New Pool Buyer, Deck Locking?

[bobwoodw]

Hiya,

So we've just purchased a new house (minus pool sadly) and we are now in the market to find a contractor. Living in the Phoenix AZ valley we have a lot of options. Recently we had a design appointment with one company that offered a special kind of construction in which they "lock" the decking around the pool to the pool shot-crete shell itself.

The way they explained it to us is that the area our home is in has "expansive soil" (the home builder talked to us about this as well) thus with a normal "floating" deck the deck and pool shell may separate, creating a crack between the inside edge of the pool and the bottom of the deck as the soil expands and contracts. With the locking construction re-bar would extend out of the pool shot-crete shell into the deck, locking the two together and preventing them from splitting apart.

The thing is even though the company has built thousands of pools in Phoenix I can't find any information online about this locking construction and I'm wondering if it really is a good idea. I would like to avoid having to monitor the inside edge of the pool for separation from the deck constantly, plus we were told with the lock if water did manage to get between and cause a crack it would be covered under the pool contractor's warranty unlike with the floating deck where none of the contractors we've spoken to would cover that normally.

The company is Shasta Pools located here in Phoenix. Has anyone dealt with this type of construction before?

[quantumchromodynamics]

Ask the company for a few references where similar construction was done so that you can see how the work holds up.

One of the purposes of an expansion joint is to allow for expansion and contraction without overstressing the concrete. The concrete shell and decking would have to be upgraded fairly substantially in thickness, rebar diameter and spacing, and concrete strength.

You might want to hire an independent structural engineer to review any proposed construction plans. A few questions:

01) Will this be a cantilevered deck?

02) What size, shape and depth pool are you considering?

03) Are you considering a vanishing edge?

04) How far out do you want the concrete deck to extend?

05) Are you considering an automatic pool cover?

06) What is your water table (will they hit water when they dig and at what depth)?

07) Has the pool builder given you any specifications on structural details such as concrete thickness, rebar diameter and spacing, and/or concrete strength.

[bobwoodw]

Ask the company for a few references where similar construction was done so that you can see how the work holds up.

One of the purposes of an expansion joint is to allow for expansion and contraction without overstressing the concrete. The concrete shell and decking would have to be upgraded fairly substantially in thickness, rebar diameter and spacing, and concrete strength.

You might want to hire an independent structural engineer to review any proposed construction plans. A few questions:

01) Will this be a cantilevered deck?

02) What size, shape and depth pool are you considering?

03) Are you considering a vanishing edge?

04) How far out do you want the concrete deck to extend?

05) Are you considering an automatic pool cover?

06) What is your water table (will they hit water when they dig and at what depth)?

07) Has the pool builder given you any specifications on structural details such as concrete thickness, rebar diameter and spacing, and/or concrete strength.

Thanks for the detailed answer, here's most of the extra info you asked for.

1) I don't know if it will be cantilevered but I will be asking that now and will let you know.

2) We're looking at doing a small pool, about 390-400 sqft of surface area, pretty much square with just a few odd spots in the perimeter, 4,5,4 depths.

3)No vanishing edge.

4)We discussed this with another builder and he mentioned the decking might crack in a locked system if the decking extended out past the edge of the rebar that was connected to the pool shell (because that decking would shift and the pool shell wouldn't) so we decided if we went with this option we would be separating off sections of the decking from the decking surrounding the pool.

5)No on the automatic pool cover.

6)I'm not sure how high our water table is, but it being Arizona and since we have had no warnings I would assume it won't be an issue, I am going to check with the house builder on that today.

7)I don't know the concrete or rebar thickness information, we were told that they add a fiberglass-like reinforcement to the concrete however to increase its strength. I believe the rebar spacing was going to be 6-12' varying depending on the location within the shell.

Thanks again! I've been looking for friends that have worked with the company that might have gotten this but I never would have considered asking the company themselves.

[Dreamscapes Pools/Design]

Due to the fact I do not design or build pools in Arizona, I cannot say in your area it is completely wrong. I will say any competent engineer or designer would be against tying the deck to the pool. In colder climates it is absolutely never done because the freeze/thaw cycles. A deck can crack a pools beam when the deck rises and the pool "which is far below the frost line" remains unchanged by the cold.

In a normal weather climate I could forsee the deck cracking as it moves and the pool of course does not. Especially if your contractor says you have unstable soil. You would create a fulcrum point just beyond the beam or where the rebar extending from the pools beam stops. The only way to 100% protect yourself would be to tie the entire pool deck to the pool shell with #3 rebar. This would be expensive and a waist of material. An expansion joint is the normal way of dealing with lateral movement of the patio deck. As well if the pool deck is cantilevered the deck contractor MUST use a bond breaker. You can use felt paper or similar plastic sheeting to create the bond break. There are plenty of free profiles online you can review.

If there is a soil instability issue in your area, why does the contractor think your pools shell is safe? Get a soil compaction test "not too expensive" to verify which points in your yard are suitable for the structure. You can do this without hiring an engineer and give this information to your prospective pool designers.

[quantumchromodynamics]

I don't think that tying the decking into the shell is a good idea. This will cause a lot of stress in the concrete and the concrete will crack unless it is very thick and strong and there is a lot of large diameter rebar.

Unless the concrete is one monolithic pour, the rebar will be exposed to corrosive air and water at the interface. This would cause the rebar to begin rusting unless it was stainless steel.

...we were told that they add a fiberglass-like reinforcement to the concrete however to increase its strength.

