In this article I would like to help you make an informed decision on the bottom finish of your new or remodeled pool.
The “bottom finish” is considered the finish on the bottom of the pool, and for in-ground gunite swimming pools and spas this may be a plaster or tile finish. Mosaic glass tile has become very popular for swimming pool bottom finishes but is usually reserved for the rich and famous! Being that this is DIY Pool Plans and you are looking to save some green, we will concentrate on the plaster finishes.
In the industry; the term “plaster” may be used for standard plaster, quartz plaster, pebble plaster or a variation that may include glass beads or some kind of hybrid plaster that has a combination of plasters and finishing technique. The most commonly used finish is still standard white plaster; this is probably due to price. There are a few more things to consider, other than price, when making the decision about how the bottom of your pool will look and function. Let’s take a look at each of our options for bottom finish to help make our decision. We will try to keep this informative and not to clinical…
Standard White or Colored Plaster Finish:
Standard white plaster is basically made of white cement and crushed marble. Standard white plaster is the original plaster which was used on your grandparent’s pool. It is funny because we get requests quite often to design a pool with the same light blue color of plaster that the client had when they grew-up. Believe it or not, those pools built mostly before the 80’s were finished with snow white plaster. They were, however, plumbed with some or all copper plumbing and over the years copper was stripped from the pipes and attached itself to the plaster. The patina copper appears blue or sometimes green on the walls and floor of the pool.
Today’s swimming pools and spas are designed and built with PVC pipes and copper is no longer part of the plumbing. White plaster gives the pool an inviting light blue hue and a classic look and will stay white with proper maintenance. Standard plaster is the smoothest finish of all the plasters.
White plaster is considered by the National Plasterers Council as a “soft” product when compared to other finishes. Standard plaster is hand troweled like the other finishes, but will tend to show trowel marks more easily. Standard plaster is more susceptible to damage from imbalanced pool chemistry which can result in slight shading, scaling, staining, etching, cracking or delaminating in extreme cases. Standard plaster will have the greatest chance to change appearance over time.
There are hardeners called “pozzolans” which can be added to the plaster mix. Pozzolans change the chemistry of the cement and make the plaster more impervious to the effects of poor chemistry. There are also silicon additives which can be added to help maintain the plaster finish. There is an additional expense to additives and it is not a complete solution to countering the effects of pool chemicals and environmental effects on your plaster.
Standard plaster can also be colored and it commonly referred to as just “colored plaster”. Simple huh? Colored plaster is white plaster with colored pigments added in the mixer before application. Colored plaster can be any color but don’t expect an exact match from a color sample. Colored plaster will usually change color and fade over time. The most popular color is varying shades of grey.
There are soooo many complaints about colored plaster that many plasterers have stopped offering it as a bottom finish. Those that do offer it will have you sign a long disclaimer about all of the inconsistencies with colored plaster. Here is a list of common complaints about colored plaster which are considered acceptable by plastering standards: Mottling, pigment stains, streaks, unevenness of color, variation between color and sample, checking and crazing.
Checking and crazing refer to a type of superficial cracking that looks like the spider cracks on aged china dishes. In fairness all plaster has some degree or checking and crazing but it is more easily seen in colored plaster.
If you are still interested in colored plaster then you will enjoy the mottled look with a beautiful colored pool, and save some money over the other finishes. It also offers the same smooth finish as white plaster.
Quartz finish has gained popularity because it is a very durable finish but costs less than pebble finishes. Quartz plasters are made by several manufacturers and each has a different claim about how their plaster is better than the rest. Any plaster is only as good as the plasterer installing it and a reputable company will probably use a product they can stand behind.
Quartz plaster is made the same as standard plaster but the sand is replaced with crushed quartz stone. There are polymers offered to strengthen the mix; in place of the pozzolans used in standard plaster. Quartz stone is a very hard and dense stone but a big difference is in the application.
After the plaster is troweled and the curing process begins, special water nozzles are used to strip the plaster surface away and expose the quartz. This gives the surface a more durable finish which also has a sheen. Colored quartz stone can be added to the mix for a different look and the base plaster can be colored to give the pool a beautiful look.
Many of the concerns with standard colored plaster are not a problem with a quartz finish because the top layer of plaster has been stripped away. This gives the plaster a greater color consistency and less issues with the appearance of crazing. Quartz finishes are very smooth and have a similar look to standard plaster.
A pebble finish is known in the industry as an aggregate finish. A common misnomer in the pool industry is to call a pebble pool finish “Pebble-Tec” but that would be like calling every pair of jeans “Levi’s”. Pebble-Tec was the original company to patent the process and has the greatest recognition, but just like the quartz finishes there are many manufacturers who make pebble or aggregate finishes.
A pebble finish is obtained much like a quartz finish. Small polished stone is added to the plaster mix (usually a standard plaster) and hand troweled onto the gunite surface. As the plaster starts to cure, special water nozzles are used to strip the top layer of plaster which exposes the pebble. A big difference here is that the majority of the surface is all stone as opposed to a quartz finish where it is a mix of plaster and quartz.
The pebble finish when complete is a solid layer of polished stone with the colored plaster mix peeking through the space between the stones. Each manufacturer offers different sized stone to give each pool a different look. Some stone is colored and some have more consistent shades.
I have always described a pebble finish as “inconsistently consistent”. I never said it fast five times… If that does not make sense, it means that there is so much inconsistency in the surface that it makes it a consistent color. Pebble finishes are rich in color and have subtle color changes with the depth of the pool. A tan color shows the most dramatic change in color. The shallow steps will show the true golden tan color but as the pool gets deeper the water takes on a beautiful emerald color.
Pebble finishes are superior in durability. The exposed surface is made-up of solid tumbled stone. They are impervious to fading and chemical reactions. Aggregate finishes also have a long track record, so don’t feel like you would be testing out new technology.
As with the other finishes there are additives to strengthen the plaster behind the pebble. Similar aggregate finishes are now available which contain glass beads or other materials like abalone shell.
You have probably already guessed that this option is the most expensive. The cost will be over double the cost of standard plaster, but this where you need to consider the longevity and look of pebble over price.
Ultimately you will have to make a tough (and fun) choice about the finish of your pool. Get a bid for each type of plaster so you can make an informed decision. Ask your sub-contractor to look at other swimming pools to see the finish you like. Remember, building a swimming pool is about a creating a lifestyle to surround family and friends with the beautiful outdoors. You will make that dream a reality with any plaster you choose. PLAN, BUILD, ENJOY!