Negative Edge, Vanishing Edge, Infinity Edge Pool Weirs & Walls

Paolo Benedetti discusses Negative Edge, Vanishing Edge, Infinity Edge Pool Weirs & Walls, design and construction considerations and the realities of routine maintenance vs. construction defects.

The Weir - The point of spillover...
The "weir" is the actual crisp edge that the water spills over. The material and design details that comprise this edge are critical.

Ceramic tile is the least forgiving when installed as a weir. The greater the variance in the surface of the tile & grout joints, the more water will be required to flood the edge. This also requires that the installer be "dead on" with their installation. Water will ALWAYS sit level inside the pool. If the tile is not installed level, the water will be a dead give-away!

I prefer to use polished natural stone. Though our specifications call for +/- 1/32" (a total of a 1/16" difference between highs & lows), natural stone can be further polished to ensure absolute perfection.

The grout joints will also contribute to variances in the weir elevations. Wider grout joints tend to have greater variances in their depressions. Additionally, they have a higher incidence of cracking.

NOTE: GROUT WILL CRACK - so, cracked grout, in and of itself is not to automatically be considered a construction defect!

Flowrates - low & slow is the goal!
The backside of vanishing edges are not supposed to be grand cascading waterfalls. Actually, the designer's goal is to flood the edge(s) using as low of a flowrate, and therefore as little energy, as possible.

This is not to say that they cannot be designed to be cascading waterfalls. However, if the owner desires a "waterfall" effect from the vanishing edge wall, then additional expenses and costs will need to be factored into the project.

A waterfall effect will require a material or weir that causes the water to break tension from the wall. It can be a simple change in the weir detail to create a large cascade effect. Or, an irregular material (e.g. ledger stone) can be installed on the outside face of the vanishing edge wall, to cause the water to splash free from the wall.

The cascading effect will require additional pumps & plumbing. Both effects will require a wider catch basin, as the splashing water will easily clear the width of a normally sized basin. Depending on the height of the vanishing edge wall, the width of this basin can be substantial. All of this translates to an additional project cost.

Choice of Veneers
What ever material is chosen to veneer the outside face of the vanishing edge wall, special construction techniques must be employed. Since the vanishing edge wall is in effect a giant dam, waterproofing is paramount. The waterproofing program should begin with the concrete itself and then include additional layers of protection as construction progresses. A competent
designer or builder will be intimately familiar with the options available.

The installation of the veneer material will require movement joints throughout the material. This means color matched caulking joints both vertically & horizontally through the material. Since this surface is repeatedly put through wet & dry and hot & cold cycles, the material must be able to expand & contract with these extremes. Failing to provide these joints will cause the material to crack or delaminate.

Efflorescence - French for "to flower out"
Whenever you have wet cement surfaces exposed to air, you will get efflorescence. It is a chemical reaction of the salts within the cement products hydrating & leeching towards the surface. The more the surface is subject to wetting & drying cycles, the greater the efflorescence to be expected.

Any cement product can contribute to efflorescence - concrete, mortar, thinset & grout. Even the labels on epoxy grouts contain a disclaimer about efflorescence.

There is no easy solution to preventing efflorescence. The key is to control the migration & penetration of water into & through the cement products. I say "through," because concrete contains microscopic capillaries through which water can migrate. There are chemicals and processes to control the water migration and saturation. The specifications just need to be defined and included in the project specifications - and, yes, they do add to the cost.

So, the presence of efflorescence is not a construction defect. It might indicate that the designer or builder did not include a waterproofing & migration control program (which you probably did not pay for either). This will result in the unsightly development of efflorescence and reoccurring maintenance expenses to remove it.

The caulking joints will also require periodic removal and replacement. The frequency of the maintenance of these joints will depend on the wall's exposure to the sun, temperature extremes, proper installation & joint preparation and the veneer materials. Materials with a high expansion index will place greater stress upon the caulking (mastic).

If you hire a knowledgeable designer & specifier, they can discuss the additional costs, help you weigh the maintenance and cleaning costs and the negative long terms costs and ramifications of not taking these simple precautions.


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

Build Your Own Vanishing Edge Pool ?

Infinity edge, negative edge, vanishing edge and knife edge pools should only be designed and built by reputable watershape designers, aquatic consultants or experienced contractors. Paolo Benedetti discusses WHY "building your own" pool is a foolish mistake...

Don't be penny wise and pound foolish!

Knowledge and Training
Pool builders who specialize in these complex "water in transit" designs usually have a few hundred hours of training in the intricacies of constructing these pools. Most have been building pools for years, prior to attempting their first water in transit design. And when most build their first one, they usually hire someone with more experienced to consult or assist them.

Why? Because even they realize that there is a really big DOWN SIDE, if things go wrong.

