Results 1 to 8 of 8

Thread: Edge Sealing Plywood in Non-Marine Appication

  1. #1
    Join Date
    Jun 2006
    Location
    Blacksburg, VA
    Posts
    471

    Default Edge Sealing Plywood in Non-Marine Appication

    Not a marine application, but I thought some in the forum might have useful input.

    I'm building a firewood storage box for outdoor use. Most of the box is built from yellow pine, but the lid is exterior BC yellow pine plywood. Nothing fancy - all the lumber is left over from other projects. The box will be partially sheltered by a roof overhang, but will still get wet in a hard rain. The lid is about 20x35 inches, hinged on the long edge. The lid is pitched so that water will run off.

    I plan to finish the box with a penetrating oil, but I'm not sure whether that will work for the lid. I'm afraid that even with the oil finish, water will get into the edges of the plywood and cause delamination. Another option for the lid is to seal the plywood edges with epoxy and then paint the lid. I figure that once I've sealed the edges (and necessarily dripped some epoxy on to the flats) I''ll never get an even finish with the penetrating oil, and the epoxy will need protection from UV. A third option is to install edge banding on the plywood with epoxy or Titebond 3 and then finish with either oil or paint.

    I would prefer to just go with the oil finish. I would never try that on a boat, but I thought it might be OK for ordinary exterior use. Does anyone out there have experience with plywood edge delamination in ordinary exterior use?
    I will beg you for advice, your reply will be concise, and I will listen very nicely and then go out and do exactly what I want! (Apologies to Lerner and Lowe.)

  2. #2
    Join Date
    Oct 2000
    Location
    Padanaram, MA USA
    Posts
    9,865

    Default Re: Edge Sealing Plywood in Non-Marine Appication

    If itís fir plywood, no finish will last long. Iíd sheathe with light (6 oz.) glass wrapped around the edges. THen paint.

    If itís MDO, coat the edges with epoxy and paint it.

  3. #3
    Join Date
    Jun 2006
    Location
    Blacksburg, VA
    Posts
    471

    Default Re: Edge Sealing Plywood in Non-Marine Appication

    Quote Originally Posted by JimConlin View Post
    If it’s fir plywood, no finish will last long.
    It's SYP plywood. I know that it will check if painted or finished with a bright, hard, finish. I was thinking that a penetrating oil that doesn't form a hard finish would move with the wood and not check. My concern is with delamination from water entering the edges.
    I will beg you for advice, your reply will be concise, and I will listen very nicely and then go out and do exactly what I want! (Apologies to Lerner and Lowe.)

  4. #4
    Join Date
    Jun 2000
    Location
    Pleasant Valley NS Canada
    Posts
    20,761

    Default Re: Edge Sealing Plywood in Non-Marine Appication

    Apply a barrier tape on the topside to within 1/2" of the edges, Paint the edges with epoxy, then a primer and finally exterior-grade paint - dark green would be nice. Remove the tape and oil the panel.
    Hope for the best, but plan for the worst.

  5. #5
    Join Date
    Jan 2011
    Location
    Norwalk CT
    Posts
    1,506

    Default Re: Edge Sealing Plywood in Non-Marine Appication

    Frankly no matter what you do other than glass the whole thing, the plywood is gonna check and warp and generally be a PIA. Why not just make a wood top?

  6. #6
    Join Date
    Oct 2009
    Location
    Newport, OR
    Posts
    429

    Default Re: Edge Sealing Plywood in Non-Marine Appication

    Best luck so far has been with Smith's or a similar penetrating epoxy. But without glassing the big horizontal weather surface you'll still end up with water in the plywood.
    1973 Grand Banks 42

  7. #7
    Join Date
    Mar 2009
    Location
    Texas
    Posts
    5,406

    Default Re: Edge Sealing Plywood in Non-Marine Appication

    I just finished a similar hatch. I put flashing around the edges, tar paper, then corrugated metal. All leftover. For a small hatch, it doesn’t take much. Will last forever. And the light stuff is cheap or free if you use leftover.
    Last edited by bluedog225; 08-02-2020 at 12:15 PM.

  8. #8
    Join Date
    Dec 2003
    Location
    Portland, Oregon
    Posts
    66,650

    Default Re: Edge Sealing Plywood in Non-Marine Appication

    Quote Originally Posted by bluedog225 View Post
    I just finished a similar hatch. I put flashing around the edges, tarp paper, then corrugated metal. All leftover. For a small hatch, it doesn’t take much. Will last forever. And the light stuff is cheap or free if you use leftover.
    Not everyone lives in Texas.

    alkorn - you're right to pay particular attention to the edges. And you're right that oil over epoxy is pointless. That epoxy is the best seal for the edges, but needs to be protected from UV degradation. I like the notion of oiling the field after epoxying and painting the edges. I like even better: glass+epoxy the entire plywood top, then paint. More work, but will be hold up best and be easiest to clean off quickly. Between one of those approaches, and the slope, you should be fine for a long time.
    David G
    Harbor Woodworks
    https://www.facebook.com/HarborWoodworks/

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  9. #9
    Join Date
    Nov 2008
    Location
    tacoma washington
    Posts
    1,209

    Default Re: Edge Sealing Plywood in Non-Marine Appication

    tar paper and shingle, with flashing on edges.. a 2by for underside bracing the plywood lid. a block of wood to hold the lid open during the summer months/ or when freshly cut..in short, treat just as you would if you were building a house

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •