How to Use Polyurethane Foam

Polyurethane foam is an extremely useful material for many types of construction. It is important to keep in mind that this product is expansive. Expansive means that when you apply a small quantity, it expands to a larger quantity. The key to getting the desired results from using polyurethane foam is to find out before you apply it the amount of expansion you will get for the amount of foam you apply. Practice applying different amounts of polyurethane foam to a scrap piece of material until you are comfortable with gauging the expansion.

  1. Read all instructions prior to use. This will help you determine exactly how to protect your skin and eyes. You should always wear safety goggles, but specific products may recommend additional precautions. Use a dust mask or respirator as directed.

  2. Make sure that you are working in a safe environment. If you are using polyurethane foam inside, provide adequate ventilation as directed.

  3. Clean all surfaces that polyurethane foam will be applied to. You can wipe the area down with a dry rag, or if you are using a spray cleaner, be sure to wipe off the area with a dry rag after you have cleansed it with a wet one.

  4. Shake can as directed. These instructions are for premixed polyurethane foam sold in a can.

  5. Assemble the application apparatus. Remove package containing straw applicator from outside of can. Open the package and remove the thin straw. Attach straw to nozzle on can. You will hold can away from you when you apply foam.

  6. Practice on a piece of scrap material to gauge amount of expansion of foam. You should apply the test polyurethane in the same conditons as you will be applying the polyurethane in your real construction project.

  7. Squeeze trigger and apply small amounts of foam. If you are using polyurethane foam to seal around a window or door, wipe off any excess foam after applying. Allow expansion to occur before you apply more foam.

  8. Spray additional foam if needed. Once polyurethane foam is applied, it will expand. After full expansion occurs, foam will dry and harden.

  9. Cut or scrap off any hardened foam that is not desired from adjacent surfaces. You can use a pocket knife for this part of the process.


  • Follow all safety precautions to the letter. Wear safety goggles and work in a well ventilated area. You may also want to wear gloves.
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