I have a shop with a 10x10 room inside I want to completely waterproof, so that I can wash parts and things and spray water around inside. Kind of like a giant shower. The room has a plywood floor and OSB walls. I have caulked all the joints and was going to paint the walls and floor with a heavy layer of exterior oil based primer and white paint.

But now I've started thinking about using some sort of roof coating, such as this:
Henry 4.75 Gal. 287 Solar-Flex White Roof Coating-HE287SF871 - The Home Depot

Do you think that might work better for my application? Can that kind of stuff even be painted on a vertical surface without running down? Could something like that be applied to bare wood or do I need to prime first?

Also, how well would that hold up for the floor? I was going to use a heavy coat of oil based porch/floor paint, but this stuff might seal it up a little better. Would it hold up to any foot traffic?

 

Just never in a million years going to work.
The walls could be done with fiberglass panels at any Lowe's of Home Depot but that floor would have to be a concrete and or tiled floor with the floor tapered to a drain.
What's that plywood floor installed over?

 

It will work just fine. The only real question is will it stick to bare wood and will it stick to vertical surfaces?

As for a painted, sealed wooden room, there is no issue. It is not meant to last forever. It is not meant to be a commercial kitchen. And most importantly I am not going to spend thousands of dollars. It's just a cheap temporary work room in a shop. I could just staple up some 6 mil plastic on the walls and be done with it but I don't want to look at that.

Drain is already installed, the final floor will be plywood with a waterproof coating. Let's keep this topic about waterproof coatings please. It's not really much different than a porch exposed to the weather. Absolutely no need for concrete/tile/fiberglass panels. It would be nice but there is no reason to spend that kind of money on this project. Sometimes you gotta think outside the box.

 

You are determined to do this. Why ask us? The coating you refer to won't take much foot traffic, and definitely not vehicle traffic, or even lawnmower, tractor traffic. You may not have a problem with it adhering to the walls if properly primed. The floor will be your nemesis.

 

They sell elastomeric coatings for walls [exterior masonry] and I have used elastomeric a time or two on the interior to hide cracks [cheap rental repaint] but have never heard of anyone trying to use an elastomeric coating on a floor. It dries too soft!! and would wear away in no time.

Your original plan is better but like Joe stated, it still isn't a good plan. To make a room waterproof for your intended purpose it needs to start with the construction materials!

 

I never asked if I should build a room this way. I asked if elastomeric roof coatings will stick to wood and vertical surfaces. Like I said, let's please keep this topic about waterproof coatings and nothing else.

To say "Just never in a million years going to work" is ridiculous, sure it will, and there are lots of different kinds of waterproof coatings available. I was simply asking about one type that happens to be really cheap and easily available. I could use bed liner type material, or fiberglass mat and resin, or a heavy coat of varnish, or a heavy coat of paint. All of those things would easily protect OSB walls from water. There are so many different things I could use it is hard to choose.

If roof coatings won't work for the floor that is not a big deal, porch and floor paint will work just fine. Or epoxy if I want to spend a little bit more. It won't last forever, but it doesn't need to. It's no problem to keep an extra can of paint around for touch ups.

Just because I asked a question does not mean I am stupid, or know nothing on the subject. I can have input too. Open your mind up a little bit. It's not going to make it into better homes and gardens, but that isn't the point.

 

Well, you may anyway when the subfloor rots out from moisture damage. Understand that the construction of a roof assembly is completely different from a couple of pieces of plywood setting on a floor. Wood floor joists expand and contract with changes in humidity, the plywood will also move with expansion and contraction. Anything short of a solid membrane will not be water tight. And as mentioned, these surfaces are not meant to be walked on. Even rubber roofs are limited in the amount of foot traffic allowed.

So, a product designed to pretty up an already waterproofed roof that is looking tired from the elements, is not to be taken as a one stop waterproofing membrane for any surface. My suggestion would be to set up a spray booth in a corner that will allow you to contain the water and use a pond liner to help corral the water and move it to an integral drain.

Everyone so far who has commented including myself are contractors. We regularly build shower enclosures that have to be 100% water tight. We also have seen the damage a small drip can cause to both plywood and especially OSB. Good luck with your project.

 

I've never applied elastomeric roof coating to anything other than a roof but have applied 1000+ gallons of masonry elastomeric paint to exterior walls. It is formulated for masonry but will adhere to primed wood. As stated earlier - it will not hold up to traffic.

 

So maybe it won't work well for the floor. Anybody have a specific reason why it would not work for the walls, at least as well as paint would?


Well, I'm an engineer, so I guess I've got them beat.

You got me. In ten years, I might have to replace the plywood. Maybe. What is that, $100? I'm not concerned if the entire thing rots out, like I said, it's in a shop, and it's somewhat temporary.

And hey, since you gotta bring up showers, I know a guy with a shower in his shop made entirely from OSB and plastic tarps. It's ugly as hell but one thing it is not is rotten. The shower pan is completely made from OSB and caulk. It won't last 100 years but it serves it's purpose in a shop just fine.

