I am building a horizantal slat fence with 1x4 lumber. None of the lumber I look at is straight enough or too expensive for fencing. I am wondering if I slice up 3/4" exterior plywood and paint it how it might hold up over several years. I live in So cal on the coast. Cool Damp mornings and evenings but not much rain.
Should do really well if you carefully seal the edges with primer and then a coat of paint. I’d recommend spending a little extra for marine grade plywood. You could belt sand the plywood with some medium grit before cutting it up into strips. Gives a smoother finish for the paint.
You’ll probably find a few voids in the plywood. That’s normal. Small pockets where a knot hole used to be. Look for those along the edges of the strips that you cut. They might hold water and rot the wood. So, install that strip with the defective edge facing down.
If you do belt sand, use a 100 grit. Keep the belt sander moving. It can eat through the plywood veneer pretty quick.
Exterior grade plywood is a lot rougher than interior grade. It does need some sanding for a nice paint finish. Not a lot. A few minutes with 100 grit is all it takes for a good paint finish.
Decent marine ply shouldn’t have voids - but then, it costs more.
If you paint with a couple of coats of thinned primer, it will soak in better to the veneers and this should provide even greater protection.
I’ve picked up pieces of marine ply driftwood where the edges were all worn to round, but it still wasn’t delaminating - must have been in the water for ages - so I’d imagine it would last a few years as a fence, even in an exposed situation.
Good info, I have a good plywood blade, I wonder if my planer would smooth it better than the sander just running very thin cut on one side only.
The planer will tend to tear alternate veneers within the ply, because you’re cutting across endgrain - possible to get away with this if the blade it very sharp and the speed is very high, but it’s risky.
If you have a high speed router and a decent cutter, you can get a nice smooth edge on ply with that - clamp a batten onto the plank to act as a fence - positioned so that when you run the router shoe along it, the cutter just grazes the edge of the ply.
plywood edges need to be sealed well.
for decorative uses you might also look at manufactured lumber, it costs more but is low maintenance and long lasting. it is made from recycled plastic and waste wood.
I have a special german tablesaw blade that gives me a flawless but sharp edge which would be ok for a fence. I will use my 6" sander and just set it up like a thickness sander. Fence is not that big 22’X6’ high, maybe about 4 sheets of ply cut up,
It might work if the fence boards are off the ground. Even then it’s not likely to last as long as plain wood. If you want a fence to last, use cedar. It shouldn’t be that expensive if you shop around. And don’t paint it, that just helps moisture stay in the wood leading to rot. Even plain pine will last a long time if there’s plenty of air circulation around the wood.
I also would recommend cedar rather than cutting slats out of marine plywood. It may even be cheaper.
You can oil the cedar every year or so and it will last a long time. Marine plywood is not meant to be cut into thin slats like you need for a fence and will probably deteriorate fairly fast. And MP it is pretty expensive.
My son nixed the plywood anyway so cedar it is. Most of the Home depot and Lowes cedar I looked at was terrible. I will check out the better lumber yards. He specified clear cedar.