Swimming Pool - Minimum Concrete Strengths & Special Inspections

4,000 PSI Shotcrete - there ought to be a law...
aah, but there is and it is rarely adhered to or understood.

Code Requirements 

Variations of the International Building Code (IBC) have been adopted in every state of the US, except Minnesota.  The IBC has many sub-books, the most popular being the International: Residential Code (IRC), Mechanical Code, Plumbing Code, Electrical Code, and yes, Swimming Pool Code (ISPC).

No one code addresses everything one needs to comply with in order to build anything, whether it is a wood framed house, steel barn, concrete bridge or swimming pool.  Instead, one needs to comply with the various portions that apply to their project that are found in the different areas of various codes.

Concrete & Shotcrete Codes

The IRC contains sub-chapters on concrete construction and shotcrete.  Shotcrete (wet or dry mix methods of pneumatically applying concrete) is concrete construction.  The code recognizes this, so the shotcrete chapter specifies that the chapter on concrete shall also apply to shotcrete.

The concrete chapter specifies that the MINIMUM strength for the construction of any concrete structure is 3,000 PSI.  But, the chapter also directly references and incorporates ACI 318-96 (1996), which specifies that shotcrete shall be 4,000 PSI.

Further complicating matters, the chapter on shotcrete makes direct reference to and incorporates ACI 506R-90 (1990), which also specifies that shotcrete shall be 4,000 PSI.

So, merely by reference and inclusion in the IRC/IBC, the American Concrete Institute (ACI) has set the minimum building code standard for shotcrete construction at 4,000 PSI. 

Special Inspections & Testing

The IRC sub-chapter on shotcrete also requires special inspections of the following (not a totally inclusive list):
reinforcing steel
shotcrete process and placement
initial curing process
mix design
testing and sampling
28 day compression testing (laboratory)  

A special inspection, is not the regular city building official's inspection.  Rather it is a qualified inspector from an independent observation and testing firm.  The special inspector (sometimes called a deputy inspector) is required to stand and observe the entire shotcrete placement process.

They are also required to monitor the mix designs and obtain test panels for later compression testing.  This does not mean that the shotcrete company shoots material into a test cylinder.  Instead, they must build panels of a prescribed size and actually shoot the material just as if they were creating the structure.

Structural Engineers  

In an effort to "save" contractors the expense of special inspections and worse yet, the oversight of an independent inspector, some structural engineering firms specify only 2,500 PSI shotcrete.

The code requires that concrete specified over 2,500 PSI be subject to all of the above special inspections.  But, because the code specifically states that shotcrete shall be a minimum of 3,000 PSI, this maneuver is no longer valid.  Special inspections and testing can no longer be danced around - they are the law.  While not every state has included the specific shotcrete chapter in their adopted versions of the IRC, it becomes included through the inclusion of the ACI standards.

So, now if your structural engineer specifies only 3,000 PSI, they can still be in violation of the building code.  Because, through the reference of the ACI standards, the IBC/IRC (and the even more restrictive California Building Codes) now make 4,000 PSI shotcrete and special inspections THE STANDARD.


Paolo Benedetti 
Aquatic Artist, Construction Consultant & Expert Witness 
"Creating water as art."™ 
Aquatic Technology Pool and Spa 
©www.aquatictechnology.com

Expert Swimming Pool and Spa Advice from International Designer

The causes of most construction defects are directly attributed to one of 2 causes - failure to follow instructions, plans or project specifications and/or the lack of qualified supervision.
 
Failure to Follow Instructions

Most defects in construction projects are directly attributed to someone not taking the time to READ instructions.  Whether they be the product usage insert, manufacturer's installation manual or the engineer's plans and notes... failing to take the time to read AND understand the instructions results in errors.

Sometimes these errors can be huge - incorrect strength or diameter of steel, walls that are too thin, pipe diameters that are too small or electrical systems that are incorrect.  These types of errors can result in a project that may be structurally unstable or dangerous to swimmers.

When these instructions refer to another code or standard, it is the installers responsibility to seek out and understand those codes as well.   

In the plans if the structural engineer states, "Shotcrete must be installed in compliance with ACI 506R-05," then the installer must understand what those standards require.   

The structural engineer does not need to reprint the entire referenced standard in the plans.  Why?  Because anyone who installs shotcrete as a part of their business should already be aware of, possess a copy of, and be following the requirements of ACI 506.

If the instructions that are enclosed with electrical components are not read and adhered to, a potentially life threatening situation can be created.  The failure to properly bond metallic components can result in a fatal electrical shock.  Though most electrical components clearly state how they are to be installed, many will also refer to NEC 680 & 682.  Again, anyone who builds swimming pools or fountains should have a copy of these codes and be intimately familiar with them.

The Lack of Qualified Supervision

Note the word "qualified?"  Just because a project has on-site supervision does not mean that the supervision is worth anything.  The supervisor may just be directing the progress and may "no nuthin' 'bout da details uf da wurk."  Therein lies the problem... the blind leading the blind.

The person who supervises the work of others, needs to know how that work is to be performed.  The person supervising the design, planning and construction needs to be familiar with:
structural engineering
soils
excavation 
building forms
hydraulics
plumbing 
electrical
reinforcing steel
shotcrete (wet or dry mix methods)  
tile
masonry
plaster
concrete
mechanical (venting)
fuels (approved piping, venting, shut-offs)
automation and controls 

This is not to say that they need to be a licensed expert in each of these fields.  But, it is saying that they need to know enough about each topic to question what others are telling them is right.  Anyone can make a mistake, even experts that the contractor may hire.  

The contractor needs to understand that pools with diving boards must comply with various floor contour and shape requirements, and which diving boards can be safely used in each.  They must ensure that the project design and engineering complies with these codes and minimum dimensional shapes.

The swimming pool contractor needs to be able to recognize differential soils or buried trash during an excavation.  They need to be smart enough to have the structural and soils engineers weigh in on the discovery.  It may mean nothing or it may be a big deal - but they need to let the experts decide which!

The contractor needs to understand the basics of hydraulics and the Virginia Braeme-Baker Safety Act, in order to deliver a swimming pool that is safe from entrapment hazards, unwarranted restrictions, high energy consumption and cavitation.  The need to ensure that the suction point sumps are the correct size, are compatible with the flow rate ratings of the drain covers and if sumps are field fabricated, that they meet the requirements of the VGBSA.

The supervisor on the project needs to know what each of the sub-trades are required to do.  Whether it is the electrician, plumber, mechanical, masonry or concrete sub-contractor - they need to know the codes and standards that apply to each.  And they have a duty to ensure that these codes are followed and complied with - even if the local inspectors do not enforce the codes.

Because when the client has any doubts about the project, an expert will come in and dissect the project.  Each component of the pool that is found non-compliant may be required to be corrected.  Tearing out completed work to repair underlying defects can quickly consume any project profits.

And anyone in construction will agree... it is cheaper to do it right the first time!

Take the time to READ and UNDERSTAND the plans and installation instructions.  

Employ QUALIFIED project supervisors or go get educated... there are some excellent programs on swimming pool construction available.  The $3,000 spent on one of these programs, will save you much more than that, if an expert is ever hired to evaluate one of your projects.


Paolo Benedetti 
Aquatic Artist, Consultant & Construction Defect Expert Witness 
"Creating water as art."™ 
Aquatic Technology Pool and Spa 
©www.aquatictechnology.com