Drylock is designed as a concrete sealer… I’ve used it in the repair of a leaking basement wall… I’ve also used it to water proof a retaining wall…
　
I have used it to seal a 4’ x 2’ x 2’ lizard cage. The cage was designed built to be water tight as I pour water directly onto the mulch quite commonly. At two years old the cage is still 100% leak proof (cleaned and leak tested in January).
　
I’ve also used Drylock on several terrariums to make Styrofoam look like rock…
　
I know a local guy who built a couple hundred gallon Drylock/plywood tank and it lasted 4~5 years then the Drylock started peeling/flaking…
　
I have a friend via forums who built a 2,000’ish gallon plywood tank and lined it with Hariboard (basically concrete plywood) and painted the Hardiboard with Drylock. The tank has not leaked… he said if he could do it over again he would do it without the Hardiboard as he believes the Drylock on Ply would be fine…
　
　
With my experience of using it on both brick/block, plywood and lumber…Drylock will bite into and hold onto a rough surface better than a smooth surface… Put on a very thin first coat and allow successive coats get slightly thicker… If the box is very solidly built so that the wood has absolute minimal flex, the Drylock alone should work well. If you fear your corners flexing and cracking then overlaying the corners with silicone may protect cracks from leaking… If the flat open areas of Plywood flex as the tank is filled and drained, this will promote flaking/peeling. Thus I suggest solid framing…
　
　
Resealing Drylock was mentioned previously… it is very true that cracks in the Drylock can be overcoated with Drylock or one of several other products… but if the Drylock flakes or peels, overlaying it will not repair it. As the problem is at the Ply/Drylock interface not the drylock/air interface.
　
　
I am building a larger lizard cage now… and I am simply painting the plywood inside of it’s water area (2.5’ x 1’ @ 1’ deep)… I fully trust this will hold water long term without concern of leaking…
　
If I built a large indoor tank to be filled with water, I would be hesitant to trust Drylock on Ply long term… I would likely use Hardiboard… But there is a very good chance that with solidly framed walls that prevented flex it would work fine without hardi…
　
For an outdoor box that I was hoping to get a 4~5 year lifespan out of… I’d build the box as solid as practical and Drylock the Ply…
　
I have used it to seal a 4’ x 2’ x 2’ lizard cage. The cage was designed built to be water tight as I pour water directly onto the mulch quite commonly. At two years old the cage is still 100% leak proof (cleaned and leak tested in January).
　
I’ve also used Drylock on several terrariums to make Styrofoam look like rock…
　
I know a local guy who built a couple hundred gallon Drylock/plywood tank and it lasted 4~5 years then the Drylock started peeling/flaking…
　
I have a friend via forums who built a 2,000’ish gallon plywood tank and lined it with Hariboard (basically concrete plywood) and painted the Hardiboard with Drylock. The tank has not leaked… he said if he could do it over again he would do it without the Hardiboard as he believes the Drylock on Ply would be fine…
　
　
With my experience of using it on both brick/block, plywood and lumber…Drylock will bite into and hold onto a rough surface better than a smooth surface… Put on a very thin first coat and allow successive coats get slightly thicker… If the box is very solidly built so that the wood has absolute minimal flex, the Drylock alone should work well. If you fear your corners flexing and cracking then overlaying the corners with silicone may protect cracks from leaking… If the flat open areas of Plywood flex as the tank is filled and drained, this will promote flaking/peeling. Thus I suggest solid framing…
　
　
Resealing Drylock was mentioned previously… it is very true that cracks in the Drylock can be overcoated with Drylock or one of several other products… but if the Drylock flakes or peels, overlaying it will not repair it. As the problem is at the Ply/Drylock interface not the drylock/air interface.
　
　
I am building a larger lizard cage now… and I am simply painting the plywood inside of it’s water area (2.5’ x 1’ @ 1’ deep)… I fully trust this will hold water long term without concern of leaking…
　
If I built a large indoor tank to be filled with water, I would be hesitant to trust Drylock on Ply long term… I would likely use Hardiboard… But there is a very good chance that with solidly framed walls that prevented flex it would work fine without hardi…
　
For an outdoor box that I was hoping to get a 4~5 year lifespan out of… I’d build the box as solid as practical and Drylock the Ply…
