Why not pressure treated plywood?

[daveydoodle]

Re: Why not pressure treated plywood?

I posed a similar question a few mo. ago, started re doing my alu. Alumicraft floor and decks. It was suggested and very cost effective to use plain exterior grade ply. with several coats of "Defy" a epoxy fortified stain (saversystems.com) paying particular att. to the edges. The prev. owner tried replacing the wood with PT on the foreward raised seating and livewell area and it was all twisted ,warped and bubbled up even tho screwed down substantially. I am gluing vinyl over the decks and the tech. dept assured me of no lack of adhesion. For the only reason of you dont know what PT it going to do when dried I would not put in a boat.

 

[sprintst]

Re: Why not pressure treated plywood?

Or you can find some dude who keys it in at the same price as regular plywood My bad for not saying anything at the time...must have slipped my mind. I was probably preoccupied with thinking about how much more money this big chain store was making than me.

 

[ondarvr]

Re: Why not pressure treated plywood?

...

 

[ondarvr]

Re: Why not pressure treated plywood?

I've never seen so much info on one posting.

After 20 years use, I replaced the back end sheet of plywood on my pontoon boat 5-6 years ago with regular painted plywood. Water blowing in our boathouse door promptly rotted the replacement plywood. The front 5 sheets of OEM marine plywood is as solid as it was when the boat was new.

Marine plywood must be purchased at a specialized wood or plywood supplier, and is available in virtually any major city. It's expensive to order online due to high delivery costs. Sometimes you've got to call around to find it. Lowes/Home Depot doesn't sell such specialized products.

There are many types of marine ply made from many different types of wood, some are very rot resistant because of the natural resins in the wood, and others have very little rot resistance. Fir marine ply has good rot resistance, exterior grade fir can be OK depending on quality.

The plywood you have that didn?t rot may be the PT marine product discussed above. Fir extirior ply can be tough to find in the south, so it frequently needs to be special ordered in that part of the country.

 

[master bowman]

Re: Why not pressure treated plywood?

What about CDX plywood?

 

[ondarvr]

Re: Why not pressure treated plywood?

What about CDX plywood?

In the west CDX is normally fir and is an exterior product.

 

[oops!]

Re: Why not pressure treated plywood?

, I just can't afford/stand to do the same job twice!

then use an exterior grade plywood (waterproof glue between the laminates)......and properly do the job.....it will last 20 or thirty years with nominal care.

or you can keep questioning after tons of info has been thrown your way.....lay down pt ply.....and have the whole alum frame of the ship crumble underneath you..

your call

 

[chriscraft254]

Re: Why not pressure treated plywood?

Halfmoa, there are differnet ways to get around the corrosion issues. Coming from a home builder of almost 25 years I can attest to the dissimilar metal issue with treated plywood and metal structures. Because that is what you are dealing with is disimilar metals. The treated wood has copper infused into it along with other preservatives. I understand your concern because treated ply is much much cheaper than marine ply or the twelve other synthenthetic materials there using to build boats these days.

That being said, I have rebuilt many houseboats over the years and a couple run abouts. If you want to use the treated plywood, go for it! Just make sure you put a barrier coat on the aluminum and the fasteners if used. Its also not a bad idea to put a plastic between your ply and boat structure. This you will see all the time on home building but vary rarely see it in the boat building industry. Also if you resin the ply or coat it with a barrier coat, you will trap the aluminum inside the barrier caot. remember though, it is a good idea if using fasteners to coat them as well.

Though your application is much different, I have re-built full transoms many times out of pressure treated wood and glassed over and gel coated. The transom will out live the boat. No problems to date with delaminating or corrosion caused by the treated lumber. But again, I take extra steps to not have metal touch directly to it.

One thing to consider, and it has been already mentioned, is use a dry kiln pressure treated, the voids will be already filled and it is a better product than you will find at your local lowes/home depot. Its also more expense. But still not as expensive as the marine ply.

Good luck with your project.

 

[master bowman]

Re: Why not pressure treated plywood?

In the west CDX is normally fir and is an exterior product.

Sorry for the lack of misunderstanding. But Is this a do or dont? i am planning on building a removable false floor in my boat, and this feed is very helpful. Seems like the one guy is just disagreeing to get a rise out of people. With so much info offered to him i do not understand how he thinks he is going to get "Burned," at this point i think the only way he is gonna get burned is if he doesnt listen.

Thank everyone here on iboats. There is such a vast amount of knowledge that everyone is offering here. I'm really glad i found this forum.

I have a great feeling that i wont get steered in the wrong direction with any of my boating questions.

Many thanks.

 

[starcrafter65]

Re: Why not pressure treated plywood?

I don't understand theses threads about plywood....they make an actual product for boats called marine plywood - you can actually build a hull from it! After 2 boats - it costs an additional - what - hundred bucks to use marine ply? Why anyone would want to take a residential homebuilding product - and coat it with fiberglass that is going to have holes poked in it anyway - and negate the cost savings - to make it "equal" ......


As my father in law said - "Well - it is a boat....."

 

[jasoutside]

Re: Why not pressure treated plywood?

Why anyone would want to take a residential homebuilding product

Why? Simple, costs less.

Arauco Ply will do the exact same job as MG at a 50% (minimum) savings. (At least in the applications that I have used it)

I used MG on my Islander transom. I'll be worm food before it needs to be replaced.

I used Arauco on my Jet transom. I'll be worm food before it needs to be replaced.

Difference? Cost, as I am covered with dirt either way in the end.

