Cracked Swimming Pool Los Gatos Mountains

Owner Knows Best...  NOT!

This was one of those cases, where the owner's wife was a "bossy know-it-all."  She had the where-with-all to hire me as a consultant, yet did not want to hear the advice that I was being paid to provide.

Solution to everything

Just because she was married to a rich and wealthy silicon valley executive, she had a solution to everything.  The pool was originally built on top of a hill, without the benefit of any soils reports (that she could remember).

Her memory was conveniently foggy about the engineering and construction of the pool.  However, she remembered the exact vendor that replacement coping and deck stones could be procured from.  She could not even recall the pool builder, yet knew the gunite and plaster sub-contractors.  Something just "didn't seem right" about her selective memory.  I was already beginning to speculate that this was a very manipulative woman.

Poor planning and execution

By her own admissions, the pool was built atop fill from the excavation of the mansion.  Since then, the fill obviously began sliding down the hill.  

The hill was visibly creeping and slipping, and the pool was moving with it.   Yet, she could not remember if the hillside benefited from being properly compacted under an engineer's supervision.

 (Click on any picture to enlarge it)

Homebrew solution

Without the benefit of a geologist or structural engineer, she figured that if she threw enough of her husband's money at the problem, it would go away.  She concocted a scheme to build a 12 foot tall retaining wall below the pool, to stabilize the hill and pool.  Yet, she was building the wall with geo-blocks without any deepened foundation.  

The surcharges and loads upon the new wall were completely unknown.  And no concern was given to the setbacks from the slope.

Humpty Dumpty

Her pool was what I call a "Humpty Dumpty Pool"- it had fallen, cracked into pieces, and all of the king's horses and all of the king's men could not put it back together again.

Yet, the she had already spoken to a local "epoxy injector" who was willing to inject the cracks.  He was then going to install glass tile mosaics throughout the interior of the pool.

She wanted me to provide a bid for the same scope of work.  I refused.  The pool had structural cracks, the pool was losing water, was out of level and it was built atop questionable soil conditions.

Patient refuses the doctors advice

Even when provided all of the facts, the "patient" (owner) refused to admit that the pool was terminal.  Her retaining wall "fix" was not approved by any engineer to stabilize the hillside, and work was already underway... all without permits.

You cannot save people from themselves

The owner's wife kept pressuring me to concur with her solutions.  I told her that the facts were the facts.  Regardless what the "epoxy charlatan" was advising her, the pool was beyond repair.  Not what she wanted to hear, but the truth.

I decided that regardless of what I told her, she would go off and do what she wanted.  She really hired me in an attempt to validate her erroneous foregone conclusions.  However, I refused to bow to her pressure.

After the remodel project, as the pool continued to move, the cracks returned, new tile mosaics popped loose, her retaining wall began to fail and the vessel began to leak - she would have returned.  Only this time it would be with a lawsuit for providing faulty advice.

Walking away from such clients is the smartest thing you can do.   These people are used to always "having their way."  And when their schemes do not work out, they're always going to seek someone else to blame.

Not me.  Not this time.

At least the doctor got paid.  

And I'll be ready to provide expert witness or inspection services to anyone involved in future litigation over this pool's structural failure.

Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: info@aquatictechnology.com or 408-776-8220. 
 Visit his website at: www.aquatictechnology.com. 
All Contents © Aquatic Technology Pool & Spa, 2013. 
All rights reserved.

Napa Swimming Pool Design Epoxy Injection

Epoxy injection of cracks in concrete is like putting a bandaid over skin cancer.... you no longer see it, but it is still there.

It's all great in theory, BUT...

The theory behind epoxy injection of concrete, is to seal cracks and to restore the integrity of the concrete (seal the crack).

Cracks are like people - they come in all shapes and sizes.  Unfortunately, tight skinny cracks cannot be effectively sealed.  

