Monday, October 27, 2014

Waterproofing and drainage - retaining walls and basements

Providing drainage alone behind retaining walls and against basement walls is not sufficient to prevent water migration through the wall.

Different Purposes

Drainage and waterproofing behind walls serve two distinct purposes.  Drainage is installed to transport ground water away from the structure.  Removing the water reduces the hydrostatic surcharge (weight of wet soil on the structure) and helps the waterproofing resist water intrusion.

Given infinite time, water will eventually seep through any waterproofing system.  Reducing the water in the soil adjacent to the wall, increases the waterproofing system's chances for success.

A waterproofing membrane is installed on the concrete, to protect it from water that migrates through the drainage system.  The waterproofing system also prevents water from seeping into and through the wall.  

Water passing through a wall can cause a myriad of issues: corroded reinforcing steel, mold and mildew in the basement, dampness and cold, dry rot, corroded nails and fasteners, electrical shorts, efflorescence, decay and discoloration of surface finishes.  As reinforcing steel corrodes it expands.  The steel's expansion can cause the concrete to crack - allowing even more water to enter.

Drainage Systems

Drainage systems should consist of a crush proof perforated pipe, wrapped in filter fabric.  The pipe should be installed with the holes DOWN.  As the rising water level enters the perforations, it will flow away in the pipe (incorrectly placing the holes up, forces the water  level to rise to the height of the holes, before it can flow away).  The filter fabric around the pipe, prevents it from filling with dirt, sediment and fines from the gravel.

Though inexpensive and readily available, black corrugated drain pipe is subject to collapse and filling with sediment.  It should not be used and is frequently prohibited by structural engineers and geo-technical engineers.

Vertical drainage behind the wall can be provided by crushed gravel or drainage mats.  Drainage mats provide time and labor savings.  They should be installed with the fabric side towards the soil.  Drainage mats also provide another impermeable layer of protection behind the fabric layer.

Click on image to see the lack of waterproofing and drainage
Waterproofing (aka: damp proofing)

For a basement redundant layers of protection are warranted.  These would entail an integral waterproofing agent mixed right into the concrete and an external membrane system.
Basement walls lacking waterproofing membrane (click image to enlarge)
There are a host of choices available to choose from, when selecting a surface applied membrane system.  There are spray on, roll on, peel and stick and panel systems.  What ever system is chosen, it must no have seams that allow the passage of water.  They should also extend below the perforated drain pipe and to the bottom of the structure.

Perimeter drainage around the foundation should be installed similar to that behind a retaining wall.  However, provisions will need to be incorporated for a sump pump to discharge any collected ground water, as the basement drainage system is usually below grade.

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

Friday, October 24, 2014

Floor tile crack control waterproof membrane - Proper Application

To achieve the full benefit of a floor tile waterproofing and crack control membrane, it must be installed in adherence with the manufacturer's instructions.


The substrate needs to be clean and free of foreign matter: dirt, oil, grease, dust, moisture.  These create a layer between the substrate and the membrane that prevent complete adhesion.
Improperly applied TEC Hydraflex Membrane - click on image to enlarge


For the membrane to be effective, it must be installed to the thickness specified by the manufacturer.  To achieve these thicknesses oftentimes requires 3 to 4 coats.  One layer is usually insufficient.

Good rule of thumb: If the substrate can be seen through the membrane, the membrane is too thin.  Better yet, buy a tester and measure the membrane thickness to verify the minimum thickness has been achieved.


The membrane must be cleaned of dirt, dust and debris that collects on top of it.  Thinsets and mortars will not adhere to a dirty membrane.


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

Wednesday, October 15, 2014

APSP NPC ANSI ICC ANSI/APSP-12 Pool Plaster Standard

ANSI/APSP-12 Swimming Pool Plaster Workmanship Standards

How bad can it get and still be defensible?

On July 28, 2014, the APSP and the NPC announced a “joint” committee to write a new plaster workmanship standard, under the guise of APSP/ANSI-12.  The alignment of APSP with ANSI, would in effect cause the resulting standards to become “statute” in many regions of the country.  Through ANSI's affiliation with the ICC (International Code Counsel, who ironically published the International Building Code, which has been adopted across the US), this may just become law in your state. 

You can see where this is going.  It is a end around run on consumer rights, forcing them to settle with inferior workmanship, just because it meets the industry's own minimum acceptable level.  

In other words, "how bad can it get and still be defensible?" 

Their proposals for this standard include defining acceptable "deviations" and explanations as to why pool plaster cannot achieve the levels of performance delivered by other plaster trades.  These deviations will be governed by "accepted trade practices" and not the BEST AVAILABLE PRACTICES.  Again, locate and identify the lowest common level of performance and make that acceptable.

