Question

What caulking or other material can I use to seal an aluminum Florida room to a concrete slab to water-seal the room?

Asked by JACK SHONTS
Clermont, FL

Room has an aluminum frame that is bolted to concrete slab with caulking along inner and outer wall to seal out rainwater, but it manages to leak a small amount into room during a heavy rain. Floor of room is the slab with indoor-outdoor carpet on it.

Answer

Jack,

Caulking is a maintainable joint and consistently requires inspection and repairs. 

In your situation there are two items working against you in keeping the water out.

  1. Expansion and contraction in the aluminum frame of the Florida room. Aluminum is susceptible to extreme amounts of expansion and contraction due to solar heat gain. It is this expansion and contraction which will continuously pull the caulk away from the concrete slab, creating gaps and allowing the water to infiltrate the interior of the room.
  2. Certain caulks do not adhere to concrete. This lack of adhesion aids the ability for gaps to become present during the movement in the aluminum frame brought on by the solar heat gain.

Preventing water infiltration

The best way to stop future infiltration is to properly install flashing, if possible, along the exterior parameter of the room.

If this is not feasible, I would recommend that you:

  • remove all of the caulk, installing backer rod (neoprene foam cord) between the aluminum frame and concrete creating a compression seal.
  • After the backer rod has been installed apply a premium polyurethane adhesive sealant to both the interior and exterior joint between the frame and concrete slab following the manufacturer specification for sizes of bead and tooling.

Finally, keep in mind that an applied sealant will require yearly inspections and repairs as needed.

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