It's cracking because it's only 3.5" thick!

Paolo Benedetti founder of Aquatic Technology Pool & Spa
Vanishing Edge Pool, Infinity Edge Pool, Perimeter Overflow Pool, Slot Overflow pool, Knife Edge Pool, & Disappearing Edge Pool expert

I recently was involved in a construction defect case, where among the many flaws was a substandard pool deck. The flagstone veneer was coming loose all over the place & the grout was cracking.

When I dug back a part of the lawn at the edge of the patio - the truth revealed itself...

The concrete slab under the stone work was only 3.5" thick! To make matters worse, the concrete contractor used 4-5" of crushed dolomite rock for a sub-base. Dolomite rock is very soft crystalline rock that has virtually no load bearing value. And, placing such thin layer of such a fine sub-base allowed the underlying expansive soils to transfer their energy directly into the masonry above.

To add insult to injury, there was a geo-technical investigation (soils report) available to the concrete contractor. But he didn't bother asking if one was available. Now that it has been thrown back into his face, he wish he had asked for it! The soils report made recommendations as to how much of the expansive top soils needed to be removed, what was to be imported, and how the sub-base was to be installed. As it turned out there was supposed to be "24" of compacted 3/4" drain rock" placed under the slab. The report specified "a minimum 6" thick slab with #4 rebar on 12" centers, topped with #10 wire mesh, tied to the surface of the placed reinforcing steel. Reinforcing steel to be supported on the sub-base with 3" concrete blocks or plastic chairs."

In his infinite wisdom, the concrete contractor used #10 wire mesh as his reinforcing steel. And because it is so flimsy and cannot be supported on dobbies (concrete blocks), they left it laying on the sub-base. Lots of good it does there! He stated that as they poured the concrete, he "hooked the wire & lifted it into the center of the slab." I made him a gentleman's wager, that the wire was consistently in the bottom 1/4 of the slab, and would be found mostly on the bottom. He did not realize that once the workers begin to tamp & finish the concrete, the wire settles back down to the bottom. At best, a cross section of the wire in the slab looks like a "wave" throughout the slab.

Then he violated the building codes that specify the clearances from the reinforcing steel to earth and reinforcing steel to the surface of the concrete. The minimum clearance from earth to the BOTTOM SIDE of the reinforcing steel when the concrete is cast against earth is 3 inches! The minimum clearance of the TOP SIDE of the reinforcing steel to the surface of the concrete is 2 inches! So, had he used #4 sized (1/2" diameter) reinforcing steel, the slab would have had to be 6" thick! Since the #4 bars would be laid out in a checkerboard fashion, they cross over each other. This means that the steel is in some places 1" thick (1/2" + 1/2" = 1" thickness of steel at the intersections). 3" of concrete below the steel + 1" steel thickness + 2" of concrete above the steel = a 6" thick slab.

So, any concrete contractor who forms concrete that is to be poured against the earth (that includes the sub-base material) with 2x4 limber is in violation of the building codes (IBC, UBC, or CBC). And any client that contracts for a 4" thick slab is being cheated, as a 2x4 is actually only 3.5" high not 4"!

The stone veneer was mortared directly on top of the concrete slab. As the slab cracked, the cracks migrated through the stonework. The grout cracked & came loose, as did the stones.

Decks of this type of construction need to be built to protect the stonework from failure. The concrete slab should have had thickened edges and turn down footings around the perimeter. There should have been a "crack control" or "cleavage" membrane installed on top of the concrete slab. This membrane prevents cracks in the concrete from migrating through to the stone work - manifesting themselves on the surface.

If ground water or poor site drainage was present, a vapor barrier should have been placed beneath the concrete slab. The crack control membrane could have also been upgraded to a waterproof membrane, adding a layer of protection against efflorescence on the surface of the stone (from water beneath).

The final mistake, which actually caused the ground to start moving in the first place - was that the concrete contractor did not install any surface drainage. Instead, he talked the homeowner into sloping the decks back to the planters & allow the water to run off into the landscaping - saving the homeowner money on a drainage system. Not a good idea, when expansive soils are present. The water migrated back under the concrete slab through the finely crushed dolomite, where it soaked into the soils. Being expansive, the soils swelled, causing movement & cracking of the concrete slab, and cracking & separation of the stone veneer.

The turn-down footing at the edge of a concrete slab, is designed to strengthen the edges of a slab, prevent "slab curl" as it cures, and prevent water from migrating beneath the slab. Surface drainage should always be installed to direct water off of the decks. If the water is being directed to the side of the deck, then a trench drain or french drain needs to be installed to redirect the water away from the sub-base.

