Hairline cracks on the outside wall

[averagejoe]

Howdy!

My pool has raised spa and the pool itself has partially exposed walls. I started noticing quite a few hairline cracks in the tile grout. On its own it would not raise much of concern, but later I noticed calcium buildup along these cracks. From my understanding the only way it would happen if water regularly gets into it and dries there. In addition, I noticed cracks in the coping stones' grout in these areas as well, so it appears to part of the same process.



A couple weeks ago I noticed something more alarming. On the exposed wall I have stucco and paint on top of the stucco. There are several very tiny cracks showing up through the paint. And all of them have the same issue - calcuium build up lifts up the paint until paint gives up and shows up as a crack. One crack I followed all the way from the tile grout to the soil level and confirmed that tiny crack shows up on the outside face of the gunnite shell. And again - same white buildup around it in there.



I am aware of shrinkage cracking. But the fact there is a white calcium buildup going on made me think it is actually a crack through the whole shell and not just a surface one. I did not notice cracks in the plaster, but plaster is pebbletec and it is somewhat hard to see around pebbles. Also, if my understanding is correct, plaster itself expands a little when under water, so it might hide these tiny cracks.

These cracks are also more noticable towards to top of the wall.

I am still trying to figure out if there is a leak, but the pool certainly does not lose a whole lot of water right now. Dye test did not show any significant water movement around tiles with cracks and calcium deposits. The way I found all these issues are white calcium buildup itself around all these tiny cracks (and there are quite a lot of them). Calcium deposits do not showup on the grout without cracks by the way.

I will certainly bring PB while it is still under warranty, but after the history of this project and their crappy overall work, I have little to no trust for them. So wanted to hear community's thoughts on these. Are these cracks going to cause problems long term? What would be the right handling of these?

PS: also, if someone could suggest how I could stop that calcium building up everywhere water dries - that would be great on its own =) It is very tough to get rid of even with SS brush, and I am wary of using acid for cleaning it off, as acid will eat out grout as well if I understand correctly.

 

[Arizonarob]

Hang tight Joe, let me ping a few of our construction gurus.

@bdavis466 @jimmythegreek @Pool Clown

 

[ajw22]

I think you have a combination of settling cracks in your grout which is no big deal and should be patched and efflorescence.

Efflorescence - Wikipedia

en.wikipedia.org

I doubt your pool is cracked or leaking. Some water may be getting into the gunite and behind the stucco from the grout cracks and causing the efflorescence. Fix all the grout and most of your problem should go away.

Every year or two I need to fix small cracks around the grout in my spa. It is part of normal maintenance around stone and tile.

 

[averagejoe]

Thank you @ajw22 for your insight! So the water collecting on the outside grout cracks is just wicking in from the spa/pool, and fixing these cracks should stop it?

Here are couple more pictures. builder/PB had to redo bonding in couple areas, so I took pictures while these were open. One is under the coping stone and one on the side wall (it was a concrete step covering it before). On the second picture white area is where the painted stucco is and below is a pool shell. This is also an area where the light is on the other side (the crack goes right at the center of the light housing vertically). They had to get into the shell to reach rebar to bond to. But that crack was visible in the stucco before they started working on it, so it is not the result of cutting out pool shell concrete.

 

[ajw22]

I can't tell from the pics what is old and what is existing and exactly where things are located.

All cracks and openings need to be sealed so that water does not get behind tile and stucco. Gunite is not waterproof and once water gets onto the gunite it migrates and eventually comes out somewhere as efflorescence. Water getting behind tile and stucco will erode and loosen tiles.

 

[simon SPRAGG]

I have seen thus a number of times, sadly often with new or reformed pools.
Start of my doing a saturation water test. Crucially you want to find out about calcium hardness.
Now the problem is (builders don't get this) is that tile grout contains calcium hydroxide. This has a high pH. So if the natural calcium level is low then the water dissolves the new calcium. You may then have tested the water to find the pH is too high and reduced it... Alas the water gets aggressive again and dissolves some more.
So in your case some grout has dissolved then got behind the tiles. Add settlement cracks then add chlorinated water mixing with air, turns back into salt. Also the calcium hydroxide that has dissolved in part will come out of solution as calcium carbonate stains.

Trouble with water testing is the test sample. If the pool runs 24/7 (varispeed pump) & yiu then take a sample by dragging a container in the net from one end of the pool to the other you then get a more accurate picture of what is going on.

