Crack in the deck & crack in the pool

[Mike0893]

Hello all,
My pool deck has had a crack in it ever since we've owned this house (3 years). Since Spring I've noticed this crack getting bigger. It's now about 1/2" wide and extends under the concrete where it connects to the tile. I also have a crack in the pool plaster and I suspect they are related. In the center of this area I have a skimmer that the leak detection company says is leaking (about 1" of water a week) at the bottom elbow (they are coming this week to repair).

I have a couple of questions. Could the leak in the skimmer be causing the soil in that area to expand so much as to move the deck and cause the deck crack to get bigger.

The second question is how do I repair this? It looks like someone tried to repair the deck once before but now the crack is wider and deeper. What can I do the fix the gap between the cantilevered concrete and tile? What to do about the crack in the pool plaster?

I've posted some photos so you can see what i'm talking about. Thanks in advance for any input.

 

[ajw22]

Please post some wider pics of your pool and deck so we can orient where the cracks are and see the surrounding area.

 

[Mike0893]

This is the south area of my pool. From the crack closer to where I took the photo the deck has not moved. You can see the skimmer lid along the edge of the shadow area. From the crack to the skimmer and then another 8 or 10 feet past the skimmer is the area where the deck has moved.

 

[ajw22]

@AQUA~HOLICS do you know if that area of CA has expansive soil that can lift the slab?

Are there any trees around that could put roots under that slab?

 

[Mike0893]

There are trees around the pool area but where that skimmer is located is about 40 feet from the nearest one. When the skimmer leak gets repaired this week I’ll be able to see what’s under some of the concrete and should be able to tell is it’s roots pushing the concrete or not.

We are located about 30 miles south of San Jose. The soil is black clay type I would think would be expansive but I’m no expert.

 

[ajw22]

My guess the slab is being lifted and tilted from where the crack is and putting pressure towards the skimmer. The weight of the slab is causing the cracks in the skimmer, tile, and plaster around the skimmer.

I think your only fix is to demo and replace that section of deck to remove the pressures on the pool structure. When you demo that area you will see what is going on under it and along the pool bond beam.

 

[AQUA~HOLICS]

I have a question about the deck crack in the last picture of the first set of pictures. Is the deck lifting or pulling away from its self or both?
My concern is the crack at the skimmer that continues down the wall of the pool, this is unusual for a crack to do this, I have seen it before and it was from movement of the pool shell that had cracked.
Expansive soil will lift more than pull and being that the soil is clay I would expect more lifting of the deck.
If the pool shell moved in the area of the skimmer this would explain the leak at the skimmer.

 

[Mike0893]

It looks to me that the slab in the picture you refer to is pulling more than lifting. The lift at the crack is about 1/4”. The pull is closer to an inch but I don’t know if the lift was there before the crack started getting big. The crack has always been there and someone applied some sort of caulk to cover it up. The lifting of the slab that you can see in the gap between it and the tile has the skimmer in its center. The area is about 20 x 10

 

[AQUA~HOLICS]

How deep do you think is the crack in the plaster at the skimmer?
How will the leak detection company going to repair the skimmer and are you looking into repairing the plaster?

 

[Mike0893]

I can’t tell how deep the crack in the plaster is. It’s pretty narrow. I don’t think I could shove anything in the crack to tell how far it went.

The skimmer repair will involve sawcutting a 2x2 or 3x3 hole in the deck, hammering out the concrete, remove the old skimmer and install a new one.

I don’t have any repair for the plaster crack planned. I was wondering if there some kind of diy repair I could do

 

[AQUA~HOLICS]

That’s the correct way to have the skimmer replaced.
DIY for plaster repair would be with a plaster patch dry powder mixed and forced into the crack and it can be done underwater.
Still my concern is that the plaster cracked while under water.

 

[Mike0893]

I guess we’ll see if the pool leaks after the skimmer replacement.
Thanks for all the input. I appreciate it

 

[AQUA~HOLICS]

I hope everything works out but if their is an underlying reason other than the skimmer leak it can be figured out and corrected.

 

[Mike0893]

Is there a particular product I should use for the plaster patch?

 

[AQUA~HOLICS]

This is what I would try.

 

[tstex]

Mike, how long has the skimmer been leaking that you are aware it's a leak and not just evaporation? The reason I ask is bc leaks, depending on their nature, can cause erosion and voids. This can accelerate shifting and movement. Muck more so w clay soils than sandy loams. My main home is 100% shifting clay; the ranch is 5ft of sandy loam b4 clay. So, I've dealt w both extremes.

First, you need to determine the root cause of shifts. If not trees, then it's usually wet and dry extremes. You can fill cracks all day long, but if you have further shifting, then the expansion causes add'l cracks and thus leaks. Concreate bonding agents [for cracks] can only be a solution if there's no more shifting. Almost 99% of crack/filling agents are not strong enough to keep the 2 substrates together in the event of more shifting. If they are really good binding agents, your original crack "could" stay sealed/fixed, and another crack could re-appear close by, but 95% of the time the orig crack just enlarges.

Next, where your plaster is cracking, can you follow that crack to your deck, then ascertain if this is a "high point" and it starts to lower on either one or both sides from the crack outward on the deck? Pressure type cracks remove soil and cause shift due to voids; slow, slow leaks do not displace soil but cause it to expand. My take is the wet side is rising and dry side falling, thus pulling apart....let's see what the guys say when they fix the skimmer.

 

[Mike0893]

tstex
I’ve had a suction side leak since March or April. It started off slow and slowly got worse. I’m now losing 1 1/2 to 2 inches a week. So as you know we’re in a drought situation around here so I have been watering the landscaping much less than in previous years. I have areas where my lawn now has pretty big gaps next to the sidewalk so that’s the shrinkage. The skimmer that’s getting replaced is in the center of the area where the deck in moving and the crack in the plaster is directly in line with the skimmer opening. That matches your thought that the expansion is the root cause of the deck movement and the crack in the plaster.

Soif If I stop the leak and over a period of time the soil dries out, it would contract and the deck would lower to its original height. I could fix the cracks at that time.