Floor plywood question - need input please

[jjustice]

OK, I need some guidance with this issue. I have a ’78 Argosy 27’ that had the old gold (from the 70s rug) that I have taken out. I plan to replace it with linoleum flooring that looks like wood. This type of linoleum “floats”. It is in strips and glued together on the edges. The plywood floor under the rug is in OK condition, no rot but many stains. I want to seal the plywood floor to preserve the wood and make a solid surface for the new linoleum. What would be your suggestions here? Thanks

[utee94]

West System epoxy is probably the most durable. It won't be cheap to do that much area, though. You could go with something like Thompson's or Olympic water seal in the main field area, and then hit the edges with epoxy, since the edges get the most water from exterior leaks, and interior leaks that shift toward the edges for egress.

If you're just interested in making a smooth, level base for the new floor, then I'd put down a skim coat of Ardex (you can find this at local flooring supply houses, but probably not the blue or orange boxes). You could do the Ardex over the water seal and/or epoxy too, if you like.

Just curious, which plank-style product do you plan to use for the new flooring?

Good luck!
-Marcus

[overlander63]

Thompson's Water Seal would probably be a good choice. It is supposed to last many years outdoors in the weather, so should last indefinitely indoors, under a carpet. Just read thje directions to make sure it can be used in that manner.

[jjustice]

thanks for the info. What about a polyurethane for a sealer?

[utee94]

Sure, you could use poly as a sealer. Would probably work a bit better than the water seals. Although I wonder if you could use both? The water seals are designed to penetrate, and poly is made more to seal the outside surface of the wood. The two together would probably be fairly formidable, unless they might react badly in some way to one another.

[Cantrell]

The Thompsons has a high linseed oil content. Polyurethane over the top of that would not adhere properly so go with one or the other. The Thompsons might give you a little offgasing stink over time--don't know--never used it inside an enclosed space. Once the poly cures, though, the stink is done.

[utee94]

Originally Posted by Cantrell

The Thompsons has a high linseed oil content. Polyurethane over the top of that would not adhere properly so go with one or the other. The Thompsons might give you a little offgasing stink over time--don't know--never used it inside an enclosed space. Once the poly cures, though, the stink is done.

Thanks, I suspected something like that might be the case.

For what it's worth, I sealed the the top of my new floors with poly, the bottoms with Thompson's water seal, and used a penetrating wood hardener/rot inhibitor on the open plywood edges. HOWEVER, if I had it to do again, I'd use epoxy around all of the open plywood edges, it's the best.

[byamcaravanner]

Sealing the plywood below a floating floor can be a double edged sword... It will retard absorption of moisture into the sub-floor and can help to minimize decades of accumulated orders in the floor, but at the same time this will serve to trap moisture between the sub-floor and the finish floor. This is not a good thing.

...So, there are benefits, but also detractors

[utee94]

Originally Posted by byamcaravanner

Sealing the plywood below a floating floor can be a double edged sword... It will retard absorption of moisture into the sub-floor and can help to minimize decades of accumulated orders in the floor, but at the same time this will serve to trap moisture between the sub-floor and the finish floor. This is not a good thing.

...So, there are benefits, but also detractors

Good point, Steve. My flooring is not floating, it is permanently affixed VCT with strong VCT adhesive.

[VIKING]

You could also use a water-based polyurethane floor finish. No off-gassing, and easy to apply. I used this to seal under my flooring before I installed it.

Rich the Viking

[87MH]

Originally Posted by jjustice

thanks for the info. What about a polyurethane for a sealer?

In my opinion, Thompson's is crap...

I used it many years ago and was REALLY disappointed with the product. At the very least, comparison read the ingredients on the can prior to purchase. Epinions.com only gave it 2.5 stars with 13 reviews - it would be a lot less if I had posted. Several of my friends have had similar experiences to mine.

I primed my floors on the redo of both the '87 MoHo and the '78 Sovereign with a good paint primer - Oil base primer would be better than Water base if you have time to let it dry...Polyurethane would be OK, but again, IMO, oil base is better than water base.

Anything that will penetrate and last would do a good job...Thompson's has no suspended solids for the sealing agent to bond to.

Since no one will see the color an option would be to purchase an "oops" paint from one of the big box stores (an off color mix or some other cause to be rejected by a consumer). These paints are sold at a very deep discount (like, 75%), and are really a good quality paint. Just go with a high end exterior paint since that is one job you certainly do not want to do twice.