Since he failed to inquire or follow the soils report recommendations and relied on his inferior construction practices (e.g. wire mesh, hooking the wire mesh, 3.5" forms), he will bear ALL OF the expenses of jack-hammering & hauling away the current decks, excavating the site 30+ inches, installing a drainage system, importing the proper base rock, properly re-pouring the concrete decks, and reinstalling the stone veneer.

Again, having (and using) the recommendations in a soils report would have saved this contractor a lot of time & money. Had he followed the recommendations and still experienced these same failures, he would not have been liable for their correction.

Do it right, or don't do it!

Paolo Benedetti - Aquatic Artist
"Creating water as art."™
Aquatic Technology Pool & Spa
©www.aquatictechnology.com

Swimming pool designer builder Paolo Benedetti discusses U-Tunes, Underwater swimming pool speakers Santa Barbara, Montecito, Santa Ynez

Internationally acclaimed swimming pool designer and builder Paolo Benedetti of Aquatic Technology Pool & Spa discusses U- Tunes! Under water swimming pool speakers & sound.

Ancient Technology

Socially there has been a marked increase in the desire to have one's personal music collection available anywhere one might be. While underwater music has always been available, the quality of the speakers had left something to be desired.

Early speaker designs were mechanical, and though these ancient designs are still available, they are prone to constant failure. They oftentimes also require the use of a proprietary niche (a speaker manufacturer supplied plastic or metal pocket that is cast into the pool wall to house the speaker fixture). This requirement trapped the owner into keeping these deficient design speakers, so when they fail nothing else will fit into the niche.

Additionally, the physical design of the speakers are hideous. They are bulbous and protrude from the pool wall, drawing attention to themselves. Add to that, the fact that they are only available in white or blue, not harmonious with every designer finish. Absolutely no thought went into the aesthetics of the speaker itself.

But, they are inexpensive, so these are what most designers and pool builder specify or install. Remember what my grandpa used to say (translated from Italian)? "Cheap isn't good and good isn't cheap" Basically, You get what you pay for! With underwater speakers, this could not be any truer!

Those antiquated designs contained metallic components that require electrical bonding, magnets that rust, parts that promoted galvanic corrosion, are not of a sealed design (the plastic bulb housing eventually cracks and leaks), or do not have the ability to handle the high wattage input from modern music systems (they are usually limited to 35 - 200 watts @ 8 ohms).

And the biggest complaint... their sound fidelity is rotten! Rule of thumb: "If they sound like crap out of the water, they will sound like a truck load of crap underwater!"

U-Tunes

With the decades of advancements in electronic technology, so has the technology of underwater speakers, as I call them "U-Tunes!"

Gone are the days of expensive and potentially corrosive stainless steel niches. Metallic components have been removed. The advent of piezo speaker technology has eliminated the need for moving parts.

The best underwater speakers utilize any readily available standard sized swimming pool light niche, making swapping out to another brand at a later date feasible. I personally specify the full sized American Products PVC light niche, as it reduces the potential for leaks where a threaded conduit would thread into a stainless steel niche. The niche is still required to be bonded to the pool's bonding grid, as it contains a bonding straps & a stainless steel mounting rim (the speaker retention screws tie into this stainless steel ring). And, if anyone ever removes the speaker & desires to place a light in it's place, it is already properly prepared for the conversion.

The modern speakers sit flat in the niche, protruding only 1/2-1" from the wall. Most are black in color, but a few manufacturer's offer custom epoxy painting to match the pool finish color.

The sound fidelity? It is remarkable. High quality speakers can handle upwards of 400 watts @ 8 ohms! Be sure that your speaker is protected by an isolation transformer! It'll keep the speaker from being over powered. Some manufacturers will even build custom configured systems.

How many speakers?

Most residential swimming pools will only require one speaker. Because water molecules are touching each other, sound travels better underwater than in the ambient air. Also, all of the background noise in the backyard is muffled when you are underwater. Most pools up to 800 square feet can get away with a single speaker.

Preference

Everyone always asks... so here is my personal preference: OCEANEARS SP-8 SONIC BULB SPEAKER (http://www.oceanears.com/2002spk2page.html). Yes, they are expensive, but you get what you pay for.

The customer service alone is worth the extra money. I have had customers blow out a Oceanears speaker & they sent a replacement transformer at no cost. When the customer blew it out a second time, they sent a more powerful replacement transformer at no charge! Even when they determined that the client was over powering the speaker, they took care of business! My kind of folks!

I have never used or specified anything except Oceanears Speakers. I even have one in my personal pool (and I paid full price for it too!). I have a dozen of them in use dating back 10+ years.

The only problem that we've ever had what that one client who over amp'd the transformer. That client has been told do it again & be prepared to open your wallet, WIDE!

U-Tunes - excellent for parties, daily exercise, or recreational swimming.

Paolo Benedetti - Aquatic Artist
"Creating water as art."™
Aquatic Technology Pool & Spa
©www.aquatictechnology.com