Prerequisites for Steel:
The steel subs are responsible for putting in the steel
reinforcement bars (or rebar as its commonly referred to) in the pool to increase the tensile strength of the pool
shell. Without the steel, the pool shell would be much more apt to crack
under the force of the water and soil against it. Concrete has great
strength in compression, but it has little tensile strength. Steel has great
tensile strength, so the two are combined whenever large amounts of concrete is
present. The combination of the two is called reinforced concrete.
The steel subs use the plans drawn up by the structural engineer and lay
the steel according to the schedule. The structural engineering plans are
important because they let the steel sub know what kind of steel reinforcements are
necessary at each location throughout pool due to extra surcharging forces.
They crew showed up at the house a week before the plumbers were
scheduled to come in. When I heard the commotion, I walked outside and saw
them unloading their pile of steel rebar into the backyard. I had to ask
them to leave, telling them that the plumbers hadn't even come yet.
Unfortunately, both of the guys spoke no English. I guess after enough
hand waving, they got the point and left, but not before unloading their
whole pile of steel in my backyard.
I didn't see the crew again until the plumbers second day on the
job. The plumbers were close to finishing that morning (but not quite
done yet), when lo and
behold, the steel subs were back I called
the office and asked them what was going on. She apologized and said she
would take care of it. While I had her on the phone, I asked if it would
be possible to get a crew that could speak English. Since I was the acting
GC, I needed to communicate with them and I didn't know how to speak
Spanish. She said she could arrange it as they ran like 7 to 10 different
crews at one time.
Wednesday, August 28, 2002 - 12:03pm
I didn't call them back to schedule them in until the day after the plumbers had
completed their work. When I called that morning at about 8:30am, the
that she could arrange for a crew to be out about noon. That was pretty
cool - I didn't think they could be scheduled in that quickly. Sure enough, I heard work going on in the
back just after 12pm. There were three guys out there. The foreman/crew
lead was a guy named Juan. He had two helpers with him. Juan could speak
decent English and I was able to work with him pretty easily the two days they
were there. He said that typically its about a third of a day to do a
pool, but for my pool, since it had special engineering requirements, it would
be a full day. And because they started so late, they would have to finish
up the next day. Juan said that he had been tying steel for 8 years.
Given that he did anywhere from 1 - 3 pools a day, working 6 days a week, that
was anywhere from 2500 - 7500 pools! In the picture above, you can see the
tools of their trade: steel, wire wrap for tying, and concrete spaces to lift
the steel off the walls and floors. More on that later.
Some background on the numbers
Juan started on the spa while the two helpers started in the pool.
Typically, they start out by laying steel in one direction spaced 12"
apart. If the steel can't reach all the way across the pool in one
direction, they connect another rod to it, overlapping the first one by
2-3 feet and tie them together using wire. The steel rods comes in
standard lengths of 60' and are cut to desired length and bent as
required. Once they have steel running
12" apart all the way across the pool in one direction, they start in the
orthogonal direction (to get the criss-cross), doing the exact same thing. At the end of it, they should
have a 12" x 12" grid laid on the bottom of the pool. This 12" x 12"
grid is normally referred to as "12 on 12" or
"12 inch on center."
When I first started looking at the structural engineering plans, I
noticed a lot of notation that looked something like this: #3@12" o.c. What
I later found out was that this was the specification of #3 steel at 12 inches on center. And what that
specifies is the use of #3 sized steel to form a square grid that is 12 inches by 12 inches square -
also known as "12 on 12." #3
steel is a measure of the size of the steel rod that has a
diameter of 3/8" (#4 is 4/8" or 1/2" and so on). They told me that most pools
use #3 steel. #4 steel is used mainly where stronger reinforcement is needed (e.g. deeper
pools, or where surcharging
conditions exist), but for most cases, #3 steel is the norm. #3 steel
was what they used throughout my pool.
12 on 12 is the standard grid size for a typical pool here in AZ. When surcharging (weight bearing) conditions
exists on an area of the pool (e.g. the waterfall
area or where the pool is close to the house), the grid size has to be
smaller. Smaller grid size amounts to greater reinforcement (more steel per unit area),
which translates to increased tensile strength.
Examples of smaller grid sizes are "6 on 12" or "6 on 6."