 

[jigngrub]

Re: Why not pressure treated plywood?

On this forum:

Everything has to be wrapped in glass and some kind of resin as long as it doesn't have wax in it.

Everyone is terrified of PT lumber no matter what type.

It's perfectly ok to use home building products in your boat, but NEVER start a tread and say or ask if you can use anything automotive on your boat!!!

 

[halfmoa]

Re: Why not pressure treated plywood?

or you can keep questioning after tons of info has been thrown your way.....lay down pt ply.....and have the whole alum frame of the ship crumble underneath you..

your call

All I was after was an answer based on fact instead of opinion, of which I recieved and am appreciative! And as previously stated, I've been burnt by literally 100s of incorrect answers on another forum assuring my that the product I wanted for a specific application was correct when in fact it was absolutely incorrect.

Thanks again everyone!

 

[halfmoa]

Re: Why not pressure treated plywood?

On this forum:

Everything has to be wrapped in glass and some kind of resin as long as it doesn't have wax in it.

Everyone is terrified of PT lumber no matter what type.

It's perfectly ok to use home building products in your boat, but NEVER start a tread and say or ask if you can use anything automotive on your boat!!!

Ain't it the truth!!!!!

 

[Cadwelder]

Re: Why not pressure treated plywood?

I truly understand your frustration with the term ?experts? as I too have the same feelings on many subjects because experts also disagree on their given fields of expertise. The bottom line is there is no single answer for any question when it comes to building a boat, a car, a plane, or really anything else for that matter.

The term expert: 1. A person with a high degree of skill in or knowledge of a certain subject.

Notice it doesn?t say someone that knows everything about a certain subject, and that?s because no one really does. Only time tells the answers to any material and then there are many factors that go into that, did the guy that installed it, do it right, did they mix the material right, etc. etc. I?ve learned after many years of life that nothing is exact and no one has all the answers about anything. It all boils down to what you are comfortable with.

Then there are the professionals: a : of, relating to, or characteristic of a profession b : engaged in one of the learned professions c (1) : characterized by or conforming to the technical or ethical standards of a profession (2) : exhibiting a courteous, conscientious, and generally businesslike manner in the workplace

A professional anyone is just a person that does a given trade for a living, it doesn?t make them an expert, but I still tend to listen to them because the more experience anyone has the better their opinions should be. Again?time will tell

This is why polyester resin is recommended here all the time?time tested and proven. Marine grade plywood is recommend?time tested and proven. This does not mean you can?t use CDX plywood and epoxy it just means many know the other products work fine. I?ve used pressure treated plywood many times and personally have never been satisfied with the results, so I don?t use pressure treated for anything or recommend it.

Most any subject boils down to ?this has what has worked well for me? and iboats has some of the best opinions I?ve read anywhere on the web. Now to say the information here is never wrong, well I don?t think anyone here will say that?as we all make mistakes. However, I think you?ll get the best answers for any boating question here and usually with a ?reason? to back up the recommendation. I?m sorry for the bad experience you had on a previous forum, but don?t let that experience ruin this one for you. Do some reading on your own, research on your own, listen to others, read some more and then decide what is best for you?.

Sorry for being longwinded

CW

 

[Woodonglass]

Re: Why not pressure treated plywood?

The above ^^^ should be a sticky at the top of the forum. Very nicely done, CW!!!!

 

[halfmoa]

Re: Why not pressure treated plywood?

Thanks CadWelder. Well stated thoughts. And thanks to everyone else who chimed in! I think this has been one of the best threads I've read in quite a while!

 

[ezmobee]

Re: Why not pressure treated plywood?

I don't understand theses threads about plywood....they make an actual product for boats called marine plywood - you can actually build a hull from it! After 2 boats - it costs an additional - what - hundred bucks to use marine ply? Why anyone would want to take a residential homebuilding product - and coat it with fiberglass that is going to have holes poked in it anyway - and negate the cost savings - to make it "equal" ......

Marine ply is not treated against rot. It is a superior product with varying better qualities (usually fewer to no voids, cross grain plys, more plys, better glues...things like that) but is not treated. It will still rot if not sealed. For many of us, that "lasting a little longer" quality just isn't worth the cost especially when the required sealing effort is the same. I will admit, the regular exterior ply I got from Home Depot for my deck was total crap. Void city! However, the Arauco I got for my transom was super nice. I didn't see a single void when I cut it out. Still half the cost of marine.

 

[Woodonglass]

Re: Why not pressure treated plywood?

And with MDO/HDO you get the best of both worlds, IMHO!!!!

 

[starcrafter65]

Re: Why not pressure treated plywood?

Why? Simple, costs less.

Arauco Ply will do the exact same job as MG at a 50% (minimum) savings. (At least in the applications that I have used it)

I used MG on my Islander transom. I'll be worm food before it needs to be replaced.


I used Arauco on my Jet transom. I'll be worm food before it needs to be replaced.

Difference? Cost, as I am covered with dirt either way in the end.

Well The Arauco may be void free - but MG is formed with fully waterproof structural adhesive made for wet conditions - I needed 4 sheets for my Holiday - the difference is 80 bucks........and for all the $ I spent

All that being said - it is all about how long things last - and if the lifespan works - then you are correct - I think everyone can say everything regarding what works - but the number one factor in longevity is the sustained atmosphere the wood is subjected to - if you have wet carpet and a bilge with wet foam and consistant water under the floor - and keep your boat in a slip - that is no comparison to dry conditions above and below the floor