Flagstone on top of concrete deck?

[Household6]

Is it viable to lay flagstone on top of concrete?

Our pool (and it’s deck) have been around for at least 35 years. We are planning on selling the house within the next year and i think updating the pool would serve us well.

We haven’t sealed the deck as we should have so we now have some small cracks forming where water has gotten in. (I do not believe this is a structural or settling issue.)

Rather than rip up 300sf of concrete, and likely create an issue because we can’t tell where the pool coping ends and the deck begins, can flagstone be laid on top of the concrete?

I’m guessing we’d first need to repair cracks and reseal the concrete, then put down a layer of sand (how thick?) and compact it.

While most would use mortar between the stones, I’m wondering why not use sand and compact it between them? Seems this would allow for some shifting without cracks. Would probably have to add to and recompact every so often, but that doesn’t seem to be a dealbreaker to me.

Bad idea? Things to watch out for? What does the tribe say?

 

[Bperry]

Is it viable to lay flagstone on top of concrete?

Our pool (and it’s deck) have been around for at least 35 years. We are planning on selling the house within the next year and i think updating the pool would serve us well.

We haven’t sealed the deck as we should have so we now have some small cracks forming where water has gotten in. (I do not believe this is a structural or settling issue.) View attachment 544092

Rather than rip up 300sf of concrete, and likely create an issue because we can’t tell where the pool coping ends and the deck begins, can flagstone be laid on top of the concrete?

I’m guessing we’d first need to repair cracks and reseal the concrete, then put down a layer of sand (how thick?) and compact it.

While most would use mortar between the stones, I’m wondering why not use sand and compact it between them? Seems this would allow for some shifting without cracks. Would probably have to add to and recompact every so often, but that doesn’t seem to be a dealbreaker to me.

Bad idea? Things to watch out for? What does the tribe say?

Looks like you have a structural crack right near the steps that runs from the deck over the edge down into the pool? Haven’t seen anything like that design before.

 

[kimkats]

My worry about just putting sand down it it will get washed out in to the pool and surrounding area with rain and splash out from the pool.

 

[AQUA~HOLICS]

It appears that the deck and pool walls are as one continuous piece. This will add some additional work to correct the cracking/movement that’s occurring.

 

[Bill1974]

Are you sure you will see a return on this investment? You said you are planning on selling in a year. Any cracks in the concrete are likely to transmit through to the flagstone if they are not fixed or if they are decoupled.

 

[keithw]

You can certainly flagstone over concrete. I did the same to my pool. Here is a link for the project, New pool proj.Flagstoning around (and on) my fiberglass pool

I do not think sand would be a good idea. It will certainly run into the pool and since flagstones are not all the exact same depth and shape I could see them moving around too much. I would use portland as the mortar and the bed. But keep in mind that this would be a real labor intensive project. My pool took most of the summer to flagstone, working on it almost daily. There is a lot of cutting and fitting that is done with flagstone. But I too am concerned by the four cracks that run through the deck into the pool. Does the pool leak? I think you would need to address those cracks before you worry about the deck.

 

[Household6]

Looks like you have a structural crack right near the steps that runs from the deck over the edge down into the pool? Haven’t seen anything like that design before.

Agree it’s a very unusual install/design.

Pool dates back at least 40 years from what we have gathered from neighbors. (Folks in their late 60’s recall swimming in it as kids, but nobody remembers it being built.) No telling how it was installed or what was done! But what I’ve come to believe is the pool was poured and the concrete deck came later. They somehow rounded the edge of the deck to meet with the top of the pool.

The crack you are referencing has been there since we have owned the house in 2009. It stops right around where the water level is in the photo. There are other similar cracks around the pool all the same in where they stop. They’ve become more noticeable in the last few years due to us not sealing the concrete deck. So it’s the deck that’s at issue, not the pool.

 

[Household6]

My worry about just putting sand down it it will get washed out in to the pool and surrounding area with rain and splash out from the pool.

This is my concern too.
But when weighing the pros and cons, I think I’d rather vacuum up sand and fill in once or twice per year than deal with the stones cracking from not being able to shift a bit and having to replace them. Or am I missing something?

 

[Household6]

It appears that the deck and pool walls are as one continuous piece. This will add some additional work to correct the cracking/movement that’s occurring.

Years ago I thought the same and asked in the forum. Conclusion was that there HAS to be some type of coping, though it’s not obvious.

In places where the deck has cracked and goes over the edge, it stops around the water line. This leads me to believe the pool was poured and cured. Then the deck was poured and somehow the edge rounded where the deck and pool meet.

There are a couple places where a crack goes into the pool, but they were repaired by previous owner and only noticeable when the paint becomes thin and you can see the patch (no crack exists).
We paint the pool every 4 years (spending $2500) versus having it replastered ($30k) lasting 20(?) years.

 

[Household6]

Are you sure you will see a return on this investment? You said you are planning on selling in a year. Any cracks in the concrete are likely to transmit through to the flagstone if they are not fixed or if they are decoupled.

Gotta do something to make it more aesthetically pleasing!

