10 Smart Uses For Expanding Foam

Expanding Foam

gwmullis / Getty Images

Like duct tape, expanding foam is one of those household products that can be used for far more than its intended use. Hacked in innumerable ways, expanding foam finds its way into bathrooms, kitchens, and ceilings, and it even works outdoors under concrete walkways and rocks.

Expanding foam is meant to fill small wall cavities that are difficult to reach. It also seals gaps to resist weather intrusion. Normally, you'll find expanding foam in basements and crawl spaces, filling gaps along the seal plate. It's also used around doors and windows to fill gaps and prevent air intrusion.

Expanding foam—expansion foam or spray foam—is can-based polyurethane or isocyanate thermal insulation. When first sprayed, it is a thin liquid foam but expands to 30 to 60 times its original size after hardening.

  • 01 of 10

    Stop Pipes From Rattling

    Water pipes that rattle when the water is turned on or off eventually become part of the soundtrack of our daily lives. But why should they, when you can fix the problem with a little expanding foam?

    Spray low-expansion foam between the pipe and the structural element it rattles against. Usually, this is a penetration through a joist or stud.

  • 02 of 10

    Protect Your Fragile Items

    For a delicate electronic device or any valuable item that you need to ship or store, you might need something more than wadded paper or bubble wrap to prevent the item from moving around and possibly getting damaged.

    You can create form-fitting, clamshell-style padding with expansion foam. You'll need thin plastic (like food wrap), the item that you want to protect, a cardboard paper towel roll, and a box that's about three times as large as the item.

    1. Wrap the item tightly in plastic. Make sure that all areas are covered, to prevent the foam from touching the item.
    2. Line the inside of the box with plastic.
    3. Cut off a section of the paper towel roll to create a stand for the item. The stand should be high enough to elevate the item in the center of the box.
    4. Use expanding foam to fill the box below, around, and above the item. Work slowly and keep in mind that expanding foam does expand.
    5. Let the foam fully harden. This can take as long as 24 hours.
    6. Slide the hardened foam block from the box. Peel off the plastic.
    7. Use a dull knife to cut the hardened foam block in half, like cutting into a loaf of bread. Cut perpendicular to the cardboard roll holder. Cut slower and more carefully when the blade reaches your item.
    8. Remove your item from the block. Remove the plastic from the item. When you replace the item, it will have custom-made padding around it.
    9. The paper towel roll holder cannot be removed from the foam, but you can fill in the hole with more foam.
  • 03 of 10

    Make a Multitude of Crafts

    Anything crafty and three-dimensional that you can imagine can be formed or carved out of expanding foam. Build mountains, volcanoes, and landscapes with high-expansion foam. Large, formless blobs of hardened expanding foam can be sculpted with a serrated knife.

  • 04 of 10

    Fill Voids Below Concrete

    The space below exterior concrete walkways or patios can eventually crack, so they need to be filled in. If you have access to the void from the side, forcing in soil or sand won't be enough. Instead, inject high-expansion foam into the area until it oozes out.

    Continue to 5 of 10 below.
  • 05 of 10

    Silence a Noisy Metal Sink

    Metal kitchen or bathroom sinks can be loud when they are used. One way to dampen the sound is to apply low-expansion foam to the bottom of the sink.

    It's a delicate process since you need to work upside down. Work slowly and apply only small amounts at a time, letting each layer section harden before moving on.

  • 06 of 10

    Stabilize Shaky Showerheads and Faucets

    Showerheads that move and rattle are more than just annoying—if they rattle long enough, they may begin to leak.

    Since it's not usually possible to get behind the shower wall to secure a loose showerhead with a strap, the next best solution is to inject expanding foam behind the wall where the shower head emerges. Protect your shower surface as you do this, use low-expansion foam, and go slowly.

  • 07 of 10

    Hold Rigid Foam in Place

    Sheets of rigid foam do a great job at insulating high moisture areas, such as basements, but they do not fit wall cavities very well.

    While the best solution is to install rigid foam behind the wall studs, this isn't always possible or easy. Low-expansion foam can help fill in the inevitable gaps between the edges of rigid foam and wall studs.

  • 08 of 10

    Build Waterfalls and Streams

    Exterior garden ponds, waterfalls, and streams often use natural rocks as decorative elements, but it can be tough to get them to stay in place, especially with water running over them.

    Use black-colored expanding foam in minimal amounts under or around the stones to secure them to the lower surface and on their sides to attach them to each other. Expanding foam is waterproof, so it will not be affected by splashes from the water feature.

    Continue to 9 of 10 below.
  • 09 of 10

    Soften Thumps From HVAC Vents

    HVAC cooling or heating vents that thump when they warm up or cool down can be softened by injecting expanding foam at key locations, as long as you have access to the area. 

    First, identify the section of the vent that thumps. Next, spray expanding foam to bridge the gap between that area and the closest structural element, such as a joist or wall stud.

  • 10 of 10

    Help Your Cooler Stay Even Cooler

    Plastic coolers for beverages and food typically have hollow lids. While hollow spaces can provide some thermal insulation, filling that space with expanding foam does a better job.

    With a drill, make at least two holes on the inside of the cooler's lid. Fill one hole with expanding foam. Foam will ooze out of the second hole. After the foam has hardened, slice off the excess.