How to Stop Condensation on a Suspended Slab

Put on the safety goggles and respirator to protect your eyes and lungs from falling foam particles. Put on a pair of work gloves as well to avoid contact with the foam as it leaves the sprayer.

Attach the sprayer hoses to the two component tanks of the sprayer, matching the color of the hose with the color of the tank connector. Both hoses lead into a single dispensing unit. Spread a thin layer of petroleum jelly onto the head of the dispensing unit to prevent curing foam from sticking to the unit’s face. Push a fan nozzle onto the front of the unit until you hear a clicking sound, indicating that the nozzle is in place and ready for use. The fan nozzle will allow for a wide dispersal of the foam from the sprayer onto the concrete slab.

Turn the valves of the tanks open fully to begin the flow of the foam through the system. The foam is pressurized, so all that’s needed to dispense the material is that you press the trigger of the dispensing unit.

Position yourself beneath the suspended slab with the nozzle of the sprayer held about 8 inches from the slab’s surface. Aim the nozzle directly towards the slab and begin covering the surface with a 6-inch layer of polyurethane foam, built-up using 1-inch layers.

Spread the foam over the slab in rows, moving beneath the slab as you spray along the slab surface. Keep the spray constant when applying it to the slab, taking care not to stop spraying for longer than 30 seconds, as you’d need to change the nozzle before you can begin again.

Change nozzles often, as the material cures within the nozzle at the same rate as it does on the slab.

Twist the valves on the component tanks closed when you finish covering the slab, and then clean out the nozzle by flushing it with a solvent to dissolve any cured foam.

Allow the foam under the slab for 1 hour for quick cure foams, otherwise, wait the manufacturer recommended period of time.