I think (or am I naieve?) I can do flagstone easier than I can do a concrete recoat and stamp. Plus, doing the flagstone would allow me to break the cost and time requirement up over 3-4 months.

We will repair the concrete cracks and seal before laying flagstone. My hopes are that by using sand below and between the flagstone this would allow any shifting to go to the path of least resistance resulting in the stone not cracking.

 

[Household6]

You can certainly flagstone over concrete. I did the same to my pool. Here is a link for the project, New pool proj.Flagstoning around (and on) my fiberglass pool

I do not think sand would be a good idea. It will certainly run into the pool and since flagstones are not all the exact same depth and shape I could see them moving around too much. I would use portland as the mortar and the bed. But keep in mind that this would be a real labor intensive project. My pool took most of the summer to flagstone, working on it almost daily. There is a lot of cutting and fitting that is done with flagstone. But I too am concerned by the four cracks that run through the deck into the pool. Does the pool leak? I think you would need to address those cracks before you worry about the deck.

Wonderful! Thank you for the link!
See my replies to previous responses re the cracks.

 

[Bperry]

Agree it’s a very unusual install/design.

Pool dates back at least 40 years from what we have gathered from neighbors. (Folks in their late 60’s recall swimming in it as kids, but nobody remembers it being built.) No telling how it was installed or what was done! But what I’ve come to believe is the pool was poured and the concrete deck came later. They somehow rounded the edge of the deck to meet with the top of the pool.

The crack you are referencing has been there since we have owned the house in 2009. It stops right around where the water level is in the photo. There are other similar cracks around the pool all the same in where they stop. They’ve become more noticeable in the last few years due to us not sealing the concrete deck. So it’s the deck that’s at issue, not the pool.

Cracking like that is not seemingly cosmetic. Water can get through very small almost invisible cracks and cause havoc in the soil underneath. I had a similar issue on mine. The fact that the crack stops right about where the water like is may be more of a “the water stops where the crack is” because the water is leaking through that crack.

 

[keithw]

If you do plan on using sand then what you could do to minimize it getting into the pool is cement down and grout the ring of flagstone that will overhang the pool. Then you could do the rest in sand and any sand washing out would occur on the outside.

 

[jonpcar]

My 2 cents. I can’t imagine that flagstone over sand with hard grout between would stand up even for a short time…maybe not even long enough to get the house sold (haha), hard grout would start cracking immediately. And without hard grout to “seal” the sand “under”, a “sand ground” would definitely be all over the place including in the pool. I would consider pavers or travertine over sand with enclosing edges (especially coping) bonded down hard…

Here is my example:

COMPLETED: DIY Travertine Pool / Patio / Waterfall Remodel in AZ

Re: DIY Pool / Patio Remodel in sunny Arizona (lots of photos) Completing the Cap and Border Tiles / Cutting Tiles for a Curved Border At this point we had completed installation of 95% of the travertine Cap Tiles on the walls and the 6”x6” travertine tiles on the pool deck border. We wanted...

www.troublefreepool.com

But I agree with other posters…the cracks into the pool would be a huge concern for me and lipstick would not convince me that the pool is sound. I would let the next owner dream about fixing up their oasis. If you do all the work yourself, you may get your money back when sold, but here in Arizona you probably wouldn’t. Finally, if you are planning on doing the work yourself and have not done this kind of thing before, it is a LOT of work and a huge learning curve.

 

[Bperry]

I’d either spend the money to fix the pool correctly or not spend anything on it and sell the house as-is. A broken pool is a huge disincentive to new buyers. Most buyers will have a home inspector who will at least look at the pool and will probably point out obvious cracks (Mine did). Then the buyers might hire a specialty pool inspector (I did) who may end up being mostly worthless (mine was) in finding other problems or at least give them a repair estimate.

Letting a potential buyer knock the price down even $40k (that can be deducted from the sale price rather than the seller paying for repairs directly) would be a better alternative than the seller spending $10k cash putting flagstone down and then having potential buyers balk at the cracks and having to reduce the sale price anyway.

Conscientious buyers are going to be scared of a broken pool either way so I’d choose the option that cost me the least amount of direct cash outlay.

 

[Dirk]

Well, if you don't mind me sayin', leaving the pool as is and disclosing its problems to the next buyer is the right thing to do (the legal thing to do). Your pool and deck very likely have structural problems and filling in the cracks and hiding them from the next buyer, which is the result of your plan if not your intent, is not OK (IMO). Isn't that what the last owner did to you? Would you like the current owner of the house you're going to buy next to do something like that?

Your pool and deck are likely missing an expansion joint. That's a flexible joint normally installed between the two that allow the two to move independently (as they will always do), and be able to better withstand forces that would otherwise tear both pool and deck apart, just as yours are being torn apart.

The correct fix is to remove the deck, install a proper coping with expansion joint and new deck with rebar, and then resurface the pool. All that after determining that the cracks in the pool are not also in the underlying gunite, which is entirely possible.

Tell the truth to the next buyer and discount the sale price appropriately, so that they can remodel the deck and pool to their liking.