Ten Guidelines for Quality Pool Plaster

onBalance

TFP Expert
LifeTime Supporter
In The Industry
Jul 25, 2011
974
Utah
There are proper steps to follow for the making of durable pool plaster. There are also improper practices that can lead to early deterioration or discoloration. Following is a ten-point checklist that will help achieve a lasting and discoloration free plaster.

1. The best cement/aggregate ratio is about one part cement to 1.5-1.75 parts aggregate (marble sand). If the plaster is too rich (cement-heavy), it tends to shrink and crack. If it's too lean (more sand), it will be less durable and potentially unworkable. Note: Always select high-quality and appropriate-grade cement and aggregate.

2. When mixing plaster, a thick mix is best. Shoot for a water/cement ratio of .48 or less. Both the American Concrete Institute (ACI) and the Portland Cement Association (PCA) maintain that lower water/cement ratios produce better-quality cement that can withstand occasional exposure to mild acids.

Lower water/cement ratios boost density while reducing permeability, porosity, shrinkage (craze cracking) and water movement within the cement product. Higher water/cement ratios, by contrast, cause excess shrinkage and cracking, and fail to offer adequate protection or long-term durability against the effects of water and the environment.

3. A plaster mix should be mixed thoroughly, but also not too long. It is recommended that if the plaster has been mixed for more than 90 minutes, the plaster mix should be discarded.

4. Plaster should contain as little calcium chloride set-accelerant as possible and never more than 2 percent to the amount of white cement. (Colored plaster, of course, should not contain any calcium chloride as it will lighten the color and become blotchy.) According to the PCA and other testing facilities, too much calcium chloride increases gray mottling discoloration and cement shrinkage. Several alternatives to calcium chloride that do not exhibit these characteristics are now available. The plastering of typical size residential pools shouldn't be completed in less than 4.0 hours.

5. Never add water to plaster surfaces while troweling. Both the ACI and PCA have found that this may increase porosity, shrinkage, and variable (white or light) discoloration. A little water to lubricate the trowel, however, likely will not harm the plaster surface.

Still, you never want to work, or force, additional water into the plaster surface when troweling. Doing so can weaken the surface and may accelerate deterioration and caused spotting or streaking discoloration. Dark colored plaster is even more susceptible to white spotting and streaking discoloration from too much water troweling.

6. Well-timed hard troweling can help produce a nice, dense plaster finish. But if the plaster becomes too hard before a smooth surface is achieved, continued hard troweling will often result in dark gray discoloration and spotting, especially when calcium chloride is also used.

7. Plastering in extreme weather conditions can lead to quality and durability problems. Industry groups specifically warn against using cement-based products in temperatures considered too hot or cold. The plastering process should take at least 4 hours to complete for typical residential pools.

One solution is "tenting" the pool, which protects the plaster surface (and the plasterers!) from the elements. In extreme dry heat, tenting the pool, and perhaps even directing air from an evaporative cooler beneath the tent, will help the plaster retain its moisture, and properly cure and harden without cracking.

8. Do not fill the pool with water too soon. Though conditions vary, water usually should not be added for at least six hours after the pool has been plastered and finished. This should be enough time for the plaster to harden properly before being submerged in water. It needs to be understood that the bottom or "bowl" area of the pool is the last and final section of the pool to be finished, and the walls are finished first. The bottom area of the pool needs to hardened before being submerged in water, whereas the plaster walls don't see water until many hours later, which is the way it should be. Even balanced tap water can dissolve certain plaster components if the surface has not adequately hardened. The end result is often greater porosity and early deterioration, which may take a few months to show up as a different shade of color on the bottom of the pool.

9. Soft or aggressive fill water can also deteriorate new plaster surfaces; and the effect is uniform. Ensure tap or fill water is balanced with sufficient TA and CH before using to fill the pool. Other new plaster problems such as drips, splotches, spotting, trowel marks, and hand- and footprints are the result of localized finishing errors.

Surfaces may be further damaged by aggressive (acidic) startup techniques, which can cause additional uniform surface loss. By contrast, baking soda startups can neutralize aggressive fill water while promoting a superior plaster surface.

10. Once the pool is filled, balance the water (and keep it balanced). Balanced water helps help preserve the plaster. Aggressive water causes uniform etching, while over-saturated water scales plaster. The Saturation Index is a good guide to prevent scaling or etching, water should have a saturation index value in the range of -0.5 to +0.5.

EDIT: It is acknowledged that adhering to quality standards will lengthen the time it takes to plaster pools. Generally, a plaster crew should spend at least four hours or more to plaster a typical residential pool. If it takes only three hours, that might mean it was done too fast and may result in plaster problems appearing later. During cold temperatures, it may take six hours or more to do the right job.