So why in the world would a homeowner even attempt to build one of these complex pools on their own?

Free advice on the Internet
There are countless websites, that purport to assist homeowners in building their own pools. Homeowners post questions, based upon their limited knowledge and ability to describe issues, and countless other nimrods give their free opinions.
When a sub-contractor asks for directions & the homeowner does not know the answer, what are they going to do? Post a question on the internet & select the first answer posted?
When things go wrong, who is going to assume the blame and correct the resulting problems?
Are they going to sue the guy who gave the free advice?

Hillsides & Slopes
Since most of these pools are constructed on hillsides to take advantage of the resulting views, there are a myriad of intricacies that MUST be adhered to to keep the pool on the hillside! If you are not intimately familiar with setbacks, deepened foundations, drilled caissons, step foundations or micro-piles, now is not the time to learn. A mistake here can result in a structural catastrophe.

This is also not the time to avoid spending money on a soils engineer. Since soils conditions can vary significantly on a single property, it is important to know what you're dealing with BEFORE you even dig the hole.

Site drainage is critical, as is the discharge of any accumulated rainfall. Undermining the slope below the pool can cause major issues.

Structural engineering needs to be specific for your project. What that means, is that the structural engineer has reviewed the slope topography and soils reports, and has prescribed the proper foundation design required for the issues unique to your project and site conditions. Oftentimes, they can actually provide generic pre-designed plans from their design library.

It is best to leave these decisions to those who specialize in these complex issues?

Sub-Contractors are not doing you any favors
The same goes for the pool construction industry's collection of sub-contractors. There is a reason that they are sub-contractors...
And their opinions are limited to what they have seen or done, right or wrong!
The more expensive sub-contractors are expensive for a reason - they usually do things correctly. But DIY'ers are not usually seeking the best... they are almost always seeking the cheapest!

And, human nature being what it is, sub-contractors are not always going to do what is proper, which is oftentimes a more difficult and costly method of doing something. They will take the path of least resistance - the easy way out. And is the property owner going to know any different?

Who's going to tell the homeowner that the following cannot be used to build an in ground pool?
non-site specific structural engineering (generic engineering without regards to the soil conditions)
wire mesh inside freestanding walls
drywall forms
flex pipe
shotcrete/gunite rebound & trimmings thrown into the benches, stairs and floor
insufficient strength shotcrete/gunite
sand lenses in the structure
epoxy coated reinforcing steel (in most instances)
brick as reinforcement supports
wire mesh on the ground of concrete flatwork
and hundreds of other potential mistakes that are made on "normal" pools

If the sub-contractors follow directions and do as they are directed by the "General Contractor" (Owner-Builder), then the Owner-Builder assumes the ultimate responsibility for the defects. They will have to show that the sub-contractor was grossly negligent in their work... but if the Owner-Builder does not possess the knowledge of what is right or wrong, then how are they going to know what was sub-standard??

Accountability
When a property owner acts as their own general contractor, the law assumes that they possess the knowledge required to supervise the construction and maintain the quality. I know, just ask the sub-contractor to do it the way they always do it (which is usually the wrong way)?!

So when the compacted soil settles...
The pool cracks...
The uphill slope shifts the decks & cracks the tiles and copings...
Termites eat the flex piping...
The concrete decks crack, because they put wire on the bottom...
The upper pool back siphons into the lower catch basin & floods the property below...
The mud slides into the downhill neighbors living room...
A neighbor child drowns because the gates swing the wrong direction or the latch is too low...
The family dog is electrocuted due to incorrect bonding...
The tile delaminates from the vanishing edge wall...
The decks heave from expansive soils...
The pool pump makes a lot of noise and cavitates...
The edge does not flood correctly...
The catch basin does not catch the water going over the vanishing edge...
The catch basin does not hold enough water and is sucked dry when the system comes on...
Dirt and debris blow back into the pool, when the vanishing edge pump turns on...
The spa jets do not siphon any air...
After cleaning the pump baskets, they do not prime...
The auto-fill device in on the upper pool...
Who is performing the hydraulic design, sizing the pipes and selecting the proper pumps...
Who is ensuring that the line velocities and feet per second of flow is acceptable...
Who is ensuring that the drains and properly spaced and that their covers meet the acceptable flow rates...
Who's specifying the waterproofing and ensuring that it is being installed in the mandatory places...

Who is responsible??? The homeowner is!!

Warranty or Lack Thereof...
The warranty for the structure is the responsibility of the General Contractor (in this case the Owner-Builder). So if the pool cracks, shifts, settles or sustains some other major defect... then the financial responsibility for making the repairs falls upon the Owner-Builder.

