Why do I need to replaster my pool?

This is a great article that my new friend Rob Cox wrote on replastering pools! He has many more great articles on pool care here: Rob Cox Pool Blog

by Rob Cox, 

When is it time to Replaster the Pool?

I've just returned from a board meeting for one of the local swimming pools I help with. A budget line item for "Pool Whitecoat", (which is what the commercial pool guys call pool plaster in this area), caught my attention. Enough money was being set aside to replaster the pool every ten years. In a commercial environment, with picky health inspectors and kids complaining of "pool toe" - this may be a good time interval for replastering.

But how about residential pools? How often should they be re-plastered? And what factors should a pool owner consider when looking at replastering or resurfacing their swimming pool? Surely, Time cannot be the only factor to consider. When and Why should a pool owner replaster their pool?

There are really only two reasons for replastering your swimming pool

Aesthetic Reasons to Replaster the pool: The look and feel of your pool plaster. Acid washing can remove stains, but this can only be done so much. Pool plaster is a natural product, and preventing stains can almost be impossible. I have often been one to suggest a dose of tolerance with regard to pool stains, but some pool owners are very particular about the look of the pool - "...especially at night, with the lights on", they say.

If your pool plaster stains are mineral in nature, from copper or iron for example - be mindful about the source of these stains. Pity to replaster the pool, only to have stains return, because a mineral problem in the water, or from a copper heat exchanger or piping has not been addressed.

Some stains on plaster are not actually stains at all, but arise from the mix and application of the whitecoat. Pool plaster is a mixture of white portland cement and marble dust - and variations in mix, temperature and speed and methods of appliation can affect the final appearance. "White Lightning" or "Ghosting" marks - which are slight variations in hue or shading, can result from a slightly different mix or troweling procedures.

The "feel" of the plaster is also an important consideration. Plaster is meant to be smooth and soft. Agressive water chemistry or frequent or overly strong acid washing can create pits and pocks in the plaster surface. Commonly called "etching", plaster with pitting feels a bit rough to the skin, can snag swimsuits, and gives dirt a place to hide, and algae a nice surface to attach their roots. Etching can also be caused by poor plastering procedures, especially using too "hot" of a mix, or too much calcium used during cold weather. Rough Plaster can be sanded with rotary sanders to smooth etching, if localized, however if widespread etching occurs, replastering the pool is indicated.

Structural Reasons to Replaster the pool: Trick Title, because plaster is not "structural" - but it is the waterproof layer between the pool water and the shell of the pool. Most plastered pools are made of Gunite, or Shotcrete. Some older pools were made with poured concrete walls or even cinder blocks. All of these materials are porous and will "weep" water through them. Applying the plaster coating on top keeps the cement beneath, and any reinforcement steel (rebar) protected from the effects of water. Plaster is the waterproofing layer that is important to the integrity of an inground pool structure.

If you have bare spots where the gunite beneath is showing through, this is of concern. You can patch small areas with EZ Patch pool plaster repair, even underwater. Spots at the tile line or inside the skimmer can also be patched easily - to protect the concrete beneath the plaster. Plaster is fairly translucent in thin layers, so if you see dark areas in your plaster, this could be the gunite showing through, giving an indication that this area may need patching.

If you have many thin or bare spots in your plaster, replastering the entire pool is sure to produce a more uniform result. Plaster patching always looks like patched plaster - you will never match the original color. And, similar to filter grids, or car tires, if one is going bad, the rest are sure to follow.

How to Replaster the pool: Call three plastering companies in your area to give competing quotes. Be sure to ask about the start-up procedures. Don't try this at home, kids - there really is an art and a science to plastering pools properly. Done improperly, and you risk bond failure, crazing, shading, etching - all sorts of things can go wrong with trying to plaster your own pool. A small fountain can be done, if you are an experienced concrete person, maybe even a small pool, but medium to large pools have to be plastered quickly. I have watched many plaster crews in action, and they always amaze me. Four hours, start to finish, on a 40,000 gallon pool (just the plastering part, not including the prep work). They run a full plastering rig (truck), and five experienced crew members.

The best time to replaster is when weather is somewhat cool and humid. If done during high temperature times of the year, this can causing premature drying - before the pool has a chance to fill fully.