# Need ideas to repair water damaged plywood **URL:** \ **Category:** Factual Questions\ **Created:** [June 3, 2018, 3:12pm UTC](https://boards.straightdope.com/t/need-ideas-to-repair-water-damaged-plywood/815358 "2018-06-03T15:12:21Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Tastes\_of\_Chocolate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tastes_of_chocolate/32/3232_2.png) [@Tastes\_of\_Chocolate](https://boards.straightdope.com/u/Tastes_of_Chocolate)\ **Post date:** [June 3, 2018, 3:12pm UTC](https://boards.straightdope.com/t/need-ideas-to-repair-water-damaged-plywood/815358/1 "2018-06-03T15:12:21Z")
I have a hand built camper trailer. It has a body made from plywood with an outer skin of aluminum. As some point, one of the seems had a hole, and rainwater entered, leaving the interior plywood delaminating and with a bit of rot. The area is about 3" square, and while it’s part of the exterior wall (so it’s vertical), it’s not weight bearing. So… Any suggestions on how to patch and reinforce this section of plywood? It needs to be able to deal with bouncing while being towed, be applicable on a vertical surface, and hold together the plywood. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [June 3, 2018, 5:01pm UTC](https://boards.straightdope.com/t/need-ideas-to-repair-water-damaged-plywood/815358/2 "2018-06-03T17:01:11Z")
What’s on the inside? Can you cut an over-sized plywood patch and glue/screw it to the surrounding, undamaged plywood? If you need something thinner, you could use 1/16" steel plate. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [June 3, 2018, 5:11pm UTC](https://boards.straightdope.com/t/need-ideas-to-repair-water-damaged-plywood/815358/3 "2018-06-03T17:11:06Z")
> [@beowulff](#): > > What’s on the inside? > Can you cut an over-sized plywood patch and glue/screw it to the surrounding, undamaged plywood? > If you need something thinner, you could use 1/16" steel plate. Would the rot continue? I think I’d cut it out first. One of those oscillating saws or a very steady hand with and angle grinder would probably do it without cutting the aluminum skin. Cut out out to an easy to replicate shape, then cut a similarly sized plywood patch to set in to the hole. Maybe some glue around all the mating edges (but not from the wood to the aluminum, unless they’re already ‘attached’). From there you could, if you need to, put something over it. Either, like beowulff said, a bigger patch or a strip of something going across it to hold it in. Of course, it’s hard to guess without seeing this. Is replacing the entire sheet of plywood an option? ---
**Author:** ![txjim](https://avatars.discourse-cdn.com/v4/letter/t/f07891/32.png) [@txjim](https://boards.straightdope.com/u/txjim)\ **Post date:** [June 3, 2018, 6:39pm UTC](https://boards.straightdope.com/t/need-ideas-to-repair-water-damaged-plywood/815358/4 "2018-06-03T18:39:32Z")
If you can dry the plywood, a [penetrating epoxy](https://www.jamestowndistributors.com/userportal/product.do?part=440089&engine=adwords&gclid=CjwKCAjwo87YBRBgEiwAI1LkqacrbORuahoKhRgP-996GTCAD-0H2EZcxelfHIFrBOIEQ557eN0IzxoCEfkQAvD_BwE) will work. I use the referenced product for that purpose as well as to seal kayaks I build using cheap plywood. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [June 3, 2018, 8:05pm UTC](https://boards.straightdope.com/t/need-ideas-to-repair-water-damaged-plywood/815358/5 "2018-06-03T20:05:21Z")
> [@txjim](#): > > If you can dry the plywood, a [penetrating epoxy](https://www.jamestowndistributors.com/userportal/product.do?part=440089&engine=adwords&gclid=CjwKCAjwo87YBRBgEiwAI1LkqacrbORuahoKhRgP-996GTCAD-0H2EZcxelfHIFrBOIEQ557eN0IzxoCEfkQAvD_BwE) will work. I use the referenced product for that purpose as well as to seal kayaks I build using cheap plywood. Yes, after cutting out and replacing as much as possible a wood stabilizer can be used. If it’s not a structural issue there are less expensive versions than epoxy like Elmer’s Wood Stabilizer and Minwax Wood Hardener. Any place where the plywood has delaminated should be removed and replaced though. ---
