Caulking vs Sealants: What South Florida Property Managers Should Know

The Short Answer

Caulk is for joints that barely move. Sealant is for joints that move a lot. On a South Florida commercial building, putting the wrong one in the wrong joint is a common reason joints fail early. The right choice depends on how much the joint moves, whether it will be painted and where it sits on the building.

The Difference Between Caulk and Sealant

Caulk is usually an acrylic latex product. It sticks to most surfaces, takes paint well and works on joints that do not move much, mostly indoors and on low-movement outside joints. It is not made to stretch over and over.

Sealants are made from polyurethane or silicone. They stretch and squeeze with a moving joint without cracking and keep their grip through years of heating and cooling. Silicone usually cannot be painted. Polyurethane can, which is why it is a common choice for outside joints on commercial buildings here.

Where Each One Belongs

Use caulk for:

• Painted indoor joints such as baseboards, trim and inside window edges
• Outside joints that barely move and will be painted
• Filling small gaps on sound surfaces before coating

Use sealant for:

• Every expansion joint on the outside of the building
• The edges of window and door frames on outside walls
• Pipes, conduit and equipment lines that pass through the wall
• Joints in the caps on top of parapet walls
• Joints where two different materials meet, such as a metal frame against concrete

A common mistake on commercial buildings here is paintable acrylic caulk in an expansion joint. Expansion joints move a lot as the building heats and cools. Acrylic caulk is stiff once it cures, so it cracks when the joint moves. Our commercial caulking services cover matching the right product to each joint. Joints that have already failed are expansion joint repair work.

How South Florida Weather Wears Out Joints

Heating and cooling come first. Commercial walls warm up in the afternoon and cool at night, and every cycle squeezes and stretches every joint. Products that cannot handle that movement crack and let water in.

Sun is next. Strong sun breaks down sealants. Silicone handles it well. Polyurethane needs a sun-resistant version. Acrylic caulk on sunny south and east walls wears out well before its label suggests.

Salt air is last. Buildings near the ocean, including those in Palm Beach, Boca Raton, Delray Beach and along the Fort Lauderdale beachfront, should expect joints to wear out at the short end of any product's range.

Three Mistakes That Make Joints Fail Early

The wrong product for the joint: acrylic caulk in an expansion joint will fail no matter how carefully it goes in, because the joint moves more than the product can handle.

New over old: fresh caulk over old caulk sticks to the old layer, not the wall. When the old layer lets go, the new one goes with it. Old material should come out first.

Skipping primer: polyurethane sealant on bare concrete or masonry without the right primer loses its grip sooner. The primer should suit both the surface and the sealant.

If the building is due for a new finish too, reseal the joints first, then move on to commercial painting. On cracked walls, commercial elastomeric coating is often the better finish. Our commercial waterproofing checklist covers the rest of the building.

Ready to Have Your Building's Joints Checked?

Anthony Pennacchi & Sons checks and replaces joint sealants on commercial buildings across Palm Beach County and Broward County. We work throughout South Florida. Call (561) 475-0775 to set up an assessment. FL License CGC1538576.

Where failed joints have already let water into the walls, our commercial waterproofing services look at the whole outside of the building alongside the caulking.

Frequently Asked Questions