Pool Info: Pool Expansion Joint Caulking
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 rather stopped mentioning it, or switched the responsibility to the pool owner. It is well worth mentioning.
Why is Pool Caulking Needed?
Caulking the expansion joint around the pool (between the pool coping and pool deck) is important for two reasons. First, caulking keeps out water, which can freeze and expand in the joint during winter. The 10% expansion is enough to damage the coping, beam and eventually the tile. Ice in the expansion joint can be very destructive over time. The second reason is to prevent the expansion joint from filling up with sand and dirt. Over many years, material building up in the expansion joint will absorb the movement of the pool and transfer it to the pool deck, or vice versa. When the joint is full of debris, there is no air space left for expansion of the pool or pool deck, and when they expand, they bump into each other, with the horizontal pool deck usually winning out over the weaker, vertical pool wall.
What is a Pool Expansion Joint?
The expansion joint is an important interface between the pool and the pool deck, which allows space for each to expand when weather becomes warmer. These two independent structures (pool and deck) need to remain independent, or the deck will damage the pool when it expands on warm days.
Keeping debris out of the joint ensures that the joint is "true", all the way to earth, and the two structures are not in contact with each other. When they do come in contact, or move as one, the pool will lose the fight, and may develop a crack in the tile, which is usually an indication that the "beam" has cracked all the way through.
How do I Caulk my Pool?
A good caulk job starts with good surface prep. The sides of the joint must be clean, dry, rough and solid. Use a razor knife to remove bits of old caulking, and a wire brush to remove dirt. Use a pressure washer if possible, to remove grime and gunk, and blast out the debris in the joint. Allow the joint to dry fully for several days before caulking, use a leaf blower if you want to accelerate drying.
Backer rod foam should be placed in the joint (don't use sand!) to give the caulk some support, so that you don’t have to use too much caulk, and so that the caulking won’t sag or run down into the joint. Use a foam backer rod of sufficient width, so that the foam fits tightly in the joint, and push it down to a consistent depth all the way around, about 3/8” from the top of the coping / pool deck.
The joint is taped off with wide masking tape to keep things neat, (deck must be dry for tape to stick) and caulk is squeezed in or troweled into the joint to a depth of 1/4 - 3/8" (self-leveling caulk requires no troweling). Move around the pool with a large piece of cardboard and keep a rag handy for spills or drips. Tie up the dogs and kids for 24 hrs. Remove the tape before caulk sets.
How often is Pool Caulking Needed?
Replace or repair caulking when it cracks or pulls away from either side, or has become deteriorated. Most good caulking jobs can last 5 years, more or less. It can be one of the more frequent repair jobs done around a pool, and also one of the most important. Pool caulk can be patched or repaired in small areas that pull away from the coping or deck, or if holes open up in certain areas, but eventually, it will need to be cut out and replaced, every 5-10 years.
What type of Caulk is used for Pools?
The caulk used for pools should be an elastomeric sealant, suitable for outdoor use. EZ Patch 23 and Vulkem SSL are popular sealants suitable for caulking pool expansion joints. The large quart size (32 oz) tubes are much more convenient than using dozens of small 10 oz. tubes. You can find the larger quart size caulking gun at any home or hardware store.
Cost to Caulk a Pool?
Prices for professional pool expansion joint caulking runs $5.00 - $8.00 per linear foot. Measure or add up the perimeter of the pool to figure your price. The range in price depends on the width of the joint, which is usually 1/2" - 1", or regional differences in pricing. Price includes full prep, backer rod, caulking and finishing.