Patio block coping question (alternative to polymeric sand?)

[Websherpa]

I am having a contractor re-do the polymeric sand in our pool deck, but the original pool contractor (who did both but is now long gone) used polymeric sand between the coping stones (essentially really large heavy coloured paving stones by techo bloc, the blocks have a purposeful consistent gap built into the stones). I personally hate it (in the coping) because it molds and goes green and I am assuming now needs to be replaced every 5 or so years, plus it will wash some sand into the pool each spring as the polymeric sand (essentially sand and hard jello) fails.

But I wonder if the polymeric sand solution is still worth my hating it vs. having my contractor do some other coping mortar treatment? And what alternatives should I consider before going with the contractor's recommendation? (Non-pool building but professional contractor that does have patio stone experience.)

Thank you for any insight or experiential opinions you can provide!

 

[jamjam]

If you post a picture of your coping and pool deck it would help. Are you saying the coping and pavers are one in the same and the joints for your coping are packed with poly sand?

 

[Websherpa]

Yes, the coping is made of large Techo-bloc paver blocks (PL'd to the concrete pool edge underneath).

Good idea, I hadn't thought about pictures. You can see the blocks and the polymeric sand grouting between them (and how it overhangs the pool between blocks where sand eventually wears off into the pool, harder to keep clean than a mortar grout since, being a polymer, it wears out quickly).

It looks good when it's first done (it's kept in the paver edge using tape until the polymeric sets). And as good and convenient as polymeric sand is, it eventually becomes a perfect petri dish for vegetative life, lol.

(In case anyone is curious, I Borate my salt water pool, best move ever!)

 

[jamjam]

why not use type s mortar between the coping stones? Or some other form or cement based joint?

 

[Websherpa]

Yes, that is what I am trying to get opinions on (advantages / disadvantages) of mortar types. Although cement mortar is the time tested option, our seasoned pool contractor chose polymeric sand for reasons I can no longer discover.

I just don't want to jump from the pan into the fire given the added labour cost, that it's a salt pool, and we have a wide temperature range both daily and seasonally here in Ontario, Canada.

 

[jamjam]

I am in NY and I did my joints with type S mortar - mixed with an additive. That is kinda the standard I think. You don't want your joints with anything that is higher strength than your adhesive because then you can get your coping to pop during freeze thaw cycles - You could go with an epoxy grout or some other type of product. Pointing them with type S mortar is definitely something a homeowner can do if installation costs are a concern. I did my whole pool for $8 in materials.

 

[Websherpa]

Hmmm... yes I can see that a thin set type mortar is also used. I know for some kinds of joints subject to expansion/contraction (say as between a cemented edge and block on a sand bed) some use a synthetic polymer self-levelling compound (with polymeric sand sprinkled on top for "look") which would potential last longer and certainly be more waterproof than the polymeric sand.

I guess polymeric sand was used simply for speed of application (and a continuous look to the mortar).

Every opinion here has and will be helpful to my final choice. Thank you!

 

[Websherpa]

Hmmm... yes I can see that a thin set type mortar is also used. I know for some kinds of joints subject to expansion/contraction (say as between a cemented edge and block on a sand bed) some use a synthetic polymer self-levelling compound (with polymeric sand sprinkled on top for "look") which would potential last longer and certainly be more waterproof than the polymeric sand.

I guess polymeric sand was used simply for speed of application (and a continuous look to the mortar). ADDED: And it helps prevent cracking due to minimal expansion and contraction (likely avoiding the need for a true expansion joint between coping and patio).

Every opinion here has and will be helpful to my final choice. Thank you!

 

[jamjam]

between two structures you want a flexible joint - the polymeric sand that is behind the coping can probably stay as it should be forgiving - but between the coping stones since they are presumably on a shared substrate and are "locked" together they can use mortar between them. The poly sand is really not what you want because as what you discovered is that with nothing significantly binding it it will migrate to the pool. You could also look into a penetrative sealer that will lock the poly sand in.

 

[rstrouse]

You can probably find sanded epoxy grout to match the polymeric sand.

 

[jamjam]

i wonder if he could maybe even go with a grey mortar and then embed the sand to match - i was looking into epoxy grout but was dissuaded as the application I was told is much messier.

 

[Websherpa]

Lots of great ideas here (and I found a few more people in similar shoes in TFP forum posts). "Sealing" the polymeric is one (we're sealing the coping and patio stone too, but I am thinking we need to do a penetrating sealer for the coping joints first if using the polymeric sand again to help lock it in.

Sanded epoxy grout is an interesting option too that meets a couple of the aesthetic and practical watershedding needs.

