Fiberglass & resin steam shower walls construction sound??

Hi,

Sorry I have an odd question/situation about fiberglass resin usage:

Remodeling our bathroom installing a steam shower.
To meet our artistic and unconventional desires, our handyman was certain he could create interior shower walls using plywood and the plywood covered with bondo fiberglass cloth coated with liquid polyester resin from home depot and silicone caulk the wall seams.

Additionally this would allow random single pages from a book to be placed on the wood under the cloth so it could be slightly visible through the resin for a unique look.

Our handyman created the shower wood walls but then his health declined and can no longer work.
I don’t remember what kind of plywood grade he used.
He did install plastic sheeting between the wall studs and the plywood.
The fiberglass and polyester resin has not been purchased yet.

We are talking to a new handyman about finishing the job and he is uncertain such a wall covering will be sound over the long run.
Before he attempts to finish he asked us to investigate this further.

So I know this may be unorthodox but Any input would be great please!
I’ve asked a shower forum with no response.

I see it appears this system is used on wooden boats, so very similar…..

Q’s that come to mind:

1. Might this wall design be reasonably sound for this application?

2. Should the wall design use the fiberglass cloth or the fiberglass matt or I see bondo has a fiberglass strands filler, or should no fiberglass reinforcement at all be used for these walls?

3. Is the polyester resin hard to apply on vertical walls, I see bondo has a jell formula for vertical surfaces, should we use that?

4. Will the random single pages from a book interfere with the adhesion?

5. At what stage should the single pages from a book be installed into the fiberglass & wall resin buildup?

6. Is there a better suited product than bondo from home depot?

7. Is there a better final finish coat to use?

8. Will the finished surface be smooth enough to resist mold, mildew, soap scum etc?

Thank-you for your time!

 

Welcome to the forum Jim.

Your handyman wasn't particularly familiar with the materials he envisioned using and it's likely a good thing he's no longer on the project.

Bondo and other polyester products aren't well suited over wood, especially in the environment you plan. They just don't stick all that well. Bondo will be opaque and obscure anything under it. This is a material to fill dents in car doors. Bondo is a brand name, though to us, most common associated with their filler products, they also sell polyester resin, hardener, etc.

It can be done, though plywood wouldn't be my substrate choice. Lowe's/Depot sells sheets of 'glass (GRP), used as surround material in bathrooms. This will take polyester very well (it's also polyester). It would be used much like plywood, though isn't very strong, so would need to be glued to a structure for support.

The pages would be put down first in a wet coat of resin, which will adhere them to the substrate. Of course, if the pages are two side printed, the reverse side will likely "bleed" through, unless the paper is quite thick. Some simple tests for page bleed would confirm this possibility.

Durability over the GRP panels at the big box stores will be good, but this isn't an easy job, if you've never played with goo and vertical surfaces.

Mold and mildew are environmental condition specific, which can be controlled (humidity, ventilation, etc.). Soap scum, well there's nothing I know other then scrubbing with something occasionally.

 

Like many others doubtless, my bath is a GRP moulding. No problems with it over the last 6/7 years. Reasonable quality Swiss made unit with good quality gelcoat and resins by the look and feel of it. As I installed it I got to know it quite well.....I'll spare the fact that the old one was imperial and the new one metric and a bit longer so the hard block walls....etc

Personally if I was trying to get the 'look' using semi transparency, I would be OK with a clear gelcoat. However I'd do as much horizontal as possible as panels that you can work on and bond together later or at least minimise the vertical element. It is a lot of work going the 'wrong' way round on a laminate ie from core to surface. Do not underestimate the cutting time if you go this route.
Be aware that different manufacturers gelcoats usually have a tinge colour ie pink, yellow, green so select that transparent one carefully.

 

I wouldn't use any plywood anywhere in that project. You might get away with recorcinol glued all hardwood panels, but you are talking way expensive stuff. As the wall heats up it will try to outgas and cause delaminations. You want a very good solid plastic shower enclosure as a starting point, or a proper ceramic tile job, and I'd back it with half inch concrete board sealed only on the shower side. And treat all the framing behind and above with a preservative before hanging the sheeting. Copper naphthenate is a common one, but not everyone is enamored by it. You should buy specially rated lighting fixtures as well. Preferably ones that at least make an attempt at being vapor proof.