It used to be that all pools built had the expansion joint between the perimeter coping and the pool deck caulked or filled with elastomeric sealant 30 days after the concrete was poured. This was holding up the checks to the builders, I was told, so they sort of stopped mentioning it.
It is well worth mentioning. The expansion joint is an important interface between the pool and the deck. These two independent structures need to remain independent. Keeping debris out of the joint ensures that the joint is “true” and the two structures are not in contact with each other. When they do come in contact, the pool may develop a crack in the tile, which is usually an indication that the “beam” has cracked all the way through. The beam is defined as the top 6 or 8 inches of the pool wall which holds the tile & coping. Beam damage gets worse with time, eventually crumbling, requiring beam reconstruction. To avoid this costly expense, caulk those joints! Caulking also keeps out water which can freeze and expand. This can damage the coping, beam and eventually, the tile.
A good caulk job starts with good surface prep. The sides of the joint must be clean, dry, rough and solid. Backer rod foam should be placed in the joint (don’t use sand) to give the caulk something to sit on top of. The joint is taped off to keep things neat, and caulk is shot or troweled into the joint to a depth of 3/8 – 1/2″. The caulk should be an elastomeric sealant, suitable for outdoor use. Deck-o-Seal and Vulkem are two popular brand names. Tape is removed before caulk sets. Replace or repair caulking annually if it cracks or pulls away from either side.
Prices for professional expansion joint caulking run $5.00 – $8.00 per linear foot. Add up the perimeter of the pool to figure your price. The variance depends on the width of the joint, which is usually 1/2″ – 1″ or regional differences. Price includes full prep, backer rod, caulking and finishing.