**Author:** ![Tastes\_of\_Chocolate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tastes_of_chocolate/32/3232_2.png) [@Tastes\_of\_Chocolate](https://boards.straightdope.com/u/Tastes_of_Chocolate)\ **Post date:** [June 3, 2018, 8:38pm UTC](https://boards.straightdope.com/t/need-ideas-to-repair-water-damaged-plywood/815358/6 "2018-06-03T20:38:00Z")
Thanks for the ideas. It’s a teardrop trailer, so the whole side is one piece of plywood, with a cutout for a door, and with the aluminum skin. The rot shouldn’t continue. We’re working on fixing the issue that let water in in the first place. This is a test / proof of concept trailer for the builder, and we found a flaw. Replacing the whole sheet isn’t really an option, as that would involve removing and replacing the whole side of the trailer. I’ll be looking into a wood stabilizer, after cleaning up the damaged area. It sounds like I should be looking into wood kayak/boat products. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [June 3, 2018, 9:31pm UTC](https://boards.straightdope.com/t/need-ideas-to-repair-water-damaged-plywood/815358/7 "2018-06-03T21:31:09Z")
You could install a new sheet from inside. 3/8 plywood may be a good choice. Get a good grade. A & B if you can find it. Apply a generous amount of construction adhesive. I Like F-26. Use lots of wood Screws. 3/4 or perhaps 1inch? Make CERTAIN they aren’t too long. You could ruin the exterior siding. The screws will resolve any delamination of the orginal plywood. You’ll have a solid wall. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [June 3, 2018, 9:43pm UTC](https://boards.straightdope.com/t/need-ideas-to-repair-water-damaged-plywood/815358/8 "2018-06-03T21:43:42Z")
3/4" number 8 wood screws are a safe option. Worst case, the original plywood is 1/2". That plus 3/8 is .875. 3/4 (.75) is a safe choice. The wall is probably 3/4" plywood. But there’s no reason to risk 1" screws. Unless you can measure the original plywood. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [June 3, 2018, 10:59pm UTC](https://boards.straightdope.com/t/need-ideas-to-repair-water-damaged-plywood/815358/9 "2018-06-03T22:59:14Z")
> [@Tastes\_of\_Chocolate](#): > > This is a test / proof of concept trailer for the builder, and we found a flaw. You found 2 flaws. The plywood used should have been water-resistant, the exterior grade quality. Trailers are notorious for leaks, especially as they age. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [June 4, 2018, 1:04am UTC](https://boards.straightdope.com/t/need-ideas-to-repair-water-damaged-plywood/815358/10 "2018-06-04T01:04:36Z")
> [@Tastes\_of\_Chocolate](#): > > It sounds like I should be looking into wood kayak/boat products. Look into [Seaboard®](https://www.vycomplastics.com/product-families/seaboard/) ---
**Author:** ![awldune](https://avatars.discourse-cdn.com/v4/letter/a/c77e96/32.png) [@awldune](https://boards.straightdope.com/u/awldune)\ **Post date:** [June 4, 2018, 3:05pm UTC](https://boards.straightdope.com/t/need-ideas-to-repair-water-damaged-plywood/815358/11 "2018-06-04T15:05:03Z")
Why not just use Bondo? (filler putty) ---
**Author:** ![brossa](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/brossa/32/3040_2.png) [@brossa](https://boards.straightdope.com/u/brossa)\ **Post date:** [June 4, 2018, 10:11pm UTC](https://boards.straightdope.com/t/need-ideas-to-repair-water-damaged-plywood/815358/12 "2018-06-04T22:11:34Z")
If the area is only three inches by three inches, why replace it at all? Cosmetic reasons? If the plywood is bonded to the aluminum skin in any way (or even if it isn’t) it might be hard to cut the plywood out without marring the skin - either puncturing it or denting it from the inside. A trim router would let you control the depth of cut precisely, and if you rout with a guide bushing around a template you can make a patch the exact same size and shape as the hole. If the plywood surface is curved, this will be much more difficult since it’s hard to force a small piece of plywood to follow a curve. In that event you might need to use a solid wood patch and plane or sand it to fair up the curve. Perhaps you can cut all the way through the wall at this spot and make it an air vent or window?