminum in general) being damaged by treated lumber? IMO this is a myth. I had an old aluminum boat that I replaced the transom on with a piece of treated 2x8 and I never saw any signs of damage to the aluminum. I also work as a home improvement contractor and have installed replacement gutters over raw treated lumber and have replaced aluminum trim metal over treated wood without any issues. In my experience treated lumber doesn't damage aluminum.


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## I Fish

yakfish said:


> Is there any actual documentation for aluminum boats (or aluminum in general) being damaged by treated lumber? IMO this is a myth. I had an old aluminum boat that I replaced the transom on with a piece of treated 2x8 and I never saw any signs of damage to the aluminum. I also work as a home improvement contractor and have installed replacement gutters over raw treated lumber and have replaced aluminum trim metal over treated wood without any issues. In my experience treated lumber doesn't damage aluminum.


This is old, but, I'll reply. As I understand it, it's not the contact between the two that's the problem. It's the leaching of copper, as in, the treated wood gets wet, copper leaches out, and causes dis-similar corrosion to the aluminum. 

Also, in home improvement type situations, the aluminum trim is usually coated with paint. The interior aluminum of boats generally is not. Even aluminum gas tanks, which are bare, suffer pitting from the chemicals used in foam flotation.


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## afishinfool

My 1958 Alumacraft Flying D has has a marine grade floor, poly coated and carpeted, that has been used for the last 40 years with no problem.


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## tagalong09

I just this summer replaced the floor in my 16 ft Grumman with treated 3/4in plywood decking. it is treated with the new process ,salt water. I want the xtra weight. I covered the walking side with deck over paint from lowes, put fish tank sand on the wet paint, then put on a 2nd coat when that dried.

it worked great this fall in ice, frost, frozen fish slime. 

I am 67 yrs old it don't have to last long!!!!!!!


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## c. j. stone

There is always the option to use Cedar lumber(I'm sure they also use it for plywood?!). All natural and will last longer than you will.....


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## kane10

You will get some corrosion, not enough to cause any significant issues. I replaced my wood floor with aluminum so I never have to worry about rot. My floor will last forever, I also used button snaps on the floor and carpet so cleaning and debris removal is a snap (pardon the pun). When installing the floor I used rivnuts so I can remove the bolts and pull the floor out in about 5 minutes. I also replaced the transom with a couple layers of thick aluminum. My boat has zero wood thus never having to do any repairs. I use my boat year around for fishing and hunting.


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## MassillonBuckeye

yakfish said:


> Is there any actual documentation for aluminum boats (or aluminum in general) being damaged by treated lumber? IMO this is a myth. I had an old aluminum boat that I replaced the transom on with a piece of treated 2x8 and I never saw any signs of damage to the aluminum. I also work as a home improvement contractor and have installed replacement gutters over raw treated lumber and have replaced aluminum trim metal over treated wood without any issues. In my experience treated lumber doesn't damage aluminum.


I think what you are seeing there is water washing the copper away quick or the wood staying dry maybe? In a boat, if it gets wet, and then just sits there, I think that's where you are going to have the issues. If wet and can't drain away.

Definitely not a myth.
http://www.popularmechanics.com/hom...working-with-pressure-treated-lumber-15655848

https://www.oaa.on.ca/professional+...tects+&+practices/pressure+treated+wood+alert

http://www.yellawood.com/resources/pressure-treated-faq.aspx

http://articles.philly.com/2008-11-14/living/25255860_1_pressure-treated-wood-copper-aluminum


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## Lucky Touch Charters

yakfish said:


> Is there any actual documentation for aluminum boats (or aluminum in general) being damaged by treated lumber? IMO this is a myth. I had an old aluminum boat that I replaced the transom on with a piece of treated 2x8 and I never saw any signs of damage to the aluminum. I also work as a home improvement contractor and have installed replacement gutters over raw treated lumber and have replaced aluminum trim metal over treated wood without any issues. In my experience treated lumber doesn't damage aluminum.


The chemical in treated lumber will corrode aluminum overtime. I have seen it numerous times. Infact on a roll of coil stock it clearly states to not install over treated lumber.


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## Lucky Touch Charters

I would recommend using a composite style product. For example TREX decking is a house hold name. It is also made in plywood form. Some boat manufacturers use it. Though it is more than traditional lumber it will outlast and there is no additional work needed such as coatings etc.


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