Note: some contractors will say that fiberglass additives in deck concrete are good enough and that rebar or wire mesh is not necessary. Rebar or wire mesh is needed to provide an equipotential bonding plane. Without an equipotential bonding plane, you are at risk for people getting shocks while getting into or out of a pool. Insist on rebar or wire mesh in the concrete decking.

If soil expansiveness is an issue, there are measures that can be taken to mitigate the risks. One option is to over-dig the area and backfill with a less expansive material. This will give you a buffer that should be able to isolate the concrete from the soil movement.

I recommend that you consult with an independent engineer, such as a structural or geotechnical engineer to help you design something that is going to last for a long time with minimal risk of problems.

[bobwoodw]

Thanks everyone!

I did some more research and hunted down a few more companies today. From everyone I'm talking to the company that does the deck "locking" usually ends up with cracks about 18 inches from edges of the pool, one designer I talked to even showed me some pictures from a remodel they are doing of an older pool from Shasta. Granted with a concrete deck there will be some cracking over time but this was honestly a complete crack around the entire edge of the pool.

The expansive soil is apparently not enough to cause major issues with the pool shells themselves, they do have to do extra reinforcement. The company I talked to today recommended paver stones instead of acrylic or concrete deck to minimize any damage from the soil shifting under the deck. The paver stones look great and are actually very affordable (the place that showed them to me said the upgrade for the standard 240 sqft they put around the pool edge to the nicer paver stone I liked was only about $200, if I went with tumbled cement paver stones it would actually be the same price as their regular decking). When I discussed it with my housemates though one was afraid because of how the paver stones are laid down without mortar of any kind that the pool would get more water behind the shell in the soil and there might be a bigger chance of cracks occurring in the pool itself.

We've pretty much decided to steer clear of the locking deck and the company I spoke to today has an amazing warranty (covers pretty much everything and can be extended from the regular 3 year to warrant the life of the pool). I checked their BBB and ROC reviews and while they do have some complaints, all complaints have been successfully resolved and they have less complaints then the other companies I've looked at.

I guess my next question, has anyone used paver stones as decking and how did it turn out? Have you noticed any issues with the pool shell that may be linked to the paver stone decking? I know the cement pavers can get really hot here in the summer but the ones I was looking at that I liked are travertine (a kind of limestone) that I'm told doesn't retain heat as much. I'm still trying to find more information on the heat retaining properties specifically.

Thanks again to everyone for responding, none of us have ever owned a pool so we're literally putting ourselves on the line based on what we can research and get by word of mouth.

[quantumchromodynamics]

I don't personally like the paver stones that are set in sand and don't have any grout. The pavers are usually brushed with sand to fill in between the stones. The sand tends to be a continuous nuisance. The cracks between the stones tend to get mold or algae and tend to trap dirt and water.

The stones can shift or sink. Drainage can be a problem due to the uneven surface.

The stones can give a good look and fairly good performance if they are very well done and properly maintained. They should be tightly constrained to prevent shifting. The sand should be properly compacted to reduce the chance of settling.

Note: This is mostly my personal opinion. I don't think that there is necessarily anything wrong with this type of deck if it is done properly. I know many people who have such decks and many of them are satisfied with the overall performance. Of course cost is an issue that has to be considered as well.

I am not familiar with your local soil conditions and I do not know how much of an issue there is with soil movement. Most of the time, with proper construction, concrete can be done in a way that holds up very well.

My preference for stones is to have a concrete base and for the stones to be mortared and grouted. This gives a much better, cleaner and more stable deck.

What size stones are you considering?

...the standard 240 sqft they put around the pool edge

240 Sqft. is a maximum of 2.65 feet width of decking around the pool. That is not very much. Is that accurate?

I would want at least 5 feet of width.

[bobwoodw]

The stones are just larger then the size of a standard brick but a little thinner then a standard brick, keep in mind the 240 sqft is just the decking around the edge of the pool so 2.6 feet is about accurate on it's width, we're thinking about adding more decking but that's all going to come down to price, we actually have a fairly large covered patio on the back of the house already so we're not too concerned with having more decking, though it would of course be nice to have another seating area.

The soil here is called "expansive soil", it shifts with heat changes quite a bit (enough to require by law that the home builder informs us about it before we sign any paperwork to buy) and from what we've been told it increases the required pool shell thickness and decking reinforcement, that's one of the main reasons I like the paver stones, while they may shift, we can just have them reset to smooth them again. I am a little concerned about drainage but I'm still trying to find out what the desired drainage is (how far from the pool shell wall before you can be considered "safe" against issues).

[ma23peas]

We are putting in a 20x40 gunite pool and using pavers (Belgard)...the key to installing them is using a reinforcing edge to limit any movement, compact the subground (we're using 4 inches of crusher run)...then once you put the pavers on top, leave a 1/4 inch between pavers or less, use a compactor on top of 2x10's that rest on the pavers to compact them about 1/4 inch into your substrate. Then use polymeric sand as your filler, it covers about 140 sq. feet per bag (depending on your pavers)...runs about 15-25 dollars per bag...the key to the polymeric sand is to only put it on when pavers are dry and there is no threat of rain....you will go through three passes and compacting to insure the sand gets deep into the cracks...but if the pavers get wet during the process you will end up with the beads sticking to the pavers and it's very hard to get off...after you have insured all the polymeric sand is deep and off the pavers then you use your hose as a mister and lightly add water which seals the bond of the sand and acts as a great barrier to weeds/mold/etc....

Hope this helps!

Tara