As you can imagine, smaller grid sizes require more steel and hence more money. All steel requirements are defined by
the Structural Engineering plans. There's no guesswork as to how much
steel is enough. The plans and addendums will precisely define what type
of steel is needed (e.g. #3 steel), how small the pattern is (e.g. 12 on 12), and
at what locations in the pool.
The process went something like this:
They first create a 12x12 pattern of a single row of steel to fit the
contour of the entire excavated pool and spa.
Next, where the engineering plans calls out for it, they add
the extra steel to reinforce those areas that will bear extra weight.
In my case, there were sections of the pool near the house that called for 6
on 12. The spa was done 6 on 6. The waterfall near the top of
the pad was done 6 on 6 and from the waterfall to 5 ft out, it was done 3 on
They then "lift" the entire steel mesh up off the
ground and off the walls by 3 inches using small concrete spacers, so that when they shoot the shotcrete,
the rebar will ride in the center of the 6 inch shotcrete shell. If
the rebar was just laying on the pool floor, it would most likely end up on
the edge of the shotcrete, effectively negating any effect on increasing its
tensile strength. Here's a picture from a recent poolforum
thread that shows this problem.
Here, you can begin to see the 12 on 12 squares starting to form in both the
spa and the pool.
In the picture on the left, you can see another tool they use to bend the steel
- it looks like a crow bar, but there are teeth attached to the end that they
use to grip the steel to do the bending with. They hold one in each hand
and bend the steel like if it were made out of paper. This tool is
necessary because their are so many twists and turns inside of a pool. It
really is amazing to watch these guys work. They're like artists. It
reminded me of watching 3D animators at work. I used to work for Fox
Animation Studios in Phoenix as a Software Engineer. It was always
fascinating watching the 3D guys create wire-mesh models of solid objects.
It was so cool looking. It was a similar feeling as I watched these guys
work. The only difference was that they were bending and twisting steel
with their hands rather than doing it on a computer.
The excavation contours
serve as a rough guide for the subs when the steel gets laid down. They
basically just follow the shape of the excavation as a guide to lay their
steel. They follow the contour all the way up to the forms on the
perimeter of the pool. When they reach the forms, they bend the steel 90
degrees so that it points into the form. This final 90 degree turn towards
the form provides the extra
reinforcement needed in the bond beam itself.
When the steel
is laid down, they measure from the form to the steel and it should be 8"
to 10". Most of the time, its right at 9". If necessary,
they place little 3" concrete spacers between the steel and the ground to
make sure that the steel is floating 3" off the ground or wall. This
insures that the steel will be right in the middle of the shotcrete shell when
it gets shot. In fact, one of the things that the City Inspector looks for
during the pre-shotcrete inspection is that the steel is adequately off the
ground and right around the 3" mark.
The 3" spacers to
keep the steel off the walls are put in first. Once the entire steel mesh
is done, then they start adding the 3" spacers to the steel laying on the
bottom of the pool. You'll see that a little later in this page.
the pictures below you can see one of the guys starting to form the bench on the
back side of the pool. Notice that he is starting to put the concrete
spacers on the side to keep it 3" off the wall.
In these next few
pictures, Juan finishes the initial 12 on 12 pattern inside of the spa.
Notice that the rebar coming up to the form measures pretty close to 9"
from the form. He told me that anything between 8" to 10" is
acceptable. In the third picture, he starts to create the circular shape
that defines the spa by creating a pattern of concentric circles of steel.
also starts working on some of the benches in the pool. The first two
pictures are of the bench near the waterfall and last one is near the back of
the pool. Notice that the spacers are already in position on the sides,
but the whole metal cage is still sitting on the floor of the pool.
are a couple of shots with a larger perspective of the entire pool about midway
through the first day. Juan worked the spa and waterfall, while
his two assistants worked on the main pool area. You can tell what parts
of the job require more skill and experience. Those are the things the
foreman or crew lead usually does himself.
are some closer shots of the spacers and how they are actually tied to the steel
bars. The middle picture shows the steel just before they lift the entire
steel cage up 3" with the spacers on the ground.
they lift the cage up, one of Juan's assistants takes care of the light wells in
the main part of the pool. The steel is bent and criss-crossed in both
directions to create a small pocket or cavity that the electricians will use
later to hang the light against.