Hope this helps


Simon

 

[simon SPRAGG]

The other clue is whether the tiles feel slightly rough. Which could also be calcium out of saturation... But again does not mean you have too much, easily could be a lack of Cal hardness...
I use Orenda tech (Google LSI calculators) download their app really quick and easy.
So set pH at 7.2 / TA @100 / Temp at say 22c and then you'll see Cal hardness requirement... Once Cal is correct the water will stop dissolving the grout, pH will stabilise and calcium carbonate stops forming....
Interesting...

 

[ajw22]

The other clue is whether the tiles feel slightly rough. Which could also be calcium out of saturation... But again does not mean you have too much, easily could be a lack of Cal hardness...
I use Orenda tech (Google LSI calculators) download their app really quick and easy.
So set pH at 7.2 / TA @100 / Temp at say 22c and then you'll see Cal hardness requirement... Once Cal is correct the water will stop dissolving the grout, pH will stabilise and calcium carbonate stops forming....
Interesting...

Welcome to TFP Simon.

We have our Recommended Levels - Trouble Free Pool and PoolMath that cover Calcium Saturation Index (CSI) - Trouble Free Pool

It could be aggressive water that degraded the grout if TFP guidelines were not followed. Often pool builders have their own ideas about water chemistry and it takes a while to get new pool owners to see the light.

 

[averagejoe]

The other clue is whether the tiles feel slightly rough. Which could also be calcium out of saturation... But again does not mean you have too much, easily could be a lack of Cal hardness...
I use Orenda tech (Google LSI calculators) download their app really quick and easy.
So set pH at 7.2 / TA @100 / Temp at say 22c and then you'll see Cal hardness requirement... Once Cal is correct the water will stop dissolving the grout, pH will stabilise and calcium carbonate stops forming....
Interesting...

That is a great insight, thank you! Tiles do not feel rough (yet?). I used to trust my local Leslie's water tests - the guy seemed to be quite knowledgable and really never even tried to sell anything to me, and his results matched my K-2006 tests in the past. And I have to do monthly water tests at the store anyway to keep my warranty with PB. But yesterday I pulled out my K-2006 and CH showed 400 and TA 140. I ordered speedstir and once it arrives will use it to make sure stirring is not an issue and will try your tip about putting container into the net and dragging it across the pool.

That been said, everything you described makes sense in regards to tile grout. These cracks going on on exterior wall, (thanks to calcium building up I can see them really well) - could water eat through the shell the same way you described water eating through the grout? I am not losing any noticeable amount of water, but my warranty expires this summer and I wanted to make sure these tiny cracks will not become something much bigger of an issue.

 

[Pool Clown]

One picture is cause for concern in two ways. It is the last picture that you posted.

First, the gunite should be fairly uniform from top to bottom when formed. Yours there is not. It looks as if rebound was used to fill in the area right next to the rebar, which is the second concern.

That rebar does not appear to have been chipped out to get to. IOW, that rebar, if it is supposed to be the pool shell's rebar, and what you needed to get to for bonding, should have been encased in gunite, and therefore should have had to have been chipped out to get to for bonding.

If this is a new build, put the PB on notice of the crack and monitor it. If it begins to open up, leak, or become offset, then it will need to be dealt with in a timely manner. A diary of pictures are best.

Question: Was this area the ramp into the pool when they were excavating?

 

[averagejoe]

I might be wrong (area already is filled in), but that could be rebar from the steps next to the pool. They needed to bond steps and I think the bonding wire was there, it was just not tied into the steps rebar. That been said, what you mention about rebound use - i think i saw at least couple places like that where concrete on the outside wall could be scraped with the hand. I pointed these locations to the PB and they cleaned it and filled it. But of course, I could not possibly find all possible places where they skipped on quality. And since the overall quality of the work was very low in my opinion, I would not be surprised to find anything =(

Not sure what you meant by "was this area ramp into the pool"? This pool was built on a slope, so it was partially excavated. Here is one of the pictures I have with it excavated:



And here is with all the rebar in place:



They screwed up and raised the whole perimeter walls by 2" using hydraulic cement. What you see under the skimmer hole goes all around perimeter, including spa (just not visible because of the tile:



This is opposite side of the wall where the crack on the last picture is visible:

 

[Pool Clown]

Most pools are dug having material on all sides. There needs to be a way to access into the pool while it is being excavated when using a loader (bobcat), that is what the ramp is for. Usually the ramp access is in the shallow end so there is as little form work to do as possible to close it up once the pool is dug. In your case, most of the pool was formed.