Waterproofing concrete pond: plaster, fiberglass, painted-on rubber?

[moocowman]

I'm building 3 foot wide x 20 foot long x 30 inch deep rectanglar in-ground concrete pond. I've already plumbed and I'm just starting to install rebar. I can't decide on a method of waterproofing the pond. It's being built like a swimming pool. So I was thinking of plastering it like they would a pool. I've watched several videos of people using fiberglass to waterproof (seems like mostly in the UK). I've done a lot of fiberglassing before. I'd probably use epoxy resin instead of polyester resin. I'm torn on any products that are paint brush or roller applied. I see a lot of good reviews, but also a lot of bad ones reporting failures. It seems like the film thickness isn't enough to be durable. I don't want to use a rubber liner because I can't hide the edges of the liner and I seems sealing around fittings like the returns, main drain and skimmer would be difficult since all the parts are made for concrete pools.

Would someone with professional experience or someone who has had a waterproofing method hold up for decades chime in with some advice?

 

[Lisak1]

Welcome @moocowman !

Not a lot of folks with concrete ponds here - most are EPDM lined ponds - but hopefully someone will chime in with a helpful answer.

@GBBUDD - any help here?

 

[j.w]

@moocowman
Me too, no experience w/concrete, sorry.

 

[GBBUDD]

There are companies that can make you any size box shape you want that has welded seams. They will never fail I believe they are pvc base product. Not to be confused with cheap pvc sheeting. It is a flexible material similar to EPDM.
The key to any of the other applied coatings is the concrete it's self . The preparation timing and application method is critical. Some demand the concrete still be green so the coating can blend with the concrete . While others demand the concrete be clean ,dry and solid.
I have seen where a spray on liner like rhino liner truck bed liner spray has been used. I know I bought a cheap brand years ago that came with a gun that let's just say didn't even try to eliminate orange peel texture. But I can assure you it was water tight. Can I say it was fish friendly no . But I doubt it wouldn't be toxic as most of those are a urethane base and those to my knowledge are fish friendly.

And like you mentioned there is plaster nothing wrong with plaster in any way when applied properly can give you 20 years with no issues. But eventually will start to alagator Crack. But this is a proven product as swimming pools are still using plaster to this day.

I will add that generally the higher the psi of concrete the more water resistant that it generally is. For my money plaster and some die would be my choice white however would not be my first choice as it will show the algae and the greens and brown that just look dirty.

 

[Laaf]

My concrete ponds are just concrete. No waterproofing was applied.

 

[GBBUDD]

You can get specific mixes that are waterproof but they can get pricey. 5000 psi is close add fiber and additive and you got some strong stuff.

 

[zeuspaul]

I used Rapid Set mortar mix available at Home Depot and Lowes to seal my concrete block pool. I troweled it on. It is stronger than portland cement products and doesn't shrink. Over ten years and still holding water. I did not want to use epoxies or paint because of the difficulty of getting something to stick years later if it needed repairs.

 

[PNDFARY]

I used Rapid Set mortar mix available at Home Depot and Lowes to seal my concrete block pool. I troweled it on. It is stronger than portland cement products and doesn't shrink. Over ten years and still holding water. I did not want to use epoxies or paint because of the difficulty of getting something to stick years later if it needed repairs.

You did this about a year ago? How is it holding up? I’m in the final stages of installing my concrete pond and am looking for water proofing material. Did you put the RapidSet over concrete like pool plaster? Can it be tinted? Or, does it set medium-dark gray?

 

[zeuspaul]

I built the pool in 2006 and it is still holding up. I haven't had to make additional coats. If needed all I would have to do would be to clean the surface. I don't know anything about applying pool plaster. Isn't it sprayed on?

I applied it over raw clean block with a 4 inch trowel that would be used to work with dry wall. The native color is a light brown. It can be tinted with colors available for tinting portland cement products. It has a short working life, maybe about twenty ? minutes.

