All pool plaster finishes should last 20 years or more. However, some last only 5 to 7 years, and some less than a year before the plaster surface deteriorates, discolors, and looks terrible.
Why the difference? Very often, plaster quality. As we have pointed out previously, studies on pool plaster and cement/concrete flatwork have shown that poor workmanship practices have the greatest effect on durability, deterioration and discolorations. Various studies also confirm that water chemistry plays only a minor role.
Fortunately, there are a lot of quality plasterers that understand the importance of proper plastering, and generally take an extra hour or two to properly plaster pools with good materials and good workmanship practices. Their pools usually last 20+ years.
However, there are some poor-quality plasterers that are in a hurry and use inferior and “short-cut” practices and/or materials to plaster quickly. Doing so allows them to underbid the quality plastering companies. Their pools usually last less than 5 years, and sometimes less than a year before the plaster problems begin. And when the plaster finish starts looking bad, they simply blame the water chemistry instead of their own sloppy workmanship. Sadly, they are enabled to do that by the NPC and APSP.
A “Pretend” Plastering Standard
A few years ago, the NPC and APSP got together to write an ANSI plaster standard. Unfortunately, they refused to mention and include important and critical workmanship requirements (well known by the cement and concrete industry) that would produce quality, durable, and discoloration-free plaster/cement finishes. No limits or standards at all!
Furthermore, the APSP/NPC standard doesn’t mention the defects, deteriorations, or discolorations that can result due to improper and inferior workmanship. That means there is no accountability for plasterers that do poor work. Sounds like a “protection” standard. Pool builders and State Contractor License Boards have little recourse to help pool owners.
What about Water Chemistry Standards?
On the other hand, APSP and NPC have very strict and narrow standards for pool water maintenance. Beyond that, their literature (incorrectly) suggests that if pool water is not maintained within their suggested water parameters, that plaster problems will result. No, in reality plaster studies show that slightly aggressive LSI water does not cause the defects or discolorations at issue.
The NPC and APSP should not be exaggerating and misusing the importance of proper water balance which leads to service techs and pool owners being incorrectly blamed for many different plaster problems.
Obviously, poor water chemical maintenance can result in uniform etching and/or scaling. Even some types of metal staining can be traced to chemical mismanagement. However, when plasterers attempt to associate spotting, streaking, mottling, discoloration of the paste, calcium nodules, spalling, etc. to water chemistry causes, you know there is no basis for that. They are factually known to be caused by improper materials, application or curing failures.
The Bottom Line
APSP and NPC should rewrite the ANSI Plaster standard and adopt applicable workmanship standards (similar to ACI and PCA standards) to promote durable and discoloration-free plaster finishes for pool owners. That would serve the industry much better and help prevent plaster problems occurring in the first place.
However, this ongoing travesty probably won’t change until the entire pool industry becomes informed of these issues, rejects the false claims that water balance is what causes the above plaster problems, and demands that the NPC and APSP make things right.
When a plaster finish develops discoloration or defects, the following questions should be asked.
What does adding too much water, or too much calcium chloride (hardening accelerator), or performing too much water troweling, or overly late and excessive hard troweling do to plaster finishes?
And wouldn’t “tenting” pools (to overcome harsh weather conditions) and taking an extra hour help to produce a higher-quality plaster finish?
Those are the important issues that are missing from the APSP/NPC/ANSI Plaster Standard.
The following links provide additional details regarding these issues.
Comments and questions are welcomed.
Here in New Zealand 2 brand of Plaser one from Australia and another from Florida have been causing concerns my research has revealed the products have been re mixed to remove the Lumps in the bags that have Hydrated.
Not good for the owners have seen plaster reloaded away in 3 to 6 years.
The success of any plaster is freshly made Plaster and fresh Cement.
I like hearing that there are good plaster companies out there, and that they do good work. I am glad that you have one in your area.
Great info Kim.
My plaster contractor will tent my pools if any threat of rain is present and also on hot days to prevent the plaster from drying too fast.
This is especially important on any polished finishes as the crew returns the following day to perform the polishing. It's the between time that the finish needs the protection. It's not a big deal to tent a pool especially when there 10-12 men on hand to help with the set up.
Too much calcium can definitely alter the finish and wetting and overworking the surface is not good. Sometimes you just have to leave it alone.