It's occurred to me that polymeric sand, being water absorbing, isn't the best coping grout given that some water accumulation and freezing can occur - especially as it erodes (the PL adhesive used for the coping blocks is probably more forgiving than mortar though).

IN any case, I don't want to be second guessing another pro's options, but fully educated in options certainly helps.

 

[Orion7319]

I’m no expert at this but I believe it has to do with rather or not the pavers are dry laid or in a mortar bed. If they are dry laid on top of a sand bed, I believe that’s when they use the polymeric sand. If they are set in a mortar bed on top of a concrete slab, that’s when they can use mortar. I think that’s how that works anyways…

 

[jamjam]

I’m no expert at this but I believe it has to do with rather or not the pavers are dry laid or in a mortar bed. If they are dry laid on top of a sand bed, I believe that’s when they use the polymeric sand. If they are set in a mortar bed on top of a concrete slab, that’s when they can use mortar. I think that’s how that works anyways…

My best guess is that the pavers used as coping are mortared down and the poly sand was used because it matches the rest of the pool deck

 

[rstrouse]

I'm not gathering how making a 1/4" mortar joint will be less messy. Both applications will require forcing it into the joint then damping it off the get the desired effect in the joints. In order to do that you will need a pretty thin mortar. I don't have freeze issues but my travertine coping has 3/8" grout lines and it grouted in with epoxy grout. 10 years and no issues whatsoever. That being said waterline tile for most pools is set in epoxy grout without freeze issues.

 

[Websherpa]

Orion7319 - I am relatively certain that the coping blocks sit in PL Adhesive on top of the cement pool surround (steel wall vinyl pool with cement bottom and surround). They join to tamped gravel bed (a modern angular screening stone that I forget what it's called) laid patio stone, so the polymeric sand certainly works there, and as a bit of an expansion joint between it and the coping stone. I guess I will need to magnify the construction pictures I took 6 years ago again. Hope I caught that portion.

 

[Websherpa]

i wonder if he could maybe even go with a grey mortar and then embed the sand to match - i was looking into epoxy grout but was dissuaded as the application I was told is much messier.

One thing I have learned from filling expansion joints in my garage floor (with self levelling polymer) is that a couple rolls of painters tape to line the top edges goes a LONG way towards "neatness" on any wet type mortar or caulk.

(For the polymeric sand option, they simply sweep it in then blow the remaining dust / sand off the surface and out comes the sprinkler to set it. Fast and easy but I'm thinking not the best option.)

I'm leaning towards the sanded epoxy grout route, if it's waterproof and blends in reasonably well, then it seems to fit the bill. The only draw back I see is the potential for any gaps at bottom filling with water from the coping edge and then popping the epoxy during a freeze (which is less likely with polymeric sand, but a consideration with any mortar).

 

[jamjam]

I'm not gathering how making a 1/4" mortar joint will be less messy. Both applications will require forcing it into the joint then damping it off the get the desired effect in the joints. In order to do that you will need a pretty thin mortar. I don't have freeze issues but my travertine coping has 3/8" grout lines and it grouted in with epoxy grout. 10 years and no issues whatsoever. That being said waterline tile for most pools is set in epoxy grout without freeze issues.

i sealed the tops of my coping then did a mix on the dry side and packed the mortar in with a tool - i then used a paint brush to sweep away any loose mortar. It was super fast and easy - granted I never got to prove or disprove the advice I got regarding the epoxy grout which is why I still recommended it to him in my one of my previous responses as an option to explore.

 

[Orion7319]

Orion7319 - I am relatively certain that the coping blocks sit in PL Adhesive on top of the cement pool surround (steel wall vinyl pool with cement bottom and surround). They join to tamped gravel bed (a modern angular screening stone that I forget what it's called) laid patio stone, so the polymeric sand certainly works there, and as a bit of an expansion joint between it and the coping stone. I guess I will need to magnify the construction pictures I took 6 years ago again. Hope I caught that portion.

If that’s the case then I would second the opinions of going with an epoxy grout for the coping blocks and keep the polymeric sand everywhere else.

 

[Websherpa]

I just checked the build pics and I photographed everything else in detail EXCEPT adhesion of the coping slabs. lol. I'm still guessing PL as I saw it used elsewhere with the same slab on other edges and can see no tell-tail mortar peeking out from under the stones in the production pics. (The original contractor here didn't mechanically tamp the screenings, so I suspect that's part of the reason we had a lot of heaving in the past couple years and hence the reason this pool patio is being re-done.)

Ok it's remarkably hot here today, so I am off for a swim! Thank you everyone!