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billymcgarry 10-25-2012 09:55 PM

exterior plywood Marine
I am covering an exterior building with marine plywood and want to make the seams disappear. What can I use to tape the joints

joecaption 10-26-2012 09:28 AM

#1 Why the maraine grade, unless your getting it for free it's one very expencive way to go with nothing to gain.
There is no magic tape to cover the seams.
Is it at least Tonged and groved or have an over lap to air seal it?

Gissle 10-27-2012 06:18 AM

Yes, you should use timber cladding, which will have grooved joints.

user1007 10-27-2012 09:55 AM

Why not some nice redwood or cedar siding for just such purposes? I assume the building is structurally sound and you are just using the plywood as a veneer?

woodworkbykirk 10-27-2012 10:55 AM

the only reason i can see using marine grade is if your directly on the water. salt water specifically. if your worried about rot from excess moisture id use the wood framing blueskin if your going over it. i believe its blueskin xp or something, it still breathes so you dont get dryrot

notmrjohn 10-27-2012 11:17 AM

Why are you using marine grade?
Caulk the seams, if tongue and groove fill groove with caulk slide together make sure its firmly seated, squeezing out most of caulk. If not T&G caulk seams, cover with a batten. A 1X2, 1X3 or 1X4 over the seam. You can cover T&G with batten if you want. I assume you are using marine grade for a durability purpose? Best use pressure treated, cedar, or redwood for battens.

Major difference between marine and exterior grades is surface appearance and size and number of gaps or voids in interior plys. The glues are usually identical.

Above marine grade are sign board grades. No voids allowed, no knots, sanded extra smooth, superior resin glues. Stuff lasts forever, it ought to considering price and you have to get it from sign makers supply.

notmrjohn 10-27-2012 11:39 AM

I'm back already. "seams disappear", you want the seams to be non-visible rather than seal them? Treat it as if it were dry wall only using fiber-glass strips instead of tape and mud. You'll have to sand a taper along the edges of plywood just as drywall has. Then embed "tape" in resin. Plywood will expand and contract some, final resin gel coat may crack. Might need a deeper wider taper, narrow strip of glass with two or more strips over it, each wider than one below. Go as wide as you can, as many layers as you can,without building up a bulge or having edge of tape over untapered plywood. Feather out edges of each coat of resin. Feather sand final edges of resin and tape, a final coat of bondo or other body filler feathered out. It would probably bee good idea to oils base prime and paint all surfaces and edges of ply before fiber glass, to reduce expansion and contraction, Then lightly sand areas to be fiber glassed.

Gary in WA 10-27-2012 09:45 PM

Not as siding;

Leave the joints open for expansion to prevent buckling;

PS. welcome to the forums!

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