This will take a little explanation. At the non-profit group where I work, we moved last summer into an open office space where we had to build our own walls, shelves, etc.. Since we’re a design outfit, the construction was “different” from the norm. On the last partition wall there was a lot of varying thicknesses of plywood left over so I cut the pieces into various rectangular strips and attached them to a stud frame in various 90 degree configurations. Mostly horizontals, but some verticals and overlapping pieces. It actually worked really well (you can see thru the gaps, but there aren’t any secrets here), and I wanted to do something similar for a fence I’m building at home. The problem is . . .
water. Obviously, the elements would turn regular plywood into toilet paper over enough time, but what about marine plywood? Will probably only have time to do the dog’s area (and hopefully remove the existing fence and set the rest of the posts before winter . . . this is a weekend thing), so that will probably be my “test area.” I know marine ply will resist rotting, but I’m concerned about the edges. Does anybody have any experience with the stuff, and has anybody seen it fray/delaminate/swell from water penetrating at the cut sides? And, yes, I know there are other fences that will cost a ton less, be considerably easier to put up, and will probably make more sense in the long run . . . but that would be the intelligent thing to do (and I’m not about to be accused of being smart).
As usual, any help/comments much appreciated.
Replies
The problem is keeping water out of the edges where it can get at the glue. You might try the paint-on roofing material from RCT:
http://www.conservationtechnology.com
-- J.S.
The primary aspect of marine plywood is, when the veneers are layed up, extra care is taken to keep the veneer plies edge to edge and eliminate voids as are found in most construction plywood.
Other than that, it isn't anymore "waterproof" than any other plywood and is quite expensive.
You might consider looking for pressure treated plywood; the treatment plants near me use AC grade and we use it for dock ramps and other exposed applications and, here on the coast, I often sheath the first 2 feet of exterior walls with it if they are going to be subject to frequent dampness by close placement of landscape plants.
The PT stuff has proven to hold up for a long time (like 15+ years), even with exposed edges, in the weather, with no delamination.
And when it's dried out, it can be painted.
My only experience is with Doug Fir PT plywood....can't speak to others.
Notchman
your in Oregon I think, but Oregon is big served by many vendors
for us ( also in Oregon) if we say Marine, it is automatically Pressure treated
I also agrew with your technique even though we are valley folks
if its a high water area, we use marine (p.t.) plywood too, why not
its piece of mind at night and piece of mind for a honest builder is priceless
No, Marine is NOT pressure treated.....I've built a bunch of boats over the years....good USA made marine plywood is hard to come by; the good stuff, the real serious stuff, comes from places like Norway and Finland.
Years ago, I worked in a local plywood mill for a while and they layed up a lot of marine playwood for some Navy order....it was nice stuff....clear faces and cores...I don't recall the # of plies or the thickness, but it was probably at least 7 ply, maybe 9.
Some of the European stuff is the metric equivalent of 1/4" and may have 13 or 15 plies.
(Decent plywood, even CDX, will always have an odd # of plies)
ok
Im a fool
when I ask my local lumber yard for marine grade, it is pressure treated
maybe its just me and my connection and buddy in contractor sales
I stand corrected
I'm not picking on you....no need for contriteness; it's Friday nite!
Where are you, Portland area maybe? With all those floating houses on the Columbia, they need all the PT they can get....marine or otherwise!
Notchman, thanks for the advice on PT plywood. Will go with that (sorry about the late reply, I didn't get back to the computer until Monday).
Is that PT the new corrosive stuff? What nails do you use?
-- J.S.
I've been using galvanized ringshanks as always....I keep the better part of a unit quantity (1/2" and 3/4") in the loft of my barn, so it's pretty dry by the time I use it.
The new PT hasn't seemed to have any affect on the nails (thus far).
Notch - My experience with PT plywood was horrible. I had a trailer bed redone in 3/4 plywood. Within 2 years, it's so weak and flexible, you take your life in your hands walking across it. I originally asked for marine ply, was told this was just as good. Next time, I get the marine stuff. Don
Maybe it's a regional thing; I dunno. But we use a lot of it here on the Oregon coast; for ramps, docks and sheathing as I've described....no problems with it.
It's all Doug fir, AC grade usually, and there are two treatment plants locally.
Notchman - I could have gotten a bad sheet. Maybe it was something other than what you are talking about. (I didn't actually go to the store and pick it out.) I know it was the PT Green plywood. I know what happened to it too quickly thereafter.
For what it's worth, a good friend of mine paid for PT 6x6's for a retaining wall a few years ago. 30 year warranty, or some such. 5 years later, a third of them are mush. Go figure...I'm not a believer.
Don
What about MDO?
-Jazzdogg-
"Don't ask yourself what the world needs. Ask yourself what makes you come alive, and go do that, because what the world needs is people who have come alive." Gil Bailie