Also Known As: Perimeter caulk, Expansion Caulk, Building Border, Caulking

A waterproof filler and sealant, caulk has a variety of uses in and around the pool or spa. When properly applied and maintained, caulk can prevent erosion and damage, as well as maintain safety.

Expansion joints around the pool should be sealed using a polyurethane sealant. This caulk may be paintable and is also suitable for underwater treatments. The sealant may be layered, troweled, injected or brushed into the joints. However, using a caulk gun is the most common application process. A polyurethane sealant is moisture resistant and blocks corrosion and chemicals. It is also very flexible, which is important when applying around curved and angled areas.

Self-leveling caulk is runny, but it requires no taping on either side of the joint. There is also no need for a finishing bead. Because it is so viscous, it can run downhill and may pool in low-lying areas, so it is typically used on perfectly flat joints. To prevent pooling, one open-ended joint should be taped or puttied before application. Semi, self-leveling caulk is less runny, while traditional leveling caulk is even more solid. Mask or putty each end of the joint before sealing with traditional caulk, then trowel it smooth.

Existing caulk that is split, cracked or pulling away, should be replaced. All of the caulk should be removed and the joint cleaned well before reapplying. In addition to expansion joints, caulk can be applied to deck cracks, building borders, deck expansion joints and walkways.