Pressure treated plywood verses marine grade?

[Okieboatguy]

Ok, this is my first post since I have not seen this really covered in other forums, and I need some insight and knowledge above my current level. I am going to be replacing the floor of a 1984 Bayliner Capri along with the stringers. I know that marine grade plywood uses the waterproof glue and is a much more solid,ie it is more dense, and is made of harder woods and has no gaps unlike the pressure treated. I know pressure treated is made of softer woods so the chemicals can get the into the grains easier and protect it from rot, and it is made using the same waterproof glue as marine grade. The down side of using the pressure treated plywood is the chemicals that will leach out in the water like arsenic and that it is not as solid. The fact that I never want to replace the floor again my instinct is to use the marine grade, but since I have a tendency to over build I am also planning to be fiberglassing the top, bottom and sides of the plywood that is going in to completely seal the floor to prevent the issue from ever happening again. So with that said does it matter the type of plywood I use, and could I even use a non treated hardwood plywood like oak or hickory since it's going to be sealed anyway? Also, I will be putting floor drains in, something Bayliner forgot to put in, to help properly channel out the water. As well as any wood that goes in I plan to place at least a single layer of fiberglass on, and if it is exposed it will get additional layers and gel-coat. My goal is to have removable carpet, and be able to pressure wash the inside if needed like my last Carolina Sludge I used to own. So what are everyones thoughts, and where am I going wrong in my thought process? Am I over thinking what needs to be done?

 

[Bondo]

Re: Pressure treated plywood verses marine grade?

Ok, this is my first post since I have not seen this really covered in other forums, and I need some insight and knowledge above my current level. I am going to be replacing the floor of a 1984 Bayliner Capri along with the stringers. I know that marine grade plywood uses the waterproof glue and is a much more solid,ie it is more dense, and is made of harder woods and has no gaps unlike the pressure treated. I know pressure treated is made of softer woods so the chemicals can get the into the grains easier and protect it from rot, and it is made using the same waterproof glue as marine grade. The down side of using the pressure treated plywood is the chemicals that will leach out in the water like arsenic and that it is not as solid. The fact that I never want to replace the floor again my instinct is to use the marine grade, but since I have a tendency to over build I am also planning to be fiberglassing the top, bottom and sides of the plywood that is going in to completely seal the floor to prevent the issue from ever happening again. So with that said does it matter the type of plywood I use, and could I even use a non treated hardwood plywood like oak or hickory since it's going to be sealed anyway? Also, I will be putting floor drains in, something Bayliner forgot to put in, to help properly channel out the water. As well as any wood that goes in I plan to place at least a single layer of fiberglass on, and if it is exposed it will get additional layers and gel-coat. My goal is to have removable carpet, and be able to pressure wash the inside if needed like my last Carolina Sludge I used to own. So what are everyones thoughts, and where am I going wrong in my thought process? Am I over thinking what needs to be done?

Ayuh,..... Welcome Aboard,.... In All Honesty,... yer over-thinkin' it....

A 1984 Bayliner made it this far with less than the best plywood,.... that's 28 Years...

Use exterior grade plywood, 'n glass it...
Keep it Drained, ventilated, 'n dry,...
It'll last Another 28 years....

 

[glenn property of pam]

Re: Pressure treated plywood verses marine grade?

Arauco Plywood from lowes seems to be a iboat favorite as its ext grade sanded on one side and about half the price of marine i think i payed $38 for 1/2 and $43 for 3/4. preasure treated should not be used as the bond to fiberglass will fail over time due to the cemicals. hope this helps

 

[Bob_VT]

Re: Pressure treated plywood verses marine grade?

An older bayliner will survive longer then you will own the boat with exterior grade. I agree arauco is great but still not worth the extra money.

A restoration will take a deep enough bite from the wallet no need to feed it more. You have a boat year and manufacturer that is renowned for poor materials and construction. If it was a higher end boat I would encourage the good stuff but not bayliner.

FYI pressure treated no longer contains arsenic however it contains copper and chemicals that attack fasteners. It must be well dried inside befor resins will adhere properly and last and is actually heavier. Not worth it for use.