Fox in the Hen House

Trade associations writing their own workmanship standards is self-serving and against the general interest of the American public.  Even if a standard is written with the absolute lack of personal biases and interests, the end result will still be a self-serving document.   

This is what I take offense with… putting the fox in charge of the hen house.

The pool builders association will continue to refuse to hold their members responsible for delivering properly constructed and prepared shells, watertight, trimmed and prepared to precise tolerances.  Due to the generous workmanship tolerances provided pool builders, plasters are relegated to dealing with the issues and variables you described.  Almost every one you describe is the result of a poorly constructed shell.

There is absolutely no reason why a plaster pool finish cannot be delivered with a smooth, even finish that is color consistent from batch to batch.  Many of these issues are a direct result of the human tendency to avoid conflict or extra effort:

·      Plastering in adverse conditions (e.g. high winds, extreme heat/cold)

·      Staffing difficulties (e.g. insufficient time allotted, inadequate staffing levels, poor training)

·      Improperly prepared shells (e.g. leaking, seeping, voids, dry, hot)

·      Shells with poor tolerances (e.g. wavy surfaces, penetrations trimmed at incorrect elevations, improper radii)

·      Poor quality control measures (e.g. failure to measure/weigh batch contents or water)

·      Failing to perform pre-site visits, preparations or inspections

·      Refusal to hold builders responsible for making shell corrections

No one wants to tell the pool owner that their pool will not be plastered due to any issue.  Nor is it cost effective to have to leave and return.  Most pools should never be plastered in their state of readiness, as delivered to a plaster company.  Yet the plaster company wants to satisfy their customer - not the pool owner, but the pool builder who brings them steady business. 

I find the lack of a quantifiable maximum water to cement ratio for a cementitious finish audacious.  Pre-packaged materials should contain maximum allowances for water or approved admixes.  Yet the loose NPC standards allow the crews to add water to extend its workability due to weather, short staffing or mere laziness or refusal to measure the water (they just add water from a hose until it looks good ).

Too much water is bad

It has been scientifically proven that excess water in cementitious products compromises it’s strength, causes discolorations, increases porosity, encourages shrinkage and promotes check cracking.  The NPC should not be allowing carte blanche with the water to cement ratio and then attempt to justify the errant results. 

To advocate the unfettered use of water by untrained personnel is irresponsible, especially when there are inexpensive and viable alternatives and techniques.  Instead, the NPC should be promoting improved quality through the use of various admixes – additional water, not being one of them.  Set accelerators, retarders and plasticizers should be the norm, instead of the exception.  The workability and plasticity of the product would improve, as would the durability and quality.  Archaic practices, such as the addition of calcium chloride and the re-tempering of finishes would no longer be required or acceptable. 

Acceptable Alternatives

These advanced methodologies and admix practices should be advocated and promoted.  Calcium chloride alternatives and set timing admixes are utilized in every other plaster trade, in compliance with the requirements of the pigment manufacturers.  Steel troweled plaster finishes are applied multi-stories in the air, delivered by the bucket, on scaffolding, in the hot sun and in windy conditions.  Their substrates are wavy and irregular.  These trades even lack the luxury of flood curing their finishes.  Yet the results are often far superior to the results seen in the pool plaster industry – even without remedial work. 

Cement chemistry is nothing new.  It dates back centuries to the Roman’s use of volcanic ash as pozzolans and animal fats and milks as plasticizers.  Yet, the swimming pool industry is always the last to embrace decades old and proven methodologies and technologies that are utilized in other related construction trades.  When these practices are “discovered” by our industry, their revelations appear as a sudden rapture (recent case in point – penetrating sodium silicate curing compounds for shotcrete & concrete).

Virtually flawless pool plaster finishes are achievable.  I consider myself very lucky to have plaster sub-contractors who understand the idiosyncrasies of their trade.  I take pride in delivering a high tolerance and quality watertight shell upon which they can ply their trade.  Pre-site inspections with my sub-contractors identify concerns that can be addressed prior to plaster day (pressure washing & surface prep, local water quality, staffing requirements, weather forecasts, access, etc.). 

My favorite sub-contractor (Adams Pool Specialties) brings their own water supply, which is measured as it is metered into the batch.  This is not rocket science – just an expressed concern with craftsmanship.  The end results are that my clients receive a virtually flawless hand troweled plaster finish, free of the issues that plague the industry.

Through this new joint APSP/ANSI-12 standards committee, the NPC has the opportunity to establish shell tolerances and standards, which will allow their members to execute higher quality finishes.  NPC members should no longer accept shells that fail to meet defensible workmanship standards and design tolerances, which affect their end product.  The American public needs to be given cosmetically acceptable standards, not minimums that are barely acceptable.  The need to defend the resultant questionable workmanship and cosmetic blemishes will become a thing of the past.

Let's see who takes the high road...

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