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What would you guys suggest to completely seal wood (probably plywood) from moisture. I'm building a new tank/vivarium for my lizard and while it is not going to be as damp as something like a frog tank, I still want it to be 100% sealed so I never have to worry about it (even if the inhabitants change down the road to something that needs to have rain-showers several times a day).

I've heard from reptile groups that people have used Pond Sealer, some people advise Drylock...

You are wood-working people though so I was hoping to get a more consistent answer here: What will leave the wood 100% moisture-proof, be completely vapour-free when cured (ie. safe for the inhabitant), and as a bonus: resist being scratched by smallish-reptile-claws (she digs at the walls in her tank occasionally).

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  • Search for plywood aquariums -- anything that can be used to build a 1500 gallon aquarium would be sufficient (if possibly an overkill) for a vivarium. Here is a guy sealing fairly big one with paint epoxy: youtube.com/watch?v=dS6AJL3CAt0&t=0s
    – Eugene
    Commented Sep 26, 2016 at 17:14
  • Whatever sealant you choose, consider using marine plywood.
    – James Youngman
    Commented Oct 1, 2016 at 8:25

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I'll preface this by saying that this may be a question that would be better asked on a forum of like-minded animal owners, some of whom will have tackled similar builds and they'll be able to report what worked and what didn't.

It is very difficult to seal wood off completely from moisture using common coatings and finishes. Most of the time when woodworkers say "seal the wood" they're speaking informally...... very informally, because most coatings only do a partial job of isolating the wood from its environment and some do almost nothing!

Products that will 100% waterproof wood include bartop finishes, marine epoxy coatings and fibreglass resin, but in addition to their waterproof nature for a complete seal it also requires them to be put on thickly, the equivalent of perhaps 20 coats of regular varnish, so there is a very significant coating on the surface.

The good news is I don't think you need to go that far. Because many similar habitats I've seen, built mostly from plywood, seem to be finished off in basic coatings (probably varnish, based on the appearance and guesswork) and not in something visibly thick and with a slick, high-gloss finish.

My suspicion is that if you use a decently water-resistant material (e.g. a suitable grade of plywood and/or any solid wood that naturally does well outdoors) and simply varnished it thoroughly that you'd get the performance you want. For this I'd use polyurethane* which has good scratch-resistance. Apply four full-strength coats minimum, but six or seven would be better. If you wipe the varnish on to make it easier to apply (see wiping varnish) you'll want to use at least 7-9 coats for an equivalent to four unthinned coats applied by brush.

*I mean oil-based poly here and not the waterbased type which is a completely different thing.

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    Every time I try to find an answer on a reptile group it becomes a virtual fist fight with no useful info presented. Last time it was Pond Sealer VS Drylock.
    – BunnyKnitter
    Commented Aug 9, 2016 at 17:00
  • @SnyperBunny, oh, that's a pain, and just like woodworkers when it comes to sharpening threads then! Can any useful info be gleaned from such a slugfest though — how Drylock holds up over time when applied to wood, whether reptiles don't mind the smell, anything like that?
    – Graphus
    Commented Aug 10, 2016 at 7:06
  • Last time one side of it went "pond sealer rox, you all suck for not thinking so too!! I'm leaving the group!" :(
    – BunnyKnitter
    Commented Aug 10, 2016 at 15:10
  • @SnyperBunny, LOL, oh that well? It may still be possible to draw some useful conclusions from that sort of thread as there might be another parallel with sharpening threads. One of the reasons you get people defending the system they use so passionately is they all work and it's that point that gets lost in the noise. So it's possible that all of the options that people argue about on reptile-fancier forums might be workable solutions, just pick one and go for it.
    – Graphus
    Commented Aug 11, 2016 at 7:18
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I think your best bet would be epoxy. Although it is a pain to apply on large surfaces, it will address all your concerns.

  • It's 100% moisture proof (or as close as you can get),
  • quite scratch resistant as it is very hard when cured,
  • vapor free when cured (at least to the best of my knowledge, I researched this quite a lot a year or so ago and opinions vary on this point)

When working with epoxy I'd read up a bit on the topic though and watch a few tutorials and make a test piece at first. This stuff has a nasty smell while working it and there are more than a few health and safety concerns when handling epoxy one should be aware of.

One thing that might not be evident in most tutorials/guides: As you want this in a vivarium i guess there will be a heat-lamp. One aspect of the epoxy is that it will start to cure further when heat is applied.

Meaning that if you let the epoxy cure at ~20°C (68°F) and then put it in the vivarium where right under the lamp you have temperatures exceeding 35°C (95°F) the chemical process will pick up once again and there will be vapors. That means you might want to cure the epoxy at a temperature exceeding the final temperature of your vivarium. This will make it even harder, but take even more time to cure (up to several days).

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  • As @Graphus' answers are usually spot on and he's got way more experience than me (judging from the quality of his posts) I'd go with his answer. Maybe mine will be some food for thoughts though :)
    – Stoppal
    Commented Aug 9, 2016 at 8:24
  • Thank you - what would you suggest I look for in an epoxy? Are there any good quality-cheap brands you would recommend? Also, thanks for mentioning the heat!!! That could have been bad. I'll have to drag her heat lamps outside on a dry day and blast the empty box.
    – BunnyKnitter
    Commented Aug 9, 2016 at 17:18
  • There are epoxies intended specifically as coatings for bar tops and the like. One of them might be suitable. I'd worry a bit about exposing the beastie to those chemicals, though; there are reasons terrariums tend to be metal and glass. Maybe a 16th-inch metal sheet over the plywood?
    – keshlam
    Commented Aug 9, 2016 at 18:59
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    @SnyperBunny While it's expensive, power wise, you could also go with a hairdryer mounted about 0.5 m (~2 ft) from the surface. As for the brand and kind of epoxy, the stuff I use is this one. The 'famous' youtube woodworkers use mostly the "West System" stuff from what I've seen. I think it's more a question of availability and application. In your case I'd use slowly curing stuff as it's said to cure more evenly (emphasis on the "it's said" part).
    – Stoppal
    Commented Aug 9, 2016 at 19:30
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    @SnyperBunny I just read the (German) reviews on the amazon link again and someone already did exactly what you are planning to do with great success. :) Thought that worth mentioning.
    – Stoppal
    Commented Aug 9, 2016 at 19:44
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It may be a little expensive depending on how much you need, but the phenolic-impregnated WebbWood materials (webbwood.com) may work for you. When it is being made, all the moisture is removed using a heat and vacuum process, then phenolic resin is introduced & is pulled in to replace the moisture. We put a piece of WebbWood PH material in a water bath for six months, then weighed it to see how much water had been absorbed - as far as we could measure, there was zero absorption.

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