We emphasize that quality over quantity must prevail to ensure the rights of homeowners to quality products, and a responsibility to builders to ensure a commitment to quality of their projects.

With reasonably consistent maintenance, standard plaster has a life span of approximately 20 years. It is an inherently strong surface, and should be able to withstand real world chemistry and/or maintenance challenges.

Though pozzolans, blended cements and other materials are generating good results, there is still no substitute for solid workmanship. The above guidelines will benefit pool plasterers in the pursuit of a quality, long-lasting pool finish.


For how to personally supervise the plastering process, see this link: A Plastering 'Watch List' | Professional Watershaping | Watershapes

For further info on plaster discolorations and defects, see this post: Being Blamed for Plaster Discolorations? Don't Get Hoodwinked
 
Last edited:

Beez

LifeTime Supporter
May 19, 2009
785
Dallas, TX
That's fantastic information and I appreciate the time you put into your post. However, how is a consumer to use it? Seems like we are still at the mercy of the plastering outfit to do the job right. Kind of makes me nervous knowing how many ways they can screw it up...
 

onBalance

TFP Expert
LifeTime Supporter
In The Industry
Jul 25, 2011
974
Utah
I believe that pool owners can discuss these guidelines with their Builder or plastering sub-contractor and let them know that you understand some of these issues. When asking for bids, you can ask if they will follow the above guidelines. Some of them already do. The one that agrees should be the one you hire.

You can watch them, make notes, film them, and even pay a little extra for them to slow down by not adding a high content of calcium chloride and adding water while troweling. It would well be worth the price. And one important thing I forgot to include in the above post, is to suggest to the pool owner to take two paper cups and scoop in two different plaster samples of a recently mixed and fresh plaster material (before it is applied to the pool and hardens) and keep for future analysis if something goes wrong.
 
  • Like
Reactions: tessv

bg22

Well-known member
Aug 2, 2011
45
Texas
I wish I could have found your guidelines last year before our pool was built. I have a few spots in our pool/spa that are questionably over troweled with water and feel very porous, rough in a few spots. We had a reputable builder so it may not be much of a problem to get it corrected. Plaster is only 9 months old as well.
 

Beez

LifeTime Supporter
May 19, 2009
785
Dallas, TX
onBalance said:
I believe that pool owners can discuss these guidelines with their Builder or plastering sub-contractor and let them know that you understand some of these issues. When asking for bids, you can ask if they will follow the above guidelines. Some of them already do. The one that agrees will be the one you hire.

You can watch them, make notes, film them, and even pay a little extra for them to slow down by not adding a high content of calcium chloride and adding water while troweling. It would well be worth the price. And one important thing I forgot to include in the above post, is to suggest to the pool owner to take two paper cups and scoop in two different plaster samples of a recently mixed and fresh plaster material (before it is applied to the pool and hardens) and keep for future analysis if something goes wrong.
Once again, thanks so much for your time and expertise. I will be going through this process in the coming years(crossing fingers and toes).

I get discouraged sometimes when I read about a replaster job lasting only around 10 years. Whoever did the plaster job in my pool really knew what they were doing. The pool was built in the late 1970s and it still has the original plaster. Yes it is kind of rough, but no delamination or any areas of looseness. It's in great shape for being 30+ years old!!!

Hopefully when the time comes for reno I will be able to find similar craftsmen.
 

onBalance

TFP Expert
LifeTime Supporter
In The Industry
Jul 25, 2011
974
Utah
I really believe pool owners can influence pool plasterers by simply telling them to not add more than 1 lb. of calcium chloride to 100 lbs. of cement, and telling them to not use excessive amounts of water while troweling towards to end of finishing. (They could sign a letter of statement for you). If plasterers time the troweling correctly and have enough personnel, they only need to lubriate their trowel slightly with some water, and perform the final troweling.

On very hot and dry (non-humid) days, plasterers should place a tent or sun screen over the pool to slow down the hardening process, so that they don't need extra water to re-work the plaster.

Tell your plasterer to make the plaster mix thick like oatmeal, and not soupy. Then take some pictures during the plastering process, then the plasterer will hopefully be extra careful to do the job correctly.

I know of many pool owners that have had no problems when they communicated the above standards with their pool contractor. And now they have a good plaster job that is going to last more than 20 years with a good maintenance program. Far more than what is advertised by the NPC.