Juan's assistants brings piles of the spacers from the front and starts tossing
them down to the other assistant who starts to raise the entire steel cage up
off the floor and onto the spacers. When they're done, the whole cage is
off the ground by 3" and resting on the concrete spacers.
you see one of the guys start to turn the final 6 inches of steel 90 degrees
down towards the form. This provides reinforcement for the the bond beam
itself (as explained earlier).
Remember the situation with the waterfall pad not being stepped
up during excavation? (see the waterfall
pad schematic to see how it needed to look) I told Juan about the
"missing" step in the dirt. He said that it was not a
problem. He said he would mark the area that needed to be stepped up (to
+0") and create a little stair step with steel to mark it out. That
way, when the shotcrete guys come through, they'll see it and know to create a
step. The picture below to the left shows Juan marking the area out with
neon orange spray paint. The area starts 18" back from the edge of
the waterfall. That will give me 18" of shelf space for my submerged
boulders and the rest a step above in the back. The picture in the middle shows
Juan and an assistant creating the -9" shelf of steel all the way to the
back of the pad. The picture to the right shows the finished -9" step
that's been raised off the ground by 3". Tomorrow, he'll create a
little stair step at the orange line to go up +9" so that it ends up at
+0" (actually -3" since the steel will ride in the middle of the
concrete that's poured. The top of the concrete is really what's at
+0"). Effectively, their will be a dual row of steel there on the
+0" step up area.
a pool without a few tense episodes? Right after Juan finished up the
waterfall area for the day, he finished up the spa work (12 on 12 only with the
6 on 6 special engineering for tomorrow). The picture below on the left is
what I first saw. After staring at it for a while, I asked Juan,
"Isn't that spa wall high? I mean if I'm trying to get submerged
boulders into the pool, wouldn't it look odd that from the waterfall area to the
spa, there's this huge 12" high wall of all of a sudden? How are the boulders going to
natural flow into the spa if the spa wall is so high?"
asked him if he could cut down the spa wall like 6 inches or so that the
boulders could gradually descend into the spa. He said that if he did
that, I would lose my spa wall and the water from the spa would leak into the
waterfall area. He said that the wall needed to be that high to keep the water in the spa and
there wasn't much he could do about it. It was pretty late at that point
(6:30pm) and I knew the guys were tired. I knew they still had a bunch of
work to finish. Juan said that it would take them no more than a few hours
to complete the job. I told him I was going to call the rock work sub and ask him how
this spa wall should look like to make the waterfall into the spa look more
graceful. He agreed. He said he had another job up north to take care
of on Thursday, but that he would be back first thing Friday morning to finish
the steel. I told him that would give me enough time to get with the
rockworks guy to get a definitive answer.
By the end of the day, they had managed to complete the
Entire general pool area including benches, light wells, and
first step (2nd and 3rd steps are not steel'ed) with 12 on 12.
About half of the area near the house that required special
engineering (6 on 12).
Entire spa with 12 on 12.
Waterfall pad with -9" shelf only (used 6 on 6 at top
Spa with a 12" high wall near waterfall that needs to
be modified somehow =)
Here is a view of the finished work at the end of the day from a
few different macro perspectives:
Tomorrow they need to finish up the following:
Entire spa with additional steel per special engineering
schedule (6 on 6 throughout)
The other half of the area near the house that required
special engineering (6 on 12)
The waterfall step up 9" to +0" elevation to form
the back of the waterfall pad.
The modified spa wall per Rock sub's recommendation.
The front of the waterfall area per special engineering
schedule (3 on 6 from waterfall to 6 ft out)
Thursday, August 29, 2002
It actually worked out really well that the steel guys had to do another job on
Thursday. Unbeknownst to me, Jayson, my rock sub, had made prior
arrangements to send someone out on Thursday to pre-site my job. His pre-siter
was planning to take pictures of everything on Thursday and that way he could
figure out what the best course of action was before calling me back. Here is what the unmodified
waterfall pad looked like when the steel guys finished up on Wednesday.
You can see how we go from +0" elevation on the main part of the waterfall
pad all the way to +12" elevation at the spa wall. What I wanted to
achieve was a natural look where the elevation descends evenly from highest point
(the back of the waterfall) to the front. I have a nice elevation descent
from the waterfall into the pool (+0" -> -9"), but the waterfall
into the spa goes from +0 -> +12" which goes up - not down!
