Waterproofing Plywood

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beiland

Active Member
#21
by jimfitch on another forum....

I would say a winner is a product that works, seals the wood from moisture expansion and contraction, and hopefully doesn't cost an arm and a leg.
I did some quick searching and found this which looks cheap and cheerful:
Olympic Water Guard - $10.48 a gallon. Cheaper than the above and looks pretty good.
1530918608323.jpg

Most customers used it on their deck, which is subject to a lot more harsh sun and rain. Looks like that will be good for bench-work wood to help it resist expansion and contraction. My wood is all being stored until ready to install in my basement, which is being kept around 55-60% humidity with a de-humidifier:
https://www.homedepot.com/p/Olympic-Waterguard-1-gal-Clear-Multi-Surface...

Product Overview
WaterGuard Multi-Surface Waterproofing Clear Sealant offers convenience and value. Penetrating, advanced multi-surface sealant protects against water damage and creates a mildew-resistant coating. Perfect for a variety of substrates including concrete, brick, stucco and wood.
  • Ready mix, ready to use clear sealant
  • Provides protection on multiple exterior surfaces, including: exterior decks, fences, siding, wooden furniture and structures, concrete, brick, stucco, steps, sidewalks, patios and more
  • Durable sealant that provides waterproofing protection
  • Penetrates and protects against water damage
  • Provides mildew resistant coating
  • Clean up with just soap and water
  • Normally dries in 12-24 hours when applied at 50°F to 85°F
  • Allows wood to weather and gray naturally
 

Selector

Active Member
#22
Such products offer a high surface tension on which water can be expected to bead and to run off. Think polymers like wax and urethane. Think Gortex which water can't penetrate, but which allows your evaporating sweat to works its way, molecule-by-molecule, out through the micro-pores of the material. I don't know that the liquids offer impermeability to moisture, which is another kettle of fish. Moisture is a single molecule of water, perhaps several of them adhering to each other, but still much too small to be seen even with advanced microscopes, except for perhaps the electron variants. Whatever this person uses, it must not be the least bit porous, it must perfectly cover the entire surface of the material he wishes to protect, and there can't be any mistakes. Even screws and nails driven into the material through this NASA-perfect coating will allow moisture to enter the wood over time unless the room humidity is controlled somehow.
 

Sirfoldalot

Plucked Tailfeathers
Staff member
#23
Sigh....
All I needed to see was the last line in the "product overview".
Like has been said many times, "It's your RR". I am sure that it will be fine.
Hope everything works out for you.
 

beiland

Active Member
#24
Timber Pro Stabilizer

BlackAdder
Over many years of outdoor projects, pine, cedar, and fir furniture, fences, and chicken coops I've used many 'water seal' products. All have needed to be resealed over time. This product (https://timberprocoatingsusa.com/products/internal-wood-stabilizer/) is amazing. Over six years of use and I've never had to reseal or found any rot. Because it worked so well outdoors, I used it in building my present benchwork. It might be worth a look or give the company a call and tell them what your doing.​

Thanks for that reference. I wrote them an email today.
 

Iron Horseman

Well-Known Member
#25
I'm building a layout in a shed external to my house in the hot, humid state of FL. While I have the shed under a carport and insulated well, it does seem to remain cool for the most part. But I do not intend to run the AC full time, so it will experience temp and humidity swings.

Many of my decks/shelfs will be good grade, multiply layered 3/4" plywood, which I intend to try and 'seal up' as much as possible against moisture absorption, and the subsequent warping that can occur..
Any reason don't you don't just use pressure treated plywood to start with? It has already been saturated with water proofing rot and fungus control.
 

Selector

Active Member
#26
I believe he is mostly concerned with dimensional changes across the grain due to high humidity, not so much with corruption of the material.
 
#27
Late to the discussion, but why not just use -

1) use exterior grade plywood
2) use marine grade plywood
or
3) MDO (Medium Density Overlay) this is the stuff almost all the traffic direction (think green) signs are made of.
 



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