Cracking grout between coping stones

pgershon

Gold Supporter
Jul 15, 2012
281
East Hampton NY
21 year old gunite/plaster pool and spa. Pool area largely fill with piles below - reinforced with additional piles 11 years ago. Pool used to crack every year around shallow end skimmer - finally seems to have been fixed 3 years ago by redoing the rebar and reshooting gunite in shallow end. Had a few small cracks on pool side of wall between pool and spa repaired 11 years ago. No cracks there since.

I have needed to replace the grout between the coping stones on both the pool and spa every 3-4 years. Seeing it again this late summer, with small cracks in almost every joint. Experience says water will get in during winter freeze and expand, such that cracks will be larger next year and water will get under the coping stones and the tile. If I dont address issue this year, I'll have a bigger problem to address next year. Note in my photos that in some places, the crack extends from the coping stone joint to the grout between the pool tiles.

Any ideas why these cracks occur. Is there a better or worse substance to use for the grout that better deals with water and freeze? The coping stones have a large expansion joint away from the patio stones (which sit on concrete base). Is it possible that there is movement between th coping stones that does not manifest itself with cracks in the pool? Any suggestions on what I might do to correct?
 

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ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
28,445
Northern NJ
What specific material are you using between the stones?

Grout is the wrong material and too soft. You should be using Type S Mortar between the coping stones.
 

pgershon

Gold Supporter
Jul 15, 2012
281
East Hampton NY
I did not do it personally, but hired people so I cannot be sure. I believe we used white cement when the stones were re-attached in 2011 , and lacerate thinset 3 years ago when we re-did it again.
 

pgershon

Gold Supporter
Jul 15, 2012
281
East Hampton NY
Also, would an epoxy grout be a good option (my landscaping guy is strongly recomending Tec Power Grout TA-550)?

 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
28,445
Northern NJ
Also, would an epoxy grout be a good option (my landscaping guy is strongly recomending Tec Power Grout TA-550)?


Epoxy grout for where?
 

pgershon

Gold Supporter
Jul 15, 2012
281
East Hampton NY
Thanks. But why do you think I keep having issues with cracking? Is it likely because of the mortar or something else? I hate to spend another $10,000 or so redoing tiles and coping stones to have it last only another 3-4 years. There must be a better way
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
28,445
Northern NJ
Thanks. But why do you think I keep having issues with cracking? Is it likely because of the mortar or something else? I hate to spend another $10,000 or so redoing tiles and coping stones to have it last only another 3-4 years. There must be a better way

Have the correct preparation and products being applied by craftsmen.

That is hard to find in today’s world in many areas.
 
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pgershon

Gold Supporter
Jul 15, 2012
281
East Hampton NY
I've gotten bids from three different craftsmen. One thinks they should mix silicone with the type S mortar. Another suggested adding some epoxy to the mortar. General agreement is that the cracking comes from the coping stones expanding and contracting between hot summer and cold winter.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
28,445
Northern NJ
General agreement is that the cracking comes from the coping stones expanding and contracting between hot summer and cold winter.

I don't buy that. Pools that have the correct materials used don't have mortar crumbling in a few years. Every pool has their coping sitting out all year long.
 

jamjam

Well-known member
Jun 25, 2020
650
NY
I used type S on my bluestone coping earlier this year when i installed it in may (DIY) most of the seems are good, oddly enough, the ones i did around the steps where i modified the mortar is where i have a few cracks (and separation) in 3 joints. Honestly, packing them in with new mortar is not that hard of a job so i figure this is something i will need to touch up on occasion. You're definitely gonna get east hampton quotes from people who assume they can charge whatever they want for the job, i would just make sure they stand by their work. For the joints I have that cracked I am gonna knock out the mortar and re-do it again now that it is cooler outside so the mortar won't shrink as much while curing.