How do I weatherproof plywood?
- Thread starter jgelack
- Start date
BORING HOP YARD
Well-known member
I have never done it but I have seen people use fiberglass resin and saturate the plywood.
Good luck on your quest!
Good luck on your quest!
mike93lx
ALLIANCE MEMBER
You could just use pressure treated plywood
ez-duzit
Well-known member
Polyester resin would be a cheap, but poor choice for this. Penetrating epoxy resin, like WEST System, is far better, but requires UV protection, such as paint.
jack stand
Well-known member
First thing that comes to my mind is if you're building it, build it with a roof
billconner
Well-known member
start with marine ply?
Walkers
Well-known member
Simply have a piece of galvanized steel bent to cover the top.
acer66
Well-known member
OP says he is using exterior grade plywood.
Jakemedic
Well-known member
I used spar exterior varnish on a pine picnic table one time. It looked amazing for about a year. Went to recoat it, and it looked like ****. Maybe an exterior grade stain? but read the label, I did that once too, and the stain came off on clothes when sitting in it. Best advice is to go to a good paint store and ask. They should be able to tell you. Best of luck!
mike93lx
ALLIANCE MEMBER
Exterior grade does not mean constant exposure, especially on a flat surface
e36jon
Well-known member
Borntoolate
Well-known member
Just build it and seal it up as above. But I would make it easily replaceable.
When it does go bad, remove some screws, cut a new piece and screw it down. Done, all new.
Pressure treated with nothing else would probably get you 5 years +/- depending on your weather conditions. But the pressure treated lumber of today is of varying specifications and some of it ain't worth a ****. Marine grade is probably better. But you really need to look at the actual PT spec to really know what you are getting.
But if you are gonna seal it you probably can buy regular plywood. Seal the edges real well since they will wick water in the most and likely be the biggest issue.
When it does go bad, remove some screws, cut a new piece and screw it down. Done, all new.
Pressure treated with nothing else would probably get you 5 years +/- depending on your weather conditions. But the pressure treated lumber of today is of varying specifications and some of it ain't worth a ****. Marine grade is probably better. But you really need to look at the actual PT spec to really know what you are getting.
But if you are gonna seal it you probably can buy regular plywood. Seal the edges real well since they will wick water in the most and likely be the biggest issue.
billconner
Well-known member
It would depend what sort of work was being done on this table but spar varnish on marine ply and then attach a sacrificial surface - 1/4 ply, filon, or just least expensive 4 x 8 material at a big box store. Plan to replace it every other year. Meanwhile you can remove it for nice appearance, party use, and so on. Just a thought.
65ranchero
Well-known member
Won't that trap moisture under the cover?
Ext. plywood means the glue won't fail when wet. Pressure treated means bug won't eat it. Neither will protect wood fibers from sun and rain exposure. If you really want to seal it, lay fiberglass cloth over it and apply resin. (like building a boat)
theoldwizard1
Well-known member
True marine plywood (not the stuff they sell in big box stores) is INCREDIBLY expensive. It still should have a couple of cowts of epoxy. If exposed to the weather, even the epoxy will break down.
If you really want it to last for a long time, start with 5/4 pressure treated deck boards. Let these "season" for at least 6 months. Make sure there is weight on them so they don't cup/warp. Cut about 1/2" off each and glue them together with construction adhesive or TiteBond III.
Nthill93
Well-known member
Used motor oil works great on trailer decking don’t see why it won’t work here.
billconner
Well-known member
If the "work" was food prep, not sure the motor oil would be best. 
Maybe olive oil. (I think there's a Popeye line to come, or maybe I'm just really old, and of course that's oyl, not oil.)
Maybe olive oil. (I think there's a Popeye line to come, or maybe I'm just really old, and of course that's oyl, not oil.)theoldwizard1
Well-known member
Food prep means stainless steel.
billconner
Well-known member
for food for you and family?
strutaeng
Well-known member
For a work bench? Oil paint. It's going to get dinged I'm assuming...give it another coat as it wears, ages, etc.