I worked for my father who owned a pool plastering company, and our plaster jobs were lasting twenty years. I have also been servicing pools for over 35 years, and I know that most plaster jobs do and will last 20 years. Performing good workmanship practices is the key. Just make sure your contractor is aware of and agrees with the above plastering standards.
 

vman1

Member
Oct 8, 2012
15
Orange, CA 92866
Wish I read this prior having our pool replastered. Its a colored plaster (light gray) with quartz.
The stains and discolored areas are probably results of techiques used by the plastering Co.
They did use calcium chloride (which I read shouldn't be used in colored plaster)
And they started filling the pool as soon as the last guy walked out of the pool.
I cannot tell if they used water when troweling because I wasnt home, but the marks on the surface described here looke dlike they did.
I have been trough **** last 5 plus months since they replastered the pool and spend close to $600 worth of chemicals that I probably
wouldn't if they did everything right. Just recently I had to drain about 1/4 of the pool because of high TA and high Ca which was direct result of
them trying to neutralize the pool with soda ash after in pool aggressive acid start up, they used 16Gal in 28K Gal pool (which only helped the stains partially).
I think they did what they thought were hired for. Plastered the pool. Do I like the result ? No.
6K for quartz I don't think was a bargain where I would settle for lower quality finish.
 

Lykly

Gold Supporter
Nov 6, 2015
912
Ok ok
This thread will prove to be very valuable to me, I intend on a plaster job in the next few weeks. I will discuss all of the recommendations with the individual doing the job. He's been doing it for over 20 years so hopefully he will understand. I want to confirm one thing, he said as long as the temperatures remain ~40° or above, I will be good. Is this accurate? Where I live when this job is done the temperatures will likely be highs of 50s and 60s lows around 40 possibly a few degrees cooler. He says that is good weather?


Sent from my iPhone using Tapatalk
 

-Matt-

Member
Jun 10, 2018
12
Huntington Beach
I think it is ok to necro this thread since is pretty much a stickie, is or is should be. Wouldn't hurt for it to have more traffic in any case. I have read many of OnBalance's texts across the web and as a non-experienced pool owner, but yet technically educated fellow, I tend to value their opinion.

Another important issue now, which I am currently facing is a industrious DIYer is, what pool trowels are right for the job? There are "no burn" plastic and even chrome ($$$) trowels on the market for pools and white portland cement. (Not to mention companies saying that their diamond polishing pads are the only non-corrosive ones on the market, pretty sure 90% are made with resin).

Is there, OnBalance, a problem with plasters using stainless (or carbon) steel trowels? Have you seen much or even any troweling issues due to corrosion? It is unclear to me what exactly these sellers and trowel companies mean by trowel burn as it seems stainless, chrome, or plastic I could push hard enough to compress white plaster so it is darker in areas. What trowels are acceptable for workers to use?

Thank you.
 

onBalance

TFP Expert
LifeTime Supporter
In The Industry
Jul 25, 2011
974
Utah
Stainless steel trowels are commonly used for pool plaster.
You are correct that any trowel can darken plaster due to late hard troweling. Timing is important.
 

x Wild Bill x

Well-known member
May 5, 2016
53
Rochester, MA
Anyway to make this thread a sticky? I just saw it for the first time and while we have a vinyl liner and will most likely never have a plaster pool the thread contains invaluable information for people having plaster pools built. I also think it would help out a lot of people that are trying to select a pool plasterer. IE, if they do not acknowledge or understand the advice here they may not be hired.

Great information, thank you for taking the time to write it up, onBalance!
 
  • Like
Reactions: tessv

onBalance

TFP Expert
LifeTime Supporter
In The Industry
Jul 25, 2011
974
Utah
The water/cement ratio is based on weight, and to the cement content only. The aggregate weight is not to be included.
Water weighs about 8.34 lbs. per gallon. Therefore, one would add about 5.5 gallons of water to a typical 94 lb. bag of cement.

Thank you for that question.
 
  • Like
Reactions: mikes112 and Oly

mikes112

Well-known member
May 28, 2019
47
New Jersey
I did exactly as you said in terms of proportions but used Sika Pro concrete bonder instead of water which is just about as thin as water, and used it in the same proportion as water and the plaster came out pretty good I think but there was a little cracking in a few small areas which ill just have to fill in. I did like 3 big patches about 3/4" thick. I reccomend dry mixing the white portland cement and marble dust first before adding in the water or liquid bonder. I did scrub with a steel wire brush and vacuumed and wet out the the areas with a spray bottle before I poured in the plaster. It was about the consistency of mustard. It was a little bit gritty when I poured it. I used three small containers to convert weight to volume. I admit my plaster work is not that smooth, but its a lot better and cheaper then calling some contractor idiots whos just going to mix what ever they want. I don't know if those cracks go all the way through. Those areas are thick. Just want to get the pool water tight. I guess I could smooth them over. The rest of my plaster is pretty good, but pretty well stained. Cider Crete sells a roll on pool plaster, wish I could thin this stuff out to get it so I could roll it on.
0930190737.jpg0930190735a.jpg0930190735.jpg0930190735_Burst02.jpg
 
Last edited: