Exterior plywood - Woodworking Talk - Woodworkers Forum
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post #1 of 6 Old 09-12-2020, 03:43 AM Thread Starter
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Exterior plywood

So I have a project coming up that will be outside, but covered for the most part , but not entirely. Some areas may be exposed to weather. It's a little library for the neighborhood.
Here's the problem. I'm footing the bill since I volunteered and I have what I believe to be cdx, possibly adx though I'm not sure. Probably cdx since I really doubt any home center anywhere actually carries anything I'd trust for the A rating..Anyway enough for my cynicism for one day.. It's not going to have ground contact and I hope to have some decent exterior paint to protect things.

What's the best way to protect it just in case it's not exterior grade? The reason I ask is I want to use some old panels I already have, but I never really checked the ratings when I purchased it. I didn't plan at the time for any of it to be outside.
I'm going to trim it with hardwood, white oak, maybe cypress or even cedar. I just don't want anything peeling away like some plywood does with first contact with moisture.
I'm thinking a good exterior oil based paint and exterior glue should do just fine.
Any other suggestions other than lots of exterior caulking?
I probably need to dig up some roofing shingles somewhere. I obviously don't need a whole bundle so someone in the area is bound to have a few.

Hmmm..just walked through the shop and realized I'm really low on plywood. I've been going through a bunch this past summer. Back in May and June I had 8 or 9 sheets of 3/4".. I don't remember cutting up that much, but apparently I did since I only have a 3x3 sheet and a few odds and ends left.. I better check the laundry lint. I bet half of its in there!
At least I have my built in excuse to go buy some nice exterior grade plywood.. The old woman will go for it since it's for the library.
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Last edited by allpurpose; 09-12-2020 at 04:23 AM.
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post #2 of 6 Old 09-12-2020, 08:40 AM
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Waterproofing Plywood

when it comes to exterior projects, especially ones that use plywood,
I suggest a person look at "how to build a boat transom" or - "how to build boat seats".
these two items live outside in a pretty demanding environment.

I used to use a good grade B/C exterior grade pine plywood and sealed with a deep penetrating mix of a few items listed below.
with the advent of so much new junk plywood from other countries now, I am afraid to use it for myself, much less recommend it to someone else without knowing exactly how and where it was made. even the so called "marine plywood" is under attack with counterfeit products that will fall apart when wet.
(of course, the "go to" would be MDO exterior sign grade plywood).
anyway, you can mix up this concoction and test it on some scrap plywood and see how you like it. (this is just the waterproofing sealer - not the final finish).
and to add more confusion: there are literally hundreds of wood deck sealers on the market today. each saying they are better than all the rest. (so who knows).
what gets me is people pay thousands of dollars for a new wood deck, then waterproof it and seal it and stain it . . . . but, what about the bottom of the boards ??

Exterior plywood-waterproofing-formula.jpg

and after thoroughly sealing the plywood and flooding the edges, let dry/cure for a day or two. (3 or 4 is better). then force a quality exterior "paintable" caulk into the edges with your finger - let that cure according to the instructions on the product you use.
then - prime and paint like any exterior project.
Exterior plywood-caulk-seal-plywood.jpg

looking forward to seeing your project .

,

there is no educational alternative to having a front row seat in the School of Hard Knocks.

Last edited by John Smith_inFL; 09-13-2020 at 12:30 PM. Reason: changed photo
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post #3 of 6 Old 09-12-2020, 03:11 PM
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When i was a teenager, in the 1990s, and the bulls were in their heyday, i wanted to build a basketball backboard From scratch. My dad had some scrap 1/2 plywood left over from building his barn, that i could sandwich 2 together... i then coated it with THOMPSONS WATER SEAL, 2 or 3 times, on all sides, and then used some sort of rustoleum water based exterior paint to paint it white, and then the bulls logo... that back board was still up when i drove past my folks old hime a few years ago.... the paint was mostly gone, and it had weathered, but had a rusted chain net on it, and the current owners had restriped the key a few years previous. I knew it was the same backboard, because i had burned in my name with an electric iron thingy, before i painted it, and u could see it plain as day in the corner...
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I used to be fairly indecisive, but now....... I'm not so sure.
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post #4 of 6 Old 09-13-2020, 12:18 PM Thread Starter
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I got the go ahead from the notorious HOA (home owners association) and in the email it said, "Someone from the HOA will call you to discuss placement.." which to me means that if they don't like any portion of it for any reason whatsoever it ain't going anywhere that'll be remotely protected from the elements despite the fact that the HOA owns and operates a park shelter big enough to turn into a 4 bedroom house.. I'm guessing it'll end up somewhere in the corner of my backyard, but you never know. There's quite a few people in the neighborhood who seem quite enthusiastic about it getting made even if not a single soul has offered even a penny nail to help with the building of it.. Cheap bastrids.. lol

I figured it's time to change my signature so hold your breath. This is it.
Impressive, huh?
Marty or Marty Farty if you feel mean.
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post #5 of 6 Old 09-14-2020, 07:02 AM Thread Starter
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Well, here's the basic layout. Nothing unusual, but since a good part of it is fairly thin 1/2" ply, actually a tad under I do want to put some framing inside without using up too much inside shelf space. I'm thinking 2x2 framing as well as some for the roof as well. The front obviously will be the weakest link since it'll be a door taking up nearly the entire front wall so I'm thinking I'll need a good sturdy face frame, say nothing about the door itself with a few pieces of 1/4" plexiglass.
The thing bugging me is the joinery to use for the frame.
The right and left walls are actually two pieces each. 1 layer of pieced together 3/4" ply with the 1/2" outer layer. I only did that because I read somewhere that you should at least double up on those walls if possible since it will be outside and exposed to the weather. I dunno..it makes sense to me so those two are about 1 1/4 or a reasonable facsimile.. I'm thinking I should glue em together, but might use screws or both.. I would have liked to have large enough 3/4, but life just doesn't always like me that way..
So..other than the joinery for the corners and such the other thing bugging me is figuring out how to arrange the shelving to accomidate 3 sizes of books, smaller 7" paperbacks, larger 9 1/4" hardbacks and even larger kids books, usually 12" or larger. For now the space I have to work with is roughly 22 1/2" W x 32 H or thereabouts.. I've asked for suggestions from the neighborhood and so far crickets.. Everyone seems to want it built, but not a breathing soul wants to...You know..I really can't repeat my true feelings here on this "family site".. lol It does mention lazy though..and possibly mothers and a reproductive act so I'll leave it at that and let you imagine it..
See what happens when you try to be nice?



I figured it's time to change my signature so hold your breath. This is it.
Impressive, huh?
Marty or Marty Farty if you feel mean.
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post #6 of 6 Old 09-14-2020, 10:46 AM Thread Starter
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Considering using 1" treated deck boards for the framing. Of course I will rip them to the proper width, but they're fairly hard and straight for what I'm going to be using them for, some simple stability and a nailing or screwing surface without using too much of the inside shelf space. I'm thinking that by gluing and tacking two together in an L shape it'll give me a pretty decent inside frame. I only really need four corner posts and a few on the bottom to hold the bottom shelf along with some glue and a dado across the bottom.
Thoughts?
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I figured it's time to change my signature so hold your breath. This is it.
Impressive, huh?
Marty or Marty Farty if you feel mean.
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