Using Expanding Foam: What You Need To Know

Expanding foam is extremely useful around the home for many reasons. It is a can of liquid which, when sprayed, expands and then hardens quickly. When it is completely dry (which does not take long) the foam can be shaped, sanded, or even painted. It’s particularly useful for sