I own a home in Florida that has a crack in the concrete pool shell
near an upper corner, and I need to determine the best method of
addressing stabilization and repair. Let me try to explain the
configuration and what I think is going on:

The pool is rectangular, approximately 15' x 30', and is attached to
the back of a home that is at ground level in the front and one story
above ground level in the rear. Hence, one walks directly out to the
pool, which is set behind a one-story retaining wall. The long side of
the pool is parallel to the house, but the back pool deck is a
trapezoid, so the long dimension on the pool's side away from the house
does not run parallel to the retaining wall. At one end of the pool,
the retaining wall is approximately 3' from the pool edge and corner
and at the other end of the pool, the retaining wall is about 5' from
the pool edge and corner.

The pool is surrounded by concrete decking covered in Saltillo tile. I
assume the decking is tied to the pool shell via the extended rebar
from the pool, as I am told is common, but, as i didn't build the pool,
I cannot verify this without frther detective work.

At the corner of the pool (and there's one problem, it has a 90-degree
corner, not a round corner) at the end 3' from the retaining wall, a
crack has occured which runs roughly from the top corner at a 30-degree
angle downward and along the back wall of the pool. Part of this crack
is above the water line and part below. The crack is about 1/8-1/4"
and extends about 4' in length.

What I think might be going on (just a guess) is that the
expansion/contraction at the end where the deck is narrow and the
retaining wall nearby is such that it is causing the crack and
loosening tiles off the coping. The retaining wall does not appear be
moving, so i don't think that's the issue.

Now, I want to stabilize this deck/pool shell interface before making
further repairs. I wan to solicit solutions from experts, but had the
following idea, which is open to comment. I was wondering if I could
drill down about 24" through the decking at, say, 16" intervals
laterally, into the center of the pool shell and epoxy rebar into these
holes to further strengthen the decking-pool shell interface. Is this
a sensible idea? Others? (It would be helpful if the repairs can be
effected without destroying all the Saltillo decking, if possible.)

Also, I see an interesting new product, Torque-Lock
(http://www.askalanaquestion.com/torque-lock.htm), which looks like it
might have application. Does anybody has experience or comments?

Any and all assistance much appreciated. If anybody needs photos to
better appreciate the layout and design, I'd be happy to e-mail.

Thanks in advance.

First I would try chasing and patching, perhaps with wedges, to see if the
settling is historical and not ongoing.

If simple patching does not hold up, then you either have a flawed shell,
or a stress that a correct shell cannot endure, or both.

If the shell is flawed, you must excavate and rebuild it properly.

If unusual stress is the problem, you must also excavate.

http://www.askalanaquestion.com/torque-lock.htm

I really get skeptical of claims like "5000 lbs of torque" when what you
want is linear force, not torque, and when the material strength of
concrete in tension doesn't support but a tiny fraction of such boasted
forces.

I would think you could do just as well with proper excavation, sculpting,
and application of rebar bent into giant "staples" or "stitches", if will,
patched in with premium polymer-modified cement.

Thanks for the reply.

I don't think it's a settling problem, at least at this point. The
pool was built in 1989, and the crack was there in 2000 when I bought
the place. I tried to fix it by removing all tile in the area and
patching the crack with polysulfide caulk, which can be used in
submersible situations. I thought that polysulfide, which has great
elasticicty, would endure any slight movement. But, apparently, the
caulk has become delaminated from the concrete, rather than failing
through gross movement.

I cannot comment on the shell itself, except to say it was built by one
of the areas premier pool builders and is fine everyhwere but this one
location.

I was hoping that driving a bunch of rebar vertically through the deck
and into the shell wall would stabilize any stresses and movement that
might be occuring through uneven expansion. If that's a lame idea,
then I might try another simple repair, using polyurethane caulk this
time, which also can be applied for submersible use and which has one
of the strongest adhesions of any material, although its elasticity is
slightly less than polysulfide.

See your point on the Torque-Locks.

Thanks, again.

tacker writes:

I was hoping that driving a bunch of rebar vertically through the deck
and into the shell wall would stabilize any stresses and movement that
might be occuring through uneven expansion.

Think about it. If stresses are enough to pull the solid concrete apart,
they will tear any patch apart, the patch being necessarily weaker than the
original.

If the pool is not loosing water from the crack it is likely just a
normal concrete expansion crack and the plaster just makes it look
worse. When i moved into my house the old pool had cracks down the
entire shell, on two corners, and the deck had 6 inches of air under it
from 20 years of deck cracks letting florida rains pour in. Most shell
cracks will be caused by the cheap engineering of the deck tied into
the shell (decks settle from uncompacted fill,leaks,etc and pull on the
pool shell)....and concrete just cracks in general.

if you're not leaking i wouldn't worry about it. You can test to see if
the crack actually moves with a crack movement testor. But if you're
not leaking i wouldn't worry about it.

Even new pools get large cracks in the plaster....heck 1/2 the people i
know who had a new pool built have them...It takes a long time (year
even) for concrete to cure. So the plaster goes on too soon and the
concrete naturally has expansion cracks which carries to the plaster
sometimes.

I had a 6 foot crack down the pool bottom, and up two walls. I V'd them
out with an angle grinder, put hydrolic cement in the cracks and had it
replasterd with a plaster/quartz aggregate. I also replaced the deck.
Its been 5 years so far and no cracks have come back out.

Average lifespan of the plaster is probably 10+ years depending on chem
maintainenance. If you did have a leak you could always have those
fiberglass come in and coat your shell but that stuff in my opinion is
overpriced..fiberglass in water gets blisters, delaminates,etc. Luckily
we're in florida plastering is cheap.

- shawn