 

[Isaacm1986]

Re: Pressure treated plywood verses marine grade?

Well in my opinion for whatever it is worth. Why not just use the pressure treated wood without fiberglassing it in? Save the cost of the fiberglass. afterall I think the point of pressure treated wood is to prevent it from rotting.

If you go with the exterior grade plywood, then I would definitively fiberglass it in to protect it from the elements.

I personally have worked on a lot of fiberglass boats, and I have put pressure treated wood in almost all of them. I restored and sold a bayliner to a friend of mine 5 years ago. It has a pressure treated deck with no fiberglass and it has held up just fine. I was on the boat this last weekend, and the deck is as solid as it was when i put it in.

I will clarify that I did tab the deck to the boat with fiberglass. I used fiberglass and epoxy and glassed around the edges of the deck to the boat. I just did not glass the whole floor in.

I know that this is not a very popular opinion here on the forum, but I think it works just fine.

 

[Gpayne]

Re: Pressure treated plywood verses marine grade?

Just my $.02, I just redid the floor in a 1990 Sunbird 17' I picked up cheap a couple weekends ago. The original floor was glassed over the top, but not the bottom. It started rotting from the ski locker out. Luckily I caught it in time before it got to the stringers. I cut out the rotten section, roughly 5'x6', and replaced it with 15/32" (1/2") exterior grade, and I painted the new pieces with two heavy coats of UGL Drylok masonry sealer. I didn't re-glass it, but when I put it back in the boat, I sealed every joint, seam, and screw hole with 3M 5200 sealant. I've used Drylok for various projects over the years, and always had great results. It's alot cheaper than fiberglass, and alot easter to use. Having said that though, if I was doing a complete resto, yes I would most likely glass everything the way it's supposed to be. However, when replacing a section of rotten floor in a boat I don't plan on keeping more than a couple years anyway, I figure Drylok will be just fine.

 

[Jlawsen]

Re: Pressure treated plywood verses marine grade?

Bondo and Bob, you got it right. But hey, you should by now...

The myth that Marine Ply uses water proof glue is just that however it does have fewer voids and the idea behind that is that it will survive the stress of the marine environment better and it does. SuperPly from Roseburg lumber is the stuff that uses waterproof glue. That's just for your info and not a recommendation. I always just go with ACX fir plywood from Home Depot. 5/8 is plenty thick but if you're going to glass it, drop back to 1/2" and that will keep you from having to adjust things due to the added deck height. Other than being a pain in rear to change out, they aren't a real big deal and the less expensive wood will last longer than you'll keep that boat.

 

[Bob_VT]

Re: Pressure treated plywood verses marine grade?

Well in my opinion for whatever it is worth. Why not just use the pressure treated wood without fiberglassing it in? Save the cost of the fiberglass. afterall I think the point of pressure treated wood is to prevent it from rotting.

If you go with the exterior grade plywood, then I would definitively fiberglass it in to protect it from the elements.

I personally have worked on a lot of fiberglass boats, and I have put pressure treated wood in almost all of them. I restored and sold a bayliner to a friend of mine 5 years ago. It has a pressure treated deck with no fiberglass and it has held up just fine. I was on the boat this last weekend, and the deck is as solid as it was when i put it in.

I will clarify that I did tab the deck to the boat with fiberglass. I used fiberglass and epoxy and glassed around the edges of the deck to the boat. I just did not glass the whole floor in.

I know that this is not a very popular opinion here on the forum, but I think it works just fine.

Agree. Since it is a cheaper boat I agree and it would work. I think it will get slimy and be ugly as sin. Remember it does attack the wrong screws.

 

[Jlawsen]

Re: Pressure treated plywood verses marine grade?

If you go with the exterior grade plywood, then I would definitively fiberglass it in to protect it from the elements.

5/8 ACX and two coats of 1 part polyurethane with extra attention at the edges will last a long long time. That's what the manufacturers do (the better ones anyway).

 

[Isaacm1986]

Re: Pressure treated plywood verses marine grade?