Correcting the Problems
Most problems with vanishing edge pools are VERY EXPENSIVE to repair.
$20-30,000 to strip, waterproof and re-tile a catch basin...
$20-50,000 to tear out a pool...
$30,000 to re-plumb one, after the decks are installed...
$15,000 to strip the plaster, waterproof & re-plaster...
$10-15,000 to seal around leaking pipes, penetrations, and fixtures...
$10-70,000 to level the pool...
$40-50,000 to remove & replace a vanishing edge wall....
$30-60,000 to remove & enlarge a catch basin.

SO, go ahead and paint your own house, but...


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

Baptismal Font - Architectural Masterpiece

Paolo Benedetti, the principal of the aquatic consulting and watershape design firm of Aquatic Technology Pool and Spa, proudly reveals another architectural masterpiece... the baptismal font for Saint Benedict's Roman Catholic Church.

Desperate Need of Repair
Though the original font was only 10 years old, shoddy workmanship by the original builder had cause significant damage to the surrounding floors. Though an initial attempt was made to waterproof the font, it was haphazard at best. Water was seeping up through the surrounding floors, causing a slippery and dangerous condition. As a result the, the font was drained and left empty.

Lack of Thought in the Design
The architect's original design lacked any thought into the architecture of the building, the space to be occupied, the acoustics or the practicality of actually using the font. Situated in the entry foyer of the Church, the font is the focal point on upon entering the building.

The original font had a three foot diameter aluminum bowl with a spillway that spilled water from a height of four feet into the lower pool. The sound of the falling water was amplified by the stucco foyer walls and it echoed through the Church. The annoying background noise urged parishioners to use the restrooms during mass. The diameter of the bowl was so small, that infant baptisms could not be performed, as the Priest, Parents and God-Parents could not fit into the space around the aluminum bowl. And, anyone who has ever worked around chlorinated water will tell you... chlorine eats aluminum! The upper bowl quickly developed leaks and became a myriad of assorted patches and repairs.

Access to the lower font's pool was always cumbersome and awkward, as it lacked an external step, hand railings and the internal steps varied in height by over two inches.

The New Design
Paolo was given carte blanche with new design. He proposed a much larger upper bowl, of a cubic design, better fitting with the building's rectilinear lines and mission architecture. The larger bowl would allow larger crowds to access the font at the beginning and end of mass. The height was established to provide access to the wheelchair bound that desired to bless themselves upon entry to the Church. The larger size would also allow infants to actually be baptized in their own parish Church! To assist with infant baptisms, the curbing of the upper cube was designed to be one foot wide, so that infants could actually be laid upon the rim if necessary.

The green slate that lined the inside & outside of the lower pool would be stripped. The ineffective waterproofing and loose mortar bed would be jackhammered off of the walls and floor. The upper and lower fonts would be finished with a custom gradient blend of Italian glass tile mosaics from Bisazza Mosaicos, Vicenza, Italy.

The hand railing from the adjacent stairs would be relocated into the top of the lower pool wall, so that it could provide assistance to both the users of the font and the external stairs. The internal steps of the font would be adjusted, so that they would be of equal height. Additionally, the singular drain was modified into two balanced drains and a vacuum port for maintenance was added. Exterior floor drains were relocated to allow for the installation of the access steps and the upper font cube.

The spillway was redesigned to function as a "wet wall" off of the corner of the cube. Being narrower on the inside & wider on the outside, the spillway's design will create the optical illusion that the water is not level on the top of the spillway.

A bronze statue of the ascending Christ that the Church had in an outer entry, was to be relocated to a commanding position atop the cube. The natural lighting of the overhead skylights would shine upon this space during the day. Overhead lighting was modified to highlight the statue and to accent the shadow lines of this dramatic art piece.

Theology of the Design
Though significant thought went into the redesign of the physical attributes of the reconstructed font, the real importance of the design is found in the use of colors, materials and their placement:

The bronze statue of the ascending Christ occupies a commanding position atop the upper font, gazing through the skylight towards heaven above.
A gradient blend of glass tile mosaicos originates with a blend of blacks & grays and transforms to a blend of yellows - baptism in Christ's name is leaving one's sinful past behind (blacks/grays) and signifies the dawn of a new life (sunrise/yellows).
The upper bowl (cube) is a blend of whites and opalescent pearls... infants that are baptized here are free of mortal sin (purity/white).
A smattering of 24 karat gold leaf mosaic tiles spill from the statue of the ascending Christ, over the spill way & cascade onto the floor of the lower font.... Christ is the source of our everlasting life.
The entry step contains a few yellow tiles... there is a little good in everyone, no matter how evil they may be.
A singular gold leaf mosaic tile is on the yellow exit step... Christ will forever be with those who are baptized & walk in his name.
The shadows from the hands of the ascending Christ touch both the black entry step and the yellow exit step... Christ will guide those baptized in his name through life.


(CLICK ON THE IMAGES TO SEE A LARGER VIEW)



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