Gunite pool 5 yrs old - plaster started cracking at 2.5 years. Why? How to fix.

Sandiego5

Gold Supporter
May 17, 2018
2
Wichita/Kansas
Just checking if anyone has seen cracks of this nature on a gunite pool & could give any insights as to why this is happening and what to do. Builder has delayed responding to problem endlessly, and recently with various versions of “not my problem.” Extremely frustrated. Also have similar cracks forming below sunshelf and adjacent steps. Could pool water be getting in behind plaster from grout between rocks? This is where the crack began on the sunshelf. We did have water discovered under the pool during construction but installed a pump casing with pump during construction (for making sure water is evacuated below pool in case of repairs). Builder did not indicate this was any problem when building pool. Water surface in pump well consistently measures below depth of pool. We have shut off auto-fill to see if water is indeed seeping in from “pressurized ground water” (as builder put it). He predicted water level would stay the same if water is seeping in. Water level has gone down 1+” in 4 days. Any insights would be much appreciated.
 

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HermanTX

Gold Supporter
May 20, 2020
695
Katy TX
This is very unfortunate and alarming. When they installed the flagstone on the sunshelf - do you know if they put it directly on the gunite or on top of the plaster? My thought is that most rocks such as flagstone are porous so water can seep through it. If it is set on top of plaster than the plaster would seal it but if set directly on gunite then that could be an issue. Gunite is porous which is why plaster is applied to seal the gunite. What about the rest of the pool - does it show similar signs or is just around this shelf with the flagstone on top?
 

cowboycasey

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TFP Guide
Jul 3, 2013
4,333
Fletcher, OK
it sure looks like they installed the flagstone under water level and then did the plaster on the rest of the pool so water has been leaking under the flagstone and freezing > thawing > freezing and breaking the concrete.. As I see it, this is all on the pool builder as anything under the water level needs to be plaster...
 
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Sandiego5

Gold Supporter
May 17, 2018
2
Wichita/Kansas
Thank you so much for the input, yes, the Oklahoma natural stone was set before the plaster was installed, (as shown on a bubbler area with adjoining steps, below), all of which also have started similar cracks forming vertically from just below the rock surface, most often contiguous with a grout-joint between the rocks. We keep our pool open (circulating, water kept at 40 degrees) all winter so would not be due to freeze & thaw. I assume gunite may be leaching calcium as it comes in contact with the pool water, forming calcifications that push the cracks wider? Also assume we are looking at a total replaster in addition to repairing the cause of the problem? Pool is literally just turning 5 next month, and, as stated, builder has been avoiding this problem for almost 2.5 years when it started as a single vertical crack below sunshelf. (failure to return phone calls, constant excuses, “super busy,” “let’s wait till fall,” etc.) Horrible experience, though we absolutely love having a pool & swim every day we can. By the way, TFP has been a godsend in helping us maintain both pool & spa. So grateful. Whenever I dream of ditching all my technology it is always TFP that comes to my mind as the one thing I cannot do without. Thankful for any further input on this issue.
 

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HermanTX

Gold Supporter
May 20, 2020
695
Katy TX
Well if there is no plaster under the stone then that is where the water is seeping through and then moving down between the gunite and the plaster on the wall. The PB should know better that all the gunite needs to be sealed with plaster. Then lay stone on top of the plaster. Probably best to chip out all the existing plaster, remove the stone and replaster the whole pool.
Need to push on PB to own up to this. If he would have acted earlier, you may only had to redo part of the pool but being over 2 1/2 years like this you need to get some legal help possibly to get PB to the table to talk about rectifying the situation.
 

Stoopalini

Gold Supporter
Jun 8, 2020
420
Central Texas
Do you have any pictures of the bench and sun shelf, from just before the stone was laid on top?

Did the crew apply anything to the gunite before placing the flagstone on it?
 

Desert Dog

Well-known member
Apr 4, 2020
261
Alpine, Ca
What I don't like is how the stone over hangs. They could have put a sealer under the stone but with the way the plaster comes up and stops under the stone, water can penetrate through small cracks in the grout and then behind the plaster. You probably can't tell from my avatar but my stone is cut about two inches from the edge of the shelf. The plaster is then wrapped up to the top of the stone to create a seal. From your pic you can see the grout is cracked. I think the builder saw pics of stone in pools but was not really sure on how to properly do it. If you also have freeze in your area, that is a whole other issue.

But for the record. My stone is on gunite with a water proof membrane painted on. Then the mortar bed is water proof and the grout. Then the plaster is wrapped around the face to seal the end.