Believe it or not, they even make boats out of plywood. I'm not aware of anybody that makes boats out of OSB but that's only because it would be ugly. They make waterproof plywood boats all the time. There are lots of membranes that can be laid on top of wood, and elastomeric coatings are one of them. Plywood decking is also used on flat roofs all the time. One of the most common uses for OSB is roof decking.

The issue with that is unless the liner goes all the way up the wall, there will be a seam that needs sealed just the same as plywood or anything else. Or, even if I lined the entire thing with FRP sheets there is still seams that need to be sealed. I could just staple up some plastic but I don't want it to look that bad...

 

Not necessarily, I've painted a lot of new construction homes for engineers. Many of them fail to understand the different parameters that involve home construction. Some of the rocket scientist were the worst.


It's not just the sub floor. The moisture that the floor may suck up can also damage the joists and whatever else might be below it, not to mention mold

A boat is totally different from a room or even a shower stall. Your friend's tarp lined OSB shower stall will fare well until the tarp leaks.


An oil base enamel will give you the best protection against moisture but it will fail at some point and when moisture gets under the paint the real damage begins.

 

It's not lined with anything, only painted, I'm not sure what he used, but if I had to guess I would say whatever leftover paint he had.


At that point I can either repaint, or replace the sheets of OSB, it's not a big deal.

Just to be clear, the rest of my shop has a plywood floor, where I park vehicles, with dirt on their tires and puddles of water dripping off from rain or snow. The plywood is completely unfinished. It gets wet, and then it dries again. It's a little rough, but after 5-10 years of abuse I can just put down another layer. It has gone on this way since 1905, still not rotten, or moldy. The floor is about 6 different layers of 3/4" boards and plywood at this point...

 

This thread is becoming quite unproductive if all you are going to do is give a snarky comment back about every point being made. It is somewhat childish and certainly not carrying on a conversation.

Understanding how to build a waterproof shower will allow you to do as you propose. There are ways to fold membranes in the corners so that there is no seam basically creating a rubber bath tub that can not leak (run the liner a foot up the walls). The vertical wall liner is then cascaded down over the lip of the rubber tub so that all water sheets toward the liner and can not seep into the wall/OSB behind it.

 

What points being made? All I see are a few know-it-alls who cannot think outside the box. You're all making a lot of assumptions that are totally incorrect and giving advice on subjects I never asked about. I don't appreciate that, to say the least. It is not helpful to anybody.

Furthermore, if you are so stuck inside the box that you think a sheet of OSB cannot be waterproofed, I feel sorry for you, and you have no business posting in the "waterproofing" section here. Anything can be waterproofed with the proper coating. You could sheath your house in cardboard if you painted it with the proper product. There are MANY different products available for this in 2015. The substrate behind these liquid coatings is little more than a form, it could be anything.

As an example, here is a similar, but more expensive water proofer that literally lists "OSB" as one of the uses, right on the can!
Ames® Block & Wall Liquid Rubber Paint (BMRF5) - Roof / Foundation Coatings - Ace Hardware

I'm sorry I asked, I thought a forum about water proofing wouldn't be so stubborn. I know there are coatings that will work just fine for this, I was just asking about one that happened to be really low cost. I'll post pics when I am done so you can see how well it works. I don't need any further help.

I did say I could just staple up plastic, but I don't want to do that, over and over...

PS - your job title is not relevant on the internet, nor does it automatically make one good (or bad) at what they do.

 

Not in my book. I have had to correct too many engineering mistakes on blueprints because the engineer never got off his duff and visited the jobsite, then swore it would work. I agree with Z that the thread is getting a little snarky. I'll leave the rest of you lowly contractors to it.

 

I have an engineering degree although I have never worked under it. One thing that I have noticed is that the vast majority of mechanical engineers are arrogant know-it-alls that never worked a day of their lives in the real world. I've worked far too many jobs where I had to come in and fix several mistakes made by degreed engineers that might know theory forwards, backwards and upside down but knew absolutely nothing about what happens in the real world.

Just tonight I was talking on the phone with a former work partner (he's still working) where the lack of a motor temperature monitor caused a variable speed drive to smoke a 600 horsepower motor. The engineer who designed the system stated the motor didn't need the temperature monitor because the VFD had a temperature "profile" that assumed the temperature. Worst thing is, the motor DID have the requisite RTDs (Resistance Temperature Detectors) as standard so a monitor would have only been a few hundred dollars more and would have saved the motor.

So while I agree with Number21 that you CAN seal almost any material against water I also agree with everyone else that no matter what "sealer" is used it will eventually fail, more likely much sooner rather than later. But if Number21 doesn't mind doing the job over rather than doing it correctly the first time, who are we to tell him differently?

I'll also tell Number21 that his postings are absolutely classic examples of the person that has already decided what to do and is only looking for someone to sprinkle the holy water and bless his project. Sorry, but you won't get that at this forum.

 

Couldn't have said it better Primer, caulk and paint can seal most any substrate but will never be a long term solution. Often it's best to bite the bullet and go with a method that will hold up long term. Doing it right is almost always cheaper! Materials to keep redoing a job will add up not to mention the labor involved.