The most durable of in-ground swimming pools are the various concrete versions. If you want a well-built swimming pool that won't need renovation for 15 to 20 years, a concrete pool is for you. Concrete in-ground pools can be made in any size or shape desired as well. Concrete swimming pools hold water in their basins through use of pool plaster topcoats. The layer of pool plaster applied to a concrete swimming pool's surfaces is also relatively thin but effective nonetheless.
Building a swimming pool from concrete and some form of water-resistant or waterproof plaster is the oldest form of pool construction. Basically, pool plaster is nothing more than a type of mortar that contains various other ingredients to give it colour and water resistance. Swimming pool plaster topcoats should be of no less than 3/8-inch thickness. An online look at several pool builders shows they apply plaster to in-ground concrete pool at thicknesses from 3/8 inch up to 5/8 inch.
The pool plaster topcoat for an in-ground swimming pool is applied over the top of a very thick (8 inches or more) layer of concrete. Like all other forms of plaster, pool plaster is mixed and then trowelled on by plasterers using traditional plaster application techniques. Typically, a concrete swimming pool's plaster topcoat is applied by 4 to 6 plasterers who work quickly to apply it before it sets and cracks. A pool plaster's specific ingredients determine how quickly it will set.
The main ingredients in pool plaster in the 21st century are Portland cement, water and some type of aggregate mixture. Portland cement in pool plaster is what gives it its nonporous, waterproof character. Water in pool plaster makes it malleable enough to apply, and aggregates in pool plaster help give it colour, texture and uniqueness in its finish. The most common aggregates added to pool plaster are white marble dust or white silica sand. Other pool plaster aggregates include quartz and smooth pebbles.
Several reasons exist for why a concrete swimming pool will need to be replastered at some point in its life. Eventually, any concrete swimming pool's plaster topcoat will become too abraded or rough for swimmer comfort. Also, plaster topcoats in concrete pools are made to gradually wear away over time. As of July 2011, replastering a concrete swimming pool costs from £1,625 to £2,600. Pool plaster pricing is based on surface square footage of the pool to be plastered.