Skiff Builder
Well-known member
This is a piece of three-quarter inch exterior grade CD plywood. It's been laying in the truck bed parked outside since 2017. All it has on it is one coat of urethane alkyd paint on the exposed side. The underside has not been coated. Don't overthink it it's only a work table. 
Skiff Builder
Well-known member
Here is an old workbench I have had for the past 33 years. It has lived outside over half its life. No coatings whatsoever. 5/8 inch exterior fir top and rough sawn eastern white pine legs. It gets a 60 grit sanding when too much **** builds up on top.
Douglas fir is a pretty hardy specie In my experience.
Douglas fir is a pretty hardy specie In my experience.Jacko264
Well-known member
Phenolic ply would be good it’s what is used in horse box floors
Graham
Graham
What a rabbit hole I entered researching how to protect marine plywood for trailer outdoors. This post caught my eye…. Below is the paper from Forest Products lab with good info:
quickfarms
Well-known member
What type of work is the table for and where do you live, at least a general idea to judge the weather and climate.
Personally I would look at the used restaurant equipment places for a prep table the size you need and not worry about waterproofing
Personally I would look at the used restaurant equipment places for a prep table the size you need and not worry about waterproofing
But epoxy resin, not polyester resin like one finds in most fiberglass repair kits at auto parts stores. Epoxy resin can be found a marine stores. Bring your checkbook.
Plywood is a poor choice for this application, because the veneers have an open grain and microcracks that results from shaving the veneer off the spinning log. Penetrating epoxy essentially turns the wood into a sheet of thermoset plastic that is far less hygroscopic. Dimensional hardwood lumber like white oak would be easier to protect by just rubbing it with a 220 sanding sponge and wiping "outdoor oil" on it once a year. Around here, white oak is used for fence rails and isn't too expensive for stuff like that.
Rick "dense tropical woods would be better but are much more expensive" Denney
I just wish I could find plywood made from good-quality Douglas Fir.Here is an old workbench I have had for the past 33 years. It has lived outside over half its life. No coatings whatsoever. 5/8 inch exterior fir top and rough sawn eastern white pine legs. It gets a 60 grit sanding when too much **** builds up on top.
Rick "good luck with that these days" Denney
steel 35
Well-known member
Outdoor high gloss polyurethane with UV protectio, mixed with thinner so it’s absorbed,
Very thin, kinda thin, then not so thin.
Very thin, kinda thin, then not so thin.
Prospecter
Well-known member
My horizontal wood surfaces are where I use up old paint, stain, and urethane. Kinda fun, because colors change periodically depending on what finish we are using up at the moment. I have trailers in red, orange, blue, and yellow at the moment. My benches have polyurethane on them. And it's all stuff I would have needed to dispose of or store.
this
cpttuna
Well-known member
I would try a 2 part epoxy
what sort of work table?
I might build the table with 2x treated material , make the plywood top easily removable & store it out of the weather when no in use
I might build the table with 2x treated material , make the plywood top easily removable & store it out of the weather when no in use
mark-NJ
Well-known member
I made just such a table a few months back. The frame was aluminum (old picnic table, wood slat top long ago rotted away). Made a frame with 2x4's to fit over it, and screwed a piece of 3/4" CDX plywood on top.
Next, sealed all of it with 2 coats of epoxy.
Next, covered it with 10 oz fiberglass cloth (left over from a boat I built), and put 3 coats of epoxy over that.
Lastly, 2 coats of enamel marine hull paint (also left over from the boat). This table will out last me.
This is a "i don't give a $hit" table for painting, fabricating, etc. Wife uses it for potting plants. There's already spraypaint all over it. Pure function, zero fashion...
EDIT: just realized that this was a one-year-old thread. Sorry fellas.
Next, sealed all of it with 2 coats of epoxy.
Next, covered it with 10 oz fiberglass cloth (left over from a boat I built), and put 3 coats of epoxy over that.
Lastly, 2 coats of enamel marine hull paint (also left over from the boat). This table will out last me.
This is a "i don't give a $hit" table for painting, fabricating, etc. Wife uses it for potting plants. There's already spraypaint all over it. Pure function, zero fashion...
EDIT: just realized that this was a one-year-old thread. Sorry fellas.
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