Agree. Since it is a cheaper boat I agree and it would work. I think it will get slimy and be ugly as sin. Remember it does attack the wrong screws.

Yes. We just laid some outdoor carpet over it and it works great so far.

 

[jigngrub]

Re: Pressure treated plywood verses marine grade?

Pressure treated is less than desireable, it will have large voids between the plies. It will also be wet from the pressure treating solution, this will be bad for any kind of sealing or painting unless you let it dry out completely for a couple months in the hot summer sun.

Marine grade is good stuff, but is very expensive and it will become water damaged and rot if not sealed.

The Aruco is good stuff, ABX with small voids.

An even better product than Aruco is MDO plywood, it's mainly used for building exterior signs and used in concrete form construction. You can read about it here:
http://www.google.com/search?source..._enUS440US440&q=mdo+plywood+for+boat+building
It is half the price of marine plywood and a better product IMO.

 

[ondarvr]

Re: Pressure treated plywood verses marine grade?

5/8 ACX and two coats of 1 part polyurethane with extra attention at the edges will last a long long time. That's what the manufacturers do (the better ones anyway).

I know of no builder that uses this method.

 

[mrdjflores]

Re: Pressure treated plywood verses marine grade?

just a thought about marine grade....and i may have been mislead....but i was informed a few years ago that 'marine' plywood layers are not bonded to each other with waterproof glue...but instead, each layer is bonded using epoxy instead of glue.

thoughts?

 

[ondarvr]

Re: Pressure treated plywood verses marine grade?

This subject has been discussed so many times on this site you can find a thread on the subject on just about any page. Scroll down a short distance on this page and will find a list of related questions.

Marine ply is great, Marine PT for is better for what you want to do.

If you do a good job any of the types of plywood will work well and last longer than you will own the boat. Do a poor job and they will all fail, some just sooner than others.

Add up the cost of using the various different products and methods and then see which ones fit into your budget. After that use a great deal of attention to detail and it will last for decades.

 

[ondarvr]

Re: Pressure treated plywood verses marine grade?

just a thought about marine grade....and i may have been mislead....but i was informed a few years ago that 'marine' plywood layers are not bonded to each other with waterproof glue...but instead, each layer is bonded using epoxy instead of glue.

thoughts?

just glue

 

[jigngrub]

Re: Pressure treated plywood verses marine grade?

This subject has been discussed so many times on this site you can find a thread on the subject on just about any page. Scroll down a short distance on this page and will find a list of related questions.

Marine ply is great, Marine PT for is better for what you want to do.

If you do a good job any of the types of plywood will work well and last longer than you will own the boat. Do a poor job and they will all fail, some just sooner than others.

Add up the cost of using the various different products and methods and then see which ones fit into your budget. After that use a great deal of attention to detail and it will last for decades.

just glue

WBP glue.

Wiki and a couple other places say this about that.

Marine plywood

Marine plywood is manufactured from durable face and core veneers, with few defects so it performs longer in humid and wet conditions and resists delaminating and fungal attack. Its construction is such that it can be used in environments where it is exposed to moisture for long periods. Each wood veneer will be from durable tropical hardwoods, have negligible core gap, limiting the chance of trapping water in the plywood and hence providing a solid and stable glue bond. It uses an exterior Water and Boil Proof (WBP) glue similar to most exterior plywoods

 

[mrdjflores]

Re: Pressure treated plywood verses marine grade?

WBP glue is what i thought it was....

Water and Boil Proof glue.....hmm...if my boat is boiling...i think i may have bigger things to be worried about....LOL

 

[Yacht Dr.]

Re: Pressure treated plywood verses marine grade?

Not this again ..

Another thread about plywood .. within 24 hours there is like 20 post ( one post from the OP and 19 from members without the OP involved in the discussion at all ) ...

I would suggest searching the Iboats Resto forum and you can find all kinds of Pros and Cons, Ins and Outs, Application to application, Temperment of the ply, Warp, Saturation of resin VS. thing, Cost, Dry time ETC.

YD.

PS. *cough* Marine Grade Doug for stringers and Transoms *cough*