 

[PNDFARY]

From what I recall from 45 years ago when my folks had a pool put in, gunite is sprayed in and plaster is applied by hand. I’m just trying to figure out what formulation to use for a pond. New to concrete, I’ve been using pond liners forever, I want to be sure this one is watertight and safe for my fish. I thought something in cement is toxic, I have read that concrete leaches something into the water and/or the water seeps out. Ugh! Research is confusing me more.
Thanks for responding. Here is what I have so far. One more coat of concrete on the bottom, then … ? I was going to run a thin coat over the blocks, but it seems like you didn’t.

I’d like to get this half of the pond finished so that I can return the fish to their home. Then I’ll finish the left half.

 

[moocowman]

I ended up making my own pool plaster. Turns out pool plaster is simply 1 part cement and 2 parts sand. I was really skeptical about the mix and application. The materials sounded too simple and I thought it was weird you're supposed to fill with water within 24 hours of applying the plaster. But it worked exactly as it was supposed to. I finished the pond a year ago. It turned out as well as I had hoped.

There's a lot of confusion on pool materials, I think some intentional to protect the industry. In California, I couldn't find anyone to sell me "pool plaster" unless I had a contractor's license. I read several places that pool plaster is simply 1 part cement and 2 parts fine aggregate, like sand. The cement doesn't have to be anything special, simple portland cement will do. The sand doesn't have to be anything fancy, like marble sand, quartz, etc. Pretty much any sand will do. I used "construction sand", also known as "silica sand" dirt cheap from Home Depot. If you want a certain color, you can use white portland cement and mix in pigments. You can also use different aggregates for different colors or effects.

Another misconception is plaster seals the concrete. Water soaks right through plaster. Plaster is purely decorative and provides a smooth surface to hide the rough concrete underneath. I watched a lot of videos with pool contractors who falsely or erroneously think plaster seals water. In fact, you don't have to plaster concrete at all if you don't care what the surface looks like.

There's a lot of confusion on concrete as well. A lot of people think Gunite or Shotcrete refers to the plaster. It doesn't. They're just trade names for spray application of concrete. Whether you pour concrete or you apply Gunite or Shotcrete, you end up with the same thing, a concrete shell. Gunite or Shotcrete are no stronger than poured concrete unless you use a weak concrete mix.

I built the pond like you would a swimming pool. I used swimming pool parts, instead of pond parts, like the main drain, skimmer and auto-fill. When I compared parts, I found pool parts to be a lot more durable, while surprisingly lower cost. Also, replacement parts are easier to find than pond parts.

 

[moocowman]

I ended up making my own pool plaster. Turns out pool plaster is simply 1 part cement and 2 parts sand. I was really skeptical about the mix and application. The materials sounded too simple and I thought it was weird you're supposed to fill with water within 24 hours of applying the plaster. But it worked exactly as it was supposed to. I finished the pond a year ago. It turned out as well as I had hoped.

There's a lot of confusion on pool materials, I think some intentional to protect the industry. In California, I couldn't find anyone to sell me "pool plaster" unless I had a contractor's license. I read several places that pool plaster is simply 1 part cement and 2 parts fine aggregate, like sand. The cement doesn't have to be anything special, simple portland cement will do. The sand doesn't have to be anything fancy, like marble sand, quartz, etc. Pretty much any sand will do. I used "construction sand", also known as "silica sand" dirt cheap from Home Depot. If you want a certain color, you can use white portland cement and mix in pigments. You can also use different aggregates for different colors or effects.

Another misconception is plaster seals the concrete. Water soaks right through plaster. Plaster is purely decorative and provides a smooth surface to hide the rough concrete underneath. I watched a lot of videos with pool contractors who falsely or erroneously think plaster seals water. In fact, you don't have to plaster concrete at all if you don't care what the surface looks like.

There's a lot of confusion on concrete as well. A lot of people think Gunite or Shotcrete refers to the plaster. It doesn't. They're just trade names for spray application of concrete. Whether you pour concrete or you apply Gunite or Shotcrete, you end up with the same thing, a concrete shell. Gunite or Shotcrete are no stronger than poured concrete unless you use a weak concrete mix.

I built the pond like you would a swimming pool. I used swimming pool parts, instead of pond parts, like the main drain, skimmer and auto-fill. When I compared parts, I found pool parts to be a lot more durable, while surprisingly lower cost. Also, replacement parts are easier to find than pond parts.

