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Water/weather proofig plywood

Started by D2 Cody, January 31, 2018, 10:10:54 PM

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D2 Cody

Hi guys,
I was wondering what is the best way to treat plywood. Not the osb particle type but the regular smooth plywood. I built a pretty neat over the wheel well type chainsaw box with 2x4 framing and plywood body to keep my cutting supplies in and don't want it to become ruined the first year it is in the truck as it took a little money and time to build It. Any advice would be greatly appreciated.
Are you just going to lay there and bleed or get up and do something about it..Wyatt Earp Tombstone

Echo-Stihl-Caterpillar-Dodge-Craftsman-Lincoln

Texas Ranger

spar varnish, but it will break down and need frequent treatment.  Or, treat it like a counter top and use a glue on water proof material.  Unfortunately, nothing is perfect, nor last fore ever.
The Ranger, home of Texas Forestry

PC-Urban-Sawyer

A good quality exterior paint will last the longest...

Herb

WDH

Here, you can buy pressure treated plywood.
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

Bruno of NH

I built over the rail top boxes for my work truck 8 years ago and sprayed the black bed liner on them
They have held up great :)
Lt 40 wide with 38hp gas and command controls , F350 4x4 dump and lot of contracting tools

isawlogs

 The box is made and you want to put something on it to protect it, not wanting to bust any bubles but no matter what you do to it, some water and moisture will get in there and the regular plywood will diteriate. When doing things like that, I would you marine plywood.  ;)
A man does not always grow wise as he grows old , but he always grows old as he grows wise .

   Marcel

Bruno of NH

I used the sign plywood with the facing on it and advantec plywood for the bottom
Lt 40 wide with 38hp gas and command controls , F350 4x4 dump and lot of contracting tools

D2 Cody

Guess I'll try the bed liner as that was my first thought to and with the weather strip around the opening panel I think it should work fine for years. Also might take uncles sheet metal bender and build a case I can just slide over the top and take on and off when I need in it. Thanks for the replies that gave helpful info.
Are you just going to lay there and bleed or get up and do something about it..Wyatt Earp Tombstone

Echo-Stihl-Caterpillar-Dodge-Craftsman-Lincoln

woodworker9

 If you used an interior grade of plywood, it was laminated using interior use only glue.  No matter what you do, it's going to delaminate, unless you encapsulate the entire project in epoxy/fiberglass resin, like a boat. 

Even if you coat it with several coats of pain/spar varnish/marine products, etc.....the glue inside is still going to eventually fail.

Next time use marine grade plywood or MDO.  Both are made with exposure to the elements in mind.
03' LT40HD25 Kohler hydraulic w/ accuset
MS 441, MS 290, New Holland L185

ponderosae

I was just expirimenting with the idea of smearing water-resistant glue on untreated plywood or dimensional lumber, for an outdoor shelf where I don't care about what the finish looks like underneath (because I already have the glue, and want to see if it's useful for other things). This was for some little nailer plates I glued on top of concrete pavers with PL Premium construction adhesive (which says it is water-resistant). I also had some Titebond II wood glue, which says it has "excellent water-resistance", so I tried spackling a layer of that on the sides of the wood plates with a putty knife.

Well, after the glue dried for a few days, and then some rain fell on the wood, it looks like the Titebond does not have excellent water-resistance, at least when smeared on the outside like that. It simply gets wet, and turns soft and white, like human skin might at times. Then I can scrape it off easily too. The construction adhesive, on the other hand, does appear to have excellent water-resistance, where I left that gobbed out between the wood and concrete, and its properties don't change when it's rained on (that stuff only comes off with a chisel).

I'll have to try smearing a layer of construction adhesive over the wood now, since I think it will work there too. Time will tell, but I don't expect there to be any short term issues at least. They say it isn't recommended for continuous water immersion, but I think it will make the wood surface water-resistant for an occasional rain soaking.

doc henderson

water resistant means a spray of water, and not long or continuous exposure.  tite bond 3 is more resistant than 2.  epoxy can work and with a little fiberglass help it hold up.  my brother in law does bed liners and sprayed his whole utility trailer.  stuck to the metal but peeled off the wood.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

ponderosae

Right, I just think it spoke for itself how water-resistant those appeared to be by comparision (one much more than another). Especially when the one that didn't work says in bold print on the front of the container that it has "excellent" water-resistance, and is "ideal" for exterior applications, this implies that it would work better than with a light misting in foggy weather only.

Well shoot, I don't know how old this wood glue was, but it worked okay indoors. Of course, it didn't stick to the other glue, which had dried before I applied that, but I'm sure it didn't resist water when already dry on the bare wood itself, anywhere that it was splashed repeatedly, including on a post where I put some of it lightly around a knot, and there was no chance of the other glue or concrete interfering at all there (I could just rub the water logged glue off with my finger). Some of the glue was harder to scrape off in places as it dried again, but I think it was also trapping water behind it in the meantime.

