lumber waterproofing

[mrsclem]

We have finally gotten our rebuild done on our old pond. We put the new frame inside the old so have a double wall pond and cannot use the 5" Trex boards for the edging. I have 2x8s that are not treated and I seem to remember someone using marine sealant for waterproofing. I cannot find the post so checking to see if anyone can make a recomendation as what I should use to treat the cap boards that would be safe for the fish. Thanks-

 

[sissy]

you can also buy the new pressure treated wood it is treated in a new way that is done with 100% safe products they even say you can eat it .Trex boards can be used even thought they are not wide enough they can be joined together .

 

[mrsclem]

What the stores carry here still has warning labels on it. I got untreated 2x8s but not sure if something like Thompsons water seal is safe or not.

 

[Waterbug]

Safe is a relative term, but I'd consider Thompsons water seal safe. Pretty inert when dry. Resealing it every year could be an issue, hard to keep from dripping into the pond. A few drops probably won't hurt anyone, knocking the whole can in probably wouldn't be good..

I had 2x6 caps on a few ponds and used oil based stain. On the plus side when I dripped the stain floated and could be soaked up with a paper towel if I was quick. These days I'm more into making sure wood is easy to removed for maintenance. Safer and easier.

 

[mrsclem]

Thanks Waterbug- I sent Thompsons an email and asked about the safety but haven't heard back. Going to use deck screws to put the wood on so will be able to remove easily.

 

[sissy]

thats a shame as lowes and home depot have alot of the new stuff here and have big signs over it .They say it is thermo treated on all the signs and the price is close to the same as regular treated lumber .

 

[mrsclem]

Thanks to everybody for the replies. Decided to play it safe and just put the boards up untreated and then remembered I still had some rock on a roll left over. Stapled it to the 2x8s and used PL roof cement to anchor it to the liner. Need to order more but it looks a whole lot better than just the liner showing.
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[frito]

Mrsclem, I need to build a double wall pond like yours, but on a concrete surface. Could you tell me how you did this, and what supplies you used for the frame? And is the sand in between the walls "necessary" ?

 

[Waterbug]

Frito, here's a couple examples of raised ponds I built on a concrete slab if you're interested.

Here's a link to the page with a description. The Upper pond was built the same way only larger.

I disassembled these ponds after about 5 years and there was a fair amount of rot on the plywood. For smaller ponds the lumber was fine, but that Upper pond was 16' long, 3' high and did bow out at the top. On the top course I had to lay the 4x6 on its side to stiffen it.

When I started I assumed building with wood would be faster and easier, it wasn't. Dry stacked concrete block filled with rebar and concrete cost about the same, about the same effort, a little more flexible in the design, longer lasting and stronger.