 

[moocowman]

 

[PNDFARY]

I ended up making my own pool plaster. Turns out pool plaster is simply 1 part cement and 2 parts sand. I was really skeptical about the mix and application. The materials sounded too simple and I thought it was weird you're supposed to fill with water within 24 hours of applying the plaster. But it worked exactly as it was supposed to. I finished the pond a year ago. It turned out as well as I had hoped.

There's a lot of confusion on pool materials, I think some intentional to protect the industry. In California, I couldn't find anyone to sell me "pool plaster" unless I had a contractor's license. I read several places that pool plaster is simply 1 part cement and 2 parts fine aggregate, like sand. The cement doesn't have to be anything special, simple portland cement will do. The sand doesn't have to be anything fancy, like marble sand, quartz, etc. Pretty much any sand will do. I used "construction sand", also known as "silica sand" dirt cheap from Home Depot. If you want a certain color, you can use white portland cement and mix in pigments. You can also use different aggregates for different colors or effects.

Another misconception is plaster seals the concrete. Water soaks right through plaster. Plaster is purely decorative and provides a smooth surface to hide the rough concrete underneath. I watched a lot of videos with pool contractors who falsely or erroneously think plaster seals water. In fact, you don't have to plaster concrete at all if you don't care what the surface looks like.

There's a lot of confusion on concrete as well. A lot of people think Gunite or Shotcrete refers to the plaster. It doesn't. They're just trade names for spray application of concrete. Whether you pour concrete or you apply Gunite or Shotcrete, you end up with the same thing, a concrete shell. Gunite or Shotcrete are no stronger than poured concrete unless you use a weak concrete mix.

I built the pond like you would a swimming pool. I used swimming pool parts, instead of pond parts, like the main drain, skimmer and auto-fill. When I compared parts, I found pool parts to be a lot more durable, while surprisingly lower cost. Also, replacement parts are easier to find than pond parts.

Oh hunh. When you list the ingredients of plaster, it makes sense that it doesn’t seal the concrete. It is, essentially, concrete with less sand. I am using portland cement and coarse sand right now at a ratio of 1:3. One less sand gives me plaster? I would still want a cake-frosting consistency?
Your pond area is beautiful! Thank you for sharing your expertise with me.

(ps… any advice on where to get pigment?)

 

[moocowman]

Actually, plaster ratios vary. You can make plaster anywhere from 1:2 to 1:3. So, what you're using for concrete could really be called plaster. When you lay it down thick, you call it concrete. When you spread it on a wall, you call it stucco. When you fill gaps with it, you call it grout. Traditional concrete usually has some larger aggregate in addition to sand, but coarse sand is a suitable substitute for gravel in a fish pond. You're not pouring a driveway or a house foundation.

My mom built 3 ponds just as you are doing; chicken wire and cement/sand. No plaster, no liner. The one she has at her current house is 5000 gallons, built about 10 years ago, never had a problem. This is how ponds/pools and fountains have been built for hundreds (maybe thousands) of years. I really shouldn't have bothered with the plaster in my pond. I tiled the upper 12" of the pond. Once the algae turns the walls green-black, you cant see the plaster anyway.

If you decide to plaster... You can get black and brown pigments from Home Depot or Lowes, usually sold as Quickrete liquid cement color. If you want other colors, Amazon sells concrete pigment. Cement is usually gray. So, you'll be mixing color with gray. You can get brighter colors by using white cement. White portland cement is available at some Lowes locations in my area, but Home Depot doesn't offer white portland at all. As for consistency, add as much water as you think you need to get a consistency where you can spread it on without it sagging or falling off. I know there's a science to water ratios, but again, you're not building a swimming pool for the Ritz Carlton. In reality, you're supposed to add that specific amount of water, then use "superplasticizer" (aka "water reducer") to make it more runny. Forget that stuff. You should apply it to concrete that's damp. Mist water from your garden hose to dampen the concrete. Plaster has a hard time hanging onto dry concrete, especially vertical surfaces. Once you're done applying the plaster, fill the pond right away. Plaster cures underwater.