[ts8501]

I like what Bob Thompson wrote in this link here.

"it is not all that necessary to coat the wood with fiberglass resin or epoxy.... seal it with 3 coats of boiled linseed oil. The "lin" in linseed oil is a basic ingredient in "linoleum" and most oil based paints. Mix the boiled linseed oil, 1 part boiled linseed oil to 3 parts mineral spirits, then apply 3 coats to the wood or until the wood will no longer absorb it. The mineral spirits will allow the linseed oil to penetrate deeply into the wood. This will seal the wood against absorbing the moisture which would lead to decay and rot. Be sure to not use a copper based wood preservative as it may react with the aluminum. Boiled linseed oil and mineral spirits should be readily available at Wal-Mart or any building supply store. -Bob Thompson"

[Jim & Susan]

I like Dennis' idea with the oil based paints. Makes a lot of sense.

But, I did something similar to UTEE. I used the West epoxy around the perimeter/edge of the floor, then used verathane in the main field areas (top and bottom for both). I also used the epoxy underneath the entire piece in the bath. We have a rear bath. The bath takes up one sheet of ply back there in ours, so we had just enough left over from the perimeter/edge application for the bath area. It only took one quart of the West epoxy and one gallon (IIRC) of the verathane.

Let us know what you decide and post a few pics. A new floor really makes you feel good about your progress.

Jim

[tallytwo1994]

Originally Posted by utee94

If you're just interested in making a smooth, level base for the new floor, then I'd put down a skim coat of Ardex (you can find this at local flooring supply houses, but probably not the blue or orange boxes).

If you decide to use a leveling product be sure to chose one that is flexable enough for the movement of a TT. These are cement based, and most will crack under movement. Call the munufacturer and ask about this specific application.

Carol

[hampstead38]

Good thread. I haven't had much luck with Thompson's in other applications. I haven't tried West Expoxy but it looks interesting. As for leveler, I would worry about a concrete type leveler, even just a skim coat. My idea is to fill the major defects with a wood compound and then put down a good layer of thin, high quality ply run "crossways" to the floor. Maybe I'm bass ackwards, but I figure it can't hurt to do a layer over the existing floor, covering the seams.

So, with a good adhesive holding down a very smooth layer of plywood, I figure the subfloor is ready to go except for sealing it. Epoxy might be overkill. I figure any high quality sealer is going to do better than the original untreated plywood... and honestly, 90 percent of my floor in the Overlander was still solid when I pulled up the old carpet.

[barts]

On our Airstream we used a low viscosity epoxy, thinned w/ Xylene for one or two coats, filled any holes w/ epoxy + microballons and finishing w/ a coat of plain epoxy. I wet sanded w/ 200 grit in between coats, and finished it w/ a coat of aluminum filled moisture curing polyurethane paint.

[Aerowood]

I used as the final coats, cement floor epoxy. It was really thin and really penetrated. I put on three coats sanding between coats.

Kip

[SilverHoot]

I copied this text from some boat building web site (I'm trying to find it now). I have not tried this but sounded interesting. Here's the text:

[I]Start with a small amount of resin (depending on project size) and thin it down with 4 to 6 parts acetone until it's almost like thick water. This is the secret, because the acetone will soak deep into every one of the most microscopic pores and fibers of the wood or other material. It really soaks in, carrying the resin with it. It's application is so light and thin, that it tolerates wood flexing without problem. It becomes an integral part of the wood or concrete and it will not crack or separate.
*
You'll need to use far more catalyst than recommended on the label, so increase the catalyst by the number of parts thinned or more. Don't worry about using too much catalyst with this recipe.
*
Lets say you're mixing up 1 gallon of this stuff - 4, 6, or more parts acetone to 1 part resin. For the purpose of calculating the amount of catalyst to use, treat the gallon as pure resin. If the catalyst bottle says to use 1oz for a gallon of resin, then use 1oz for your gallon of waterproofing sauce. Then give it a few more squirts for extra measure - again, excessive catalyst is not a problem when the resin is diluted like this.
*
Too much catalyst is only a problem when applying thick - un thinned amounts of resin - fiberglass application for example. Too much catalyst can cause so much heat that the resin becomes brittle, and that would be a structural compromise of the resin. We don't have to worry about that here:
• This is not a structural application like resin on fiberglass.
• Our resin is so thin that heat build up is not a problem.
With your first application done, it's time for some more. Mix up more of the waterproofing solution, this time using less acetone, and less catalyst. Apply, and repeat, reducing the acetone dilution each time. You will know when you've got enough coats because you will not see any coloration changes that indicate acetone soak-up is occurring in the wood - wallah! it is sealed.
*
You're not looking for any thick buildup of resin here, but more appropriately, the thinnest (least brittle) amount you can. You should still be able to easily feel the texture of the wood or concrete. All you've done is get the acetone to draw the resin into the pores of the wood, or whatever material you are waterproofing.
*
Your final coat should be done with waxed or finishing resin. Or, you can use the cellophane kicking method described above. The cellophane method of kicking resin is nice, because you will not need to remove the finishing wax with sanding or messy acetone wipe. But if you intend to paint, you'll need to sand the surface anyway. Just use the waxed resin and sand the surface when ready.

