How to Use Expanding Foam to Fill Household Cracks

Written by michael davidson
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How to Use Expanding Foam to Fill Household Cracks
Cracks can get worse over time if they are not filled. (John Foxx/Stockbyte/Getty Images)

Cracks can form around the home for a number of reasons. A water leak can result in wall or ceiling cracks. The building could be settling due to gravity, weight and age. Impact often results in cracks forming in drywall. Expanding foam is a home repair tool designed to make cracks less visible or noticeable while also providing a quick and cost-effective repair. It is important to use expanding foam correctly to fill cracks effectively.

Skill level:
Moderately Easy

Things you need

  • Soft cloth
  • Mild detergent
  • Spray bottle
  • Attachment nozzle

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  1. 1

    Clean the surface you are about to fill. Drywall can be dusted off with a soft cloth to remove dirt and dust prior to foam usage while other surfaces can be scrubbed with warm water and a mild detergent.

  2. 2

    Apply masking tape to any fixtures near the crack to ensure they are not exposed to the foam upon application.

  3. 3

    Spritz the surface with water from a spray bottle to moisten it if it has dried after cleaning. This helps the foam bond with the material in the wall crack.

  4. 4

    Shake the foam can thoroughly to ensure the foam contents are properly mixed prior to application.

  5. 5

    Place an application nozzle on the can of foam. The size of the nozzle is dependent on the size of the crack you are filling. Follow instructions on the package when choosing which nozzle to use.

  6. 6

    Position the can upside down so the foam is flowing down into the nozzle. Always aim the can away from your face.

  7. 7

    Test the can by lightly pressing the button to ensure the nozzle is appropriately tightened and that the foam appears to flow properly.

  8. 8

    Aim the nozzle at the lowest point on the crack and slowly fill the crack from the lowest point up to the top. Add another layer if needed but add more water to it first. The foam will often expand to about two and a half times the size of the initial application so allow it to dry before deciding if a second layer is needed.

Tips and warnings

  • Once the foam has completely dried after about 12 hours, sand or paint over the foam as needed to blend it more into the wall.
  • Wear gloves when using the foam to prevent contact with the skin.

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