Anyway, I'm not recommending the other glue either, I just think it's worth a try, since it seems practically waterproof and I have enough extra for that. Beyond my own observation though, another clue about it having good water resistance comes from this data sheet, where the stone bonding compression shear strength is higher after it is immersed in water for 24 hours, following a long cure time. For instance, they say that the polyurethane connection of Fiber cement to Douglas Fir plywood is 305 psi after a 7 day cure, and 377 psi after a 14 day cure followed by water immersion and drying. So maybe the construction adhesive can get stronger after being soaked, which could mean it holds up pretty well with the average rainfall. They say it is "waterproof" for interior and exterior applications, but not recommended for submersion applications (and another technical datasheet says both waterproof and water-resistant, which seems to mean it's usually waterproof unless under water pressure). Well you never know...

Don P

Once water gets behind it the wood cannot readily dry, the door swings both ways there, creating a composting bag.

ponderosae

Yeah that may be (if water can get in there). In my case it's mostly covered, but the rain still splashes up off the ground, so it would probably not flood it enough to get trapped under there (as long as the glue didn't absorb it). I think some of the marine paints are similar (involving urethane), just not as thick. Isn't the idea with those that water cannot penetrate the wood (or at least not nearly as often)? From what I've read, treated lumber isn't waterproof anyway, so it all has to be coated with something or be a more oily wood to begin with.

Don P

 :D, When did we go from untreated to treated here?

With untreated wood and a film forming finish, if the finish cracks or has holidays, bulk water gets behind the finish. That raises the moisture content of the wood potentially into the rot zone. In order for the wood to dry that moisture needs to leave as vapor, a lot of vapor has to pass back out through that small breach in the film, not dang likely. So the moisture content rises with each rain until rot sets in. If you keep it painted with a good film it works fine. Wood also moves which tends to create those cracks in the finish.

Treated wood does not decay readily even if wetted. It does check with repeated wet/dry cycles.

It is a good idea to put a water repellant coating on either to repel bulk moisture but one that lets water vapor back out is not a bad idea.

ponderosae

Well, the topic sentence was about the best way to 'treat' plywood for water/weather 'proofig'. Okay, as far as the 'figs' go, the figures on the wood myths page say that "Pressure treating does make wood rot resistant. But — it doesn't make wood water resistant. Pressure treated wood still soaks and looses moisture. And as a result, the wood moves, cracks, twists, bends, cups and virtually tears itself apart." So if it can be waterproofed, it wouldn't tend to bend and crack the coating to let water in, because that tends to happen from it not being waterproofed. Of course it's possible (and more likely on something like a floor span that it would be flexed with ordinary use), but I don't think they would waterproof boats if it really caused more trouble than it was worth to heavily coat the wood.

Simply letting wood soak up water and then air out doesn't work around here. On a pair of steps, for instance, the side board that was rained on has totally deteriorated, even though it had been painted with an exterior coating (which probably cracked from it letting the wood get wet repeatedly). The other side that was part way under a roof didn't deteriorate, so it was all about it getting too wet on the uncovered side.

doc henderson

Lots of good comments and questions.  by the way, where are you from and what is your day job?  I understand pressure treated to be rot resistant due to chemicals in the wood that stop certain organisms from eating the wet wood.  cotton wood will rot with soil contact, but up off the ground and repeatedly wet it will last a while.  marine grade plywood uses waterproof glue, so it soaks up water but does not delaminate as a result of getting wet.  boats get enveloped in fiberglass and resin and if water does get in, the inside wood will eventually rot, and sometimes dry rot.  I think it takes moisture and wood degradating organisms to rot wood. some bracing in smaller sailboats are just cardboard to stent up the fiberglass until it cures.  water proof is a lot more than water resistant, and may not even truly exist in the wood world.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

ponderosae

I guess a splash board could work too in some cases, right now I have plastic bags draped in front of there so it will dry in the rain. That made me think of putting a sacrificial splash board in place of the plastic, which would be easy to replace if it deteriorated, while the rest of it would stay dry. I can even try coating that with glue as an experiment, since it's trial and error in my book.

doc henderson

do you pictures of what you are trying to protect?  I have been making generic comments but may be some other advice based on what you are building.  cheers
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

doc henderson

I made a planter for my wife.  fiberglass and resin to the inside.  the inside looked the same after 3 years of wet soil and plants in it, but the out side failed with trot and a leg that broke off.  the wood of the box was honey locust.  not sure what surface area amount you are dealing with, but could be cost prohibitive.



 



 

just lined the inside of the planter.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

ponderosae

QuoteThe planter... and pictures of what you are trying to protect?

I like your planter design, it's very crafty.