Fat and wide open cracks are not good candidates for epoxy injection.  Why?  Because they indicate that there is a substantial structural issue.
 
Wheels falling off beforee the race even starts

If your brand new pool is full of cracks before it is even plastered - there is a PROBLEM!  Do not listen to your pool contractor, something is WRONG.

The bottom line is that swimming pools should not crack.  PERIOD.  They are designed to hold water.  How can they do that when they are full of cracks?

Practical experience tells a different story
 
Personally, I have NEVER seen an epoxy injection job that sealed the cracks all of the way through a shell.  

I have cored a number of pools that were previously epoxy injected, and in none of the cases did the epoxy get any deeper than an inch or two.  

It did absolutely nothing to seal the cracks on the back of the structure to prevent ground water from entering the concrete and attacking the reinforcing steel.  

The purpose of complete encapsulation and proper coverage over the steel, is to protect it from corrosion.

Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: info@aquatictechnology.com or 408-776-8220. Visit his website at: www.aquatictechnology.com. All Contents © Aquatic Technology Pool & Spa, 2013. 
All rights reserved.

Wine Country Swimming Pool Shotcrete Shrinkage Cracks

I was recently hired by a homeowner in California's Wine Country, to address some shrinkage cracks in their new shotcrete swimming pool.

The term "shotcrete" can refer to either wet or dry mix pneumatically placed concrete.

Possible Causes

1.  Thickened shell without additional steel.  A single curtain of steel is inadequate in concrete that is 12 inches (or more) thick.  There is not enough steel to control shrinkage that naturally occurs when concrete cures.  This is why you need a structural engineer to design plans based upon the site's soil conditions.

2.  Excess moisture.  If the pump operator, ready-mix driver or nozzleman (depending upon wet or dry mix) added too much water, the resulting concrete will not have the proper water/cement (W/C) ratio.  Additionally, the structure will be weaker.  Remember, in concrete less water is better.

3.  Improper curing practices.  ACI 318 outlines the acceptable methods of curing concrete (shotcrete included).  Physical membrane (plastic), fabric that is kept wet (carpets, burlap, etc), wet curing (keeping wet with soaking or flooding), curing compounds.  
Lets face it, carpets and plastic are a hassle.  Plastic blows around & what do you do with hundreds of yards of wet carpeting?  
Most wet curing is done poorly - the structure is allowed to dry out between the wetting cycles.  
Flood curing will ensure that the structure remains wet.  But it does not address the horizontal surfaces (tops of beams, cover boxes with drains, etc).  
Only using curing compounds will ensure that EVERY SQUARE INCH of the concrete is protected and ensured of a controlled release of the water.  And after all, it is the practice specified and employed by most highway transportation departments and the DOT for concrete highways, sidewalks, structures and bridges.

4.  Failure to saturate the sub-grade or rock pack prior to the shotcrete placement.  The underlying materials will suck water from the shotcrete from the backside.  On past projects I've had engineers specify that visqueen be placed on the grade (like is required under slab foundations).  This can also provide the structure with some protection from reverse ground water migration.

5.  "Bad concrete" - Really, these is no such thing as bad concrete, only poor mix designs.  Usually they are incorrect for the project or conditions, excessive transportation or waiting times (from initial mix to placement).  Wet concrete experiences "blooms." If it experiences it's second bloom prior to being placed, then you might as well send it back.  There are set retarders and additives that can control these times.  The mix design can be destroyed simply by the pump operator or truck driver adding more water.

6.  Weather conditions - excess heat or high winds can all cause shrinkage cracking by causing rapid evaporation of the water from the concrete surfaces.  Again, there are special additives that can be added to ready-mix concrete to assist in combating some of these conditions.

7.  A hard freeze - water turns to ice, ice expands, concrete cracks, enough said.  ACI 318 has specified parameters for the environmental conditions during and after the placement of concrete.  If it's too hot or going to be too cold, you better learn about and employ some protection.

