Doug Hoover's magic mortar mix

[Debra Combs-Planty]

Could I use Doug Hoover's mortar mix formula inside my pond to create a flagstone bottom?

 

[Big Lou]

What is Doug Hoover's mortar mix? A retail product?

 

[Debra Combs-Planty]

It's a mixture of on bag #45 thin set and two bags type S mortar mix for mortaring waterfalls and edging. Suppose to be very strong and waterproof. I want to know if it would last if I mortared a flagstone bottom in my pond.

 

[Mucky_Waters]

Before you do something you'll regret maybe you should discuss why you would want to mortar flagstone in the bottom of your pond in the first place? Flagstone in the bottom of the pond is not something commonly (or ever) done, and frankly seems like a lot of work and expense for nothing, so why do it?

 

[Debra Combs-Planty]

I don't like the look of the black liner. The sides are vertical because I am limited on the space I have for the pond. I planned on building a shelf around 3 sides that I would also like to put flagstone on. The one end will have a small stream from my bog filter and a waterfall from my mechanical filter, so the water turbulence should hide the liner. This is a second pond build for me, my koi grew too large for my first pond. I had flagstone in the bottom of my first pond, but it was not mortared in and too much muck collected around and under the stones. Trying to think of every angle before I start construction. Thanks

 

[Big Lou]

Alge, muck and other stuff will soon cover the flag stone like it does edpm. A lot of work for a little reward. Just my opinion.

 

[Meyer Jordan]

Regardless of any claims otherwise, I do not believe that any mortar mix will last if entirely submerged unless a sealant is applied.

 

[carolinaguy]

We used that mix in our last pond in our waterfall and our plant pond; however, that said we also coated it with a special concrete sealant used by the major water parks and dyed the concrete mix. Never had a leaking problem, but that said these were thick walls and reinforced with rebar. I'm not sure how thin the mix can be and resist cracking. If we were to design a stream between ponds, I would still use rebar reinforcing and concrete color in a 3 inch thickness at a minimum.

 

[Waterbug]

http://www.waterbugdesign.com/pond/sanjose_pond.html

I don't see why there'd be any problem, but don't know this specific product.

I use regular mortar and never had a problem. Especially on the bottom strength is certainly not needed. I don't "seal" any of it because the chemistry of cement means the CO2 in water seals the mortar/concrete in a surface reaction. In the DIY world yeah, boy oh boy, the myths are endless relating to cement. But if you want to use any "special" mix or apply any concrete sealer you should have fun. One small point to keep in mind is that before there was an internet there where millions of ponds using good old mortar/concrete and had been for hundreds of years. It's only in the past couple decades people have decided mortar/concrete has all these "problems".

Thin set is problematic on vertical sides as it takes so long to set the rocks generally don't stay in place. Real pain.

Also, some mixes could set too fast or be difficult to clean from rock.

I'd never use anything other than regular mortar, Type S, but even Type N is fine especially for the bottom.

DIYer's often get a little crazy with the "strength" thing. Better to use what's needed whether than "strongest". There are downsides to "strongest" like being harder to work with, brittle, etc...

I kind of agree with the point of flag stone on the bottom not really being a huge benefit because it becomes invisible pretty fast. Frequent vacuuming helps, and I find it enjoyable to vacuum just to see the rock appear. I prefer large river rock because the space of the rock still comes thru. I have used flag on vertical sides mainly because it goes on faster than smaller rocks. But I don't lay it like a vertical patio. Instead I put river rock, or other rock, between individual flag. The idea is a flag stone would look like an exposed boulder that's been eroded.

I would not use any steel in any cement over liner. In concrete ponds yes, the steel is protected from the water by having enough concrete between the steel and water to stop/reduce rusting. That's a lot of concrete. When I mortar rock over liner the rock touches the liner in spots so for the most part the mortar is thin.

 

[Big Lou]

I don't like the look of the black liner. The sides are vertical because I am limited on the space I have for the pond. I planned on building a shelf around 3 sides that I would also like to put flagstone on. The one end will have a small stream from my bog filter and a waterfall from my mechanical filter, so the water turbulence should hide the liner. This is a second pond build for me, my koi grew too large for my first pond. I had flagstone in the bottom of my first pond, but it was not mortared in and too much muck collected around and under the stones. Trying to think of every angle before I start construction. Thanks

Here is a perfect example of how the bottom will look over time, sorry.

 

[Meyer Jordan]

Regardless of any claims otherwise, I do not believe that any mortar mix will last if entirely submerged unless a sealant is applied.

I must correct myself on that statement as I was forgetting that there would be liner underneath. Thin-set mortar will work for this type application but for success, according to the mortar manufacturers, a 14 day cure time must be observed if product is to be submerged.

 

[Lisak1]

Why not just a shallow layer of gravel? Hides the liner, easy to clean and adds lots of surface area for beneficial bacteria... just a thought!

 

[carolinaguy]

Water bug makes a great point that the bottom liner will be covered by algae as the pond matures. No point in covering a liner with concrete and thin set over time.