Some pics of the kind of area I'm working in and issues surrounding that are on the splashback damage page here. I'm thinking that a slanted board will simply keep the rain from splashing back onto my shelving supports (which are in front of the siding), and I'll probably experiment with the polyurethane on that to see how well it repels splashback, rather than letting it puddle up on the support plates (I was surprised how much water gets back there a couple feet behind the eves, and splashes up to a couple feet high, but never noticed that before).

doc henderson

If the water is "splashing" off the ground, some pea gravel could dissipate this.  I use a lot of spar urethane with uv protection.  I use minwax.  some will spray a Thomson water seal protectant like product on high splash area.  it is wax based and helps keep things cleaner as well, but will need reapplied.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

ponderosae

Yeah, well there's either some concrete there or things like trash cans have to be rolled on the ground, so I can't put gravel down. I don't think the splash board will stick out farther than the shelf though, so it should be out of the way enough to be a reasonable set up still. I'd like to find out if the polyurethane works as a surface coating mainly because I use it for joints anyway, and typically wipe the extra off, but maybe I should be spreading it around more for outdoor framing. I'll have to see...

ponderosae

Quote from: doc henderson on October 17, 2019, 10:29:02 PM
marine grade plywood uses waterproof glue, so it soaks up water but does not delaminate as a result of getting wet.  boats get enveloped in fiberglass and resin and if water does get in, the inside wood will eventually rot, and sometimes dry rot.  I think it takes moisture and wood degradating organisms to rot wood. some bracing in smaller sailboats are just cardboard to stent up the fiberglass until it cures.  water proof is a lot more than water resistant, and may not even truly exist in the wood world.
I looked up some info on that to learn a little more, and although the glue used in marine plywood is different, the one-part polyurethane in construction adhesive is like what they use for "topside paint" on boats:



Quote"A topside paint is any paint you apply above the waterline anywhere on your boat. This includes the sides of the hull, deck, and interiors. Marine topside paints are commonly one of the following types: one-part polyurethane, two-part polyurethane, and alkyd marine enamel. There are also buffable, two-part acrylic urethanes.


• They're resistant to moisture and abrasion, and are very durable.
• They have the flexibility to withstand hull expansion and contraction.
• They're designed to resist exposure to both direct and reflected, water-intensified ultraviolet light, maintaining color and finish..."
So it would seem to work well there, since it is expected to get wet regularly and protect the wood on a boat deck, etc. They say the one-part is a DIYer's dream paint for the boats, and more flexible than the two-part. Another site says the one-part polyurethane is the most popular topside and deck paint choice as well. It's more like weather proof vs water proof, but those are pretty much synonymous on land methinks. You know, just because it isn't waterproof at twenty-thousand leagues under the sea doesn't mean it isn't going to be rain-proof at sea level (unless maybe you're building something in a flood zone, or anywhere it would tend to puddle the water).

I'd prefer to deflect most of the rain anyway, because it will keep it off all the siding there, and I don't really like to work with glue so much or pre-paint either. But I'd at least try coating the bottom area where my deflector would contact the ground or get splashed a lot. I usually use the construction adhesive as a kind of liquid shim where I'm working in non-square areas or reinforcing pieces that I don't want to split with fasteners, and it's good for bonding multiple materials. So it would probably hold up on the surface too. Although there could be a lot of little anomalies in plywood to fill in completely with that or paint. I haven't worked with the paint, but the adhesive can be slathered on really thick like peanut butter there, and expand to fill in cracks or knot holes, so that could do the trick, I guess. Well, there's nothing to lose with it getting wet all the time but a piece of plywood either way, or maybe not...

Otherwise, if anyone still thinks it's a weird idea, I found it weirder to read about people soaking wood in used motor oil, and am going with the following opinion on that:
Quote"So, here is the reason that fishing boats out of San Francisco had their decks oiled with motor oil. It was used for two reasons. One was to prevent fish blood from soaking into the wood which makes for a very stinky boat! It was cheap and so they used it. In addition, many of the fir decks were tight seam planked and burlap bags soaked in sea water were used to cover and keep the seams tight when the boats were in port. Motor oil has a tendancy to retain moisture which kept the decks tight as well. But, as I have noted before, petroleum based oils do not prevent rot, THEY WILL SUPPORT IT! This is the reason that diesel oil must be treated with a fungicide in order to prevent fuel tank contents from from turning to Jello! Any time someone tells me how oil or tar prevented rot in their boat, I look to the kind of material it was use over. More often than not, it is the quality of the wood and not the petroleum based product that kept the structure sound."


sail_smiley

Nebraska

I would have to try coating the box exterior  with pine tar paint and seeing  how long it would last. I wonder if coating the inside with paint on bed liner would be helpful to protect it from  bar oil and the like. 

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