Here's some pictures of it from the side view near the
spa. On the left you can see how it goes from +0 to +12. The picture
to the right give a slightly different perspective, but you can see the steep
Friday, August 30, 2002 - 6:15am
By late Thursday night, Jayson had still not gotten back to
me. I left him a message on his cell to call me back. Friday came and the steel guys were back bright and early.
They arrived at about 6:15am. I told Juan that Jayson had not called back
yet. Fortunately, they still had a bunch of other work to do so they they
started working those things first. They continued working on the
waterfall special engineering which called for "3 on 6" near the front
of the waterfall and the "6 on 6" in the spa. Here are some
pictures of that work (notice how tiny the squares in the front of the waterfall
bench area is - thats 3 on 6!):
(Funny aside, I called the office a few days after steel was
done to get the final pricing and the admin there told me that she has rarely to
almost never seen 3 on 6 used before on a pool. I just kind of
chuckled. I thought about my waterfall area (picture above to
right). Later when I was talking to the rock sub and asking him whether
Lanny (my Structural Engineer) would approve of having extra large
boulders in a particular area in the waterfall. Before I could get the
name "Lanny" out, he said, "Lanny? Lanny
wants so much steel in that area that it could survive a nuclear
bomb! Don't tell me about Lanny." Hehe. I don't
mind paying a little extra for the peace of mind knowing that if an errant scud
missle landed on the waterfall, that it would still be standing.)
I tried calling Jayson again about 7:00am and this time he
answered. I asked him what the verdict was. He told me that
the best thing I could do is to try to "pull back" the spa wall so
that it wraps around the PVC source pipe for the spa. I asked him if he
could FAX me a picture. This is what he sent me:
I liked it the moment I saw it. Now the highest point of
the waterfall was at the back of the waterfall rather than at the spa
wall. Also, there is a little +3" rock pocket in the spa area that
will give it another intermediate level before it goes into the spa. I
gave it to Juan and he started on it right away. He wasn't pleased by this
change. This was quite a bit of work for him to do. For him to make
the change, he now had to effective elongate the spa wall back further by about
7 feet until it reached the spa waterfall feed pipe. He had to effectively
make a foot high steel cage that was 7 feet long. He also had to cut down
the existing wall. Yikes!
Here you see the guys begrudgingly start to cut down the 12"
wall, and start pulling the spa wall back towards the spa waterfall pipe.
Here you see them starting to form the huge 7 ft cage that will
serve as the highest point for the spa rock waterfall.
After about 3 hours of work, they finished it. Juan had me
call the office to make sure Don knew about the change. I called Don and
he said he would only charge me an extra $60 for their labor. What a
deal! Here are
various views of it from different perspectives. You'll notice from the
first picture on the left (staring into the little +3" spa rock pocket from
inside the spa) that the highest point of the waterfall has moved from the spa
wall all the way to the back where the spa waterfall pipe is sticking up.
You can get a better glimpse of it in the middle picture. The picture to
the right shows you a side profile of all the elevations. The bottom left
picture shows you a great view of the pool bench near the waterfall, and the
-9" shelf going up to the +0 shelf. The last picture is from the
One thing you may notice is that the spa dam wall between the
spa and pool has a little notch in it so that the water can flow from the spa
into the pool. The wall on either side of the spa is supposed to be higher
than the notch. Well, the wall on the side of the notch next to the
waterfall area was accidentally cut down to the same level as the notch.
Juan reassured me that the shotcrete guys would just put concrete there with no
problem. No steel was required there. There wasn't going to
be a rock load sitting on the wall, so an extra 6 inches or so of extra concrete
wouldn't require extra steel for it.
That's it for the steel work. They were done by about
11:30am. Now the plumbers could come in for the remaining spa dam wall
work while the electricians could do the electrical rough. The electrical
guys actually showed up just before the steel guys left, so there was a little
bit of overlap. That's Ok though - kill two birds with one stone.
Shotcrete is right around the corner!
Problems with the Steel Phase / Things I would
have done differently:
- I would have paid more attention to the waterfall pad area into the spa -
specifically with the spa damwall. Not having done this before, I just
thought the rock guy just piles some rocks back there. I had no idea
you have to create different elevated levels to make it look nicer. At
the end it was what I wanted, but not after considerable re-work and a lot
of aggravation on Juan's part. Still, he took it like a real
trooper. I tip my hats to these guys. They are true
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