Expansion Joint Caulk on a Swimming Pool – Why?

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Many people wonder what the purpose of the expansion joint is on a swimming pool. The expansion joint is between the pool coping and the patio, and it’s job is just that, to allow for expansion and shifting of the patio so it does not press against the top beam of the swimming pool. In this photo you can see a gap and some shifted coping. This was the result of water building up under the patio when the prior patio trapped water in this area. The ground froze/expanded and pushed against the pool causing tile to pop, coping to unseat, and a horizontal crack in the pool.

Remedies: Homeowner replaced the patio, is in the process of a tile redo of the entire pool, and the team will reset the coping stones in this location.

Next we will remove some of the foam to make room for a new expansion joint with SilkaFlex caulk to seal the area from water penetration and ensure a flexible joint for future movement.