[JFerguson]

Originally Posted by SilverHoot

I copied this text from some boat building web site (I'm trying to find it now). I have not tried this but sounded interesting. Here's the text:

[I]Start with a small amount of resin (depending on project size) and thin it down with 4 to 6 parts acetone until it's almost like thick water. This is the secret, because the acetone will soak deep into every one of the most microscopic pores and fibers of the wood or other material. It really soaks in, carrying the resin with it. It's application is so light and thin, that it tolerates wood flexing without problem. It becomes an integral part of the wood or concrete and it will not crack or separate.
*
You'll need to use far more catalyst than recommended on the label, so increase the catalyst by the number of parts thinned or more. Don't worry about using too much catalyst with this recipe.
*
Lets say you're mixing up 1 gallon of this stuff - 4, 6, or more parts acetone to 1 part resin. For the purpose of calculating the amount of catalyst to use, treat the gallon as pure resin. If the catalyst bottle says to use 1oz for a gallon of resin, then use 1oz for your gallon of waterproofing sauce. Then give it a few more squirts for extra measure - again, excessive catalyst is not a problem when the resin is diluted like this.
*
Too much catalyst is only a problem when applying thick - un thinned amounts of resin - fiberglass application for example. Too much catalyst can cause so much heat that the resin becomes brittle, and that would be a structural compromise of the resin. We don't have to worry about that here:
• This is not a structural application like resin on fiberglass.
• Our resin is so thin that heat build up is not a problem.
With your first application done, it's time for some more. Mix up more of the waterproofing solution, this time using less acetone, and less catalyst. Apply, and repeat, reducing the acetone dilution each time. You will know when you've got enough coats because you will not see any coloration changes that indicate acetone soak-up is occurring in the wood - wallah! it is sealed.
*
You're not looking for any thick buildup of resin here, but more appropriately, the thinnest (least brittle) amount you can. You should still be able to easily feel the texture of the wood or concrete. All you've done is get the acetone to draw the resin into the pores of the wood, or whatever material you are waterproofing.
*
Your final coat should be done with waxed or finishing resin. Or, you can use the cellophane kicking method described above. The cellophane method of kicking resin is nice, because you will not need to remove the finishing wax with sanding or messy acetone wipe. But if you intend to paint, you'll need to sand the surface anyway. Just use the waxed resin and sand the surface when ready.

Just a word of warning when you mix the catalyzer aggresively like this sometimes the mix heats up a lot more than expected. Not all the time but every once in awhile you hear of it even starting fires. It's a good instruction and I would use it but I wouldn't mix it in the garage if you know what I mean.

[Melody Ranch]

Really Guys....I mean no offense here...but, I think your getting a bit anal on this floor prep. From what I understand this is just an installation of a floating floor over the original. The only place a leak will be a problem will be from the side walls and maybe down a wall from an upper leak. Water proofing the side walls can't be done from the inside. Its either done at the time of floor replacement or seam sealing outside. Wall leaking from windows or seams is corrected by window seals and seam sealing. As far as I'm concerned all this other epoxy, linseed oil, Thompsons, etc., etc., is like a fart in the wind. A good quality porch paint will preserve and prep the floor surface for a floating floor application. If the original floor is rough and worrysome to you...an inexpensive overlay of Luan is easy to install for that smooth base under a linoleum floor...
and even that is not necessary under the more rigid "click" flooring like Pergo.
I did try something ...strictly an experiment...on both a Pergo and an Armstrong floating plank floor. I filled the perimeter expansion space with a clear silicone bead, hidden under the base board, thinking it would still provide expansion capability and seal the floor edge surface from spilled liquids.