8.  Shotcrete installed in horizontal lifts (like layers of a cake), instead of in one thickness from one end of the structure to the other, can result in a compromised shell.

9.  The shotcrete company "flashed" the interior of the pool at the end of their job and gave it a pretty broom finish.  
What they are really did, was clean out their hoses and hopper by spraying a watered down soupy mix all over the inside of the newly shot pool.  The best laid plans are destroyed by this weak and incompetent crust of waste material.  Tell them to bring or build a washout bin for this purpose.  When doing wet mix shotcrete, some ready mix companies will allow them to washout back into the truck.

10.  Incompetent shotcrete placement & finishing techniques. For example: trimmings, rebound and reworked material are placed back into the structure; trimmings and loose materials allowed to accumulate beneath steel; trimmings and rebound allowed to accumulate between layers; improper encapsulation of the steel.  Trimmed material from the floor of the spa it thrown by hand into benches, seats and stairs.

11.  Poor soil conditions - the pool may be experiencing movement cracks.  If the pool was constructed on fill, soil that could not bear the loads or even expansive soils, the pool may be experiencing movement cracks.  Add to this, an 18 inch thick structure with a single curtain of steel, and you have a potential problem.

12.  Excessive foot and shotcrete hose traffic.  This is more commonly seen in dry mix shotcrete (but it can happen in wet mix as well).  Excessive foot traffic or the dragging of the hoses around the floor, reworks the concrete.  This compromises the initial compaction and placement of the concrete and forces water to the surface.  The rapid evaporation of this surface water results in a weakened area of shotcrete.

Any one of these factors can cause shrinkage cracks.  Combining a couple of them will surely result in disaster.

Bottom line, there are many possible causes.  

Without proper structural engineering, construction specifications (mix designs, special inspections, quality assurance testing), builder supervision, documentation and photographs - there is no means to tell exactly what the cause was.

The only real issue is... the pool builder has an expensive mess on his hands. 

Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: info@aquatictechnology.com or 408-776-8220. Visit his website at: www.aquatictechnology.com. All Contents © Aquatic Technology Pool & Spa, 2013. 
 All rights reserved.

Woodside Atherton Swimming Pool Designs

It's Cracking BEFORE it's even finished...

Cracks - everywhere...

Recently a client hired me to inspect a brand new pool that they were in the process fo having built on their estate, on the Woodside - Atherton, CA border.

It seems that the shotcrete that was placed a few weeks ago had developed cracks all over.  The pool builder assured them that this was a normal occurrence and that there was nothing to be concerned about.

Many Possible Causes

There were many possible causes.

The gunite company could have used too much water in their mix design.  The rapidly evaporating water would have caused shrinkage cracks.

The pool may have been cured improperly, allowing the water in the concrete to depart too rapidly, causing shrinkage cracks.

The gunite could have been mishandled after placement (e.g. walked on), forcing water to the surface.  That accelerates the water loss and causes shrinkage cracks.

The gunite crews could have cleaned out their hopper, mixer and hoses by spraying that rubbish all over the inside of the pool & then "broom finishing it."

How bad is it?

After sounding the shell with a "tuning fork," it was determined that there were hollow pockets of concrete.

Only taking core samples of the concrete, directly over some of the cracks, would tell for sure.  If the cracks extended through the structure, then someone had a lot of work ahead of them.

That bad

It turned out that the cracks extended through the structure.  Since a swimming pool is supposed to be watertight, cracks are unacceptable.

Epoxy injection is equivalent to putting a band aid over skin cancer.  It only hides the problem.

The only solution was to demolish the affected areas and to replace the shotcrete.

You would not accept a cracked concrete foundation or bridge... so why would you accept a cracked pool?

Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: info@aquatictechnology.com or 408-776-8220. Visit his website at: www.aquatictechnology.com. All Contents © Aquatic Technology Pool & Spa, 2013. All rights reserved.