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How to use Expanding Foam

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Expanding foam is a can of liquid that quickly expands and hardens once sprayed. Once dried, it can be trimmed, sanded and painted. It is ideal for sealing gaps around pipes and wires; essential for energy efficiency, to keep your home warm.

Step 1

Clean Area

Clean Area

Using a large, dry paint brush, sweep away any dust or loose particles in and around the area. When the area is clean, spray it lightly with water. Expanding foam needs moisture to cure, so this will help the foam cure evenly.

Step 2

Spray Expanding Foam

Spray Expanding Foam

Before applying the expanding foam, read the manufacturer’s instructions. Expanding foam is a skin irritant so it is essential to wear protective gloves during its use. The expanding foam is applied using a gun or nozzle that comes with the product. Attach the nozzle and shake the can thoroughly. Hold the can upside down, insert the nozzle into the area to be filled, and apply the foam carefully bearing in mind it will more than double in size once applied.

Step 3

Moisten Foam

Moisten Foam

Immediately after applying the foam, mist it with water. If you apply more than one layer of foam, spray water between each layer to help the foam adhere. Leave the foam to cure fully, which usually takes one hour depending on the manufacturer’s instructions.

Step 4

Trim Off Excess Foam

Trim Off Excess Foam

When the foam is fully cured, carefully use a hacksaw to cut off any excess.

Step 5

Sand Area

Sand Area

Use sandpaper to sand the foam and give a smooth finish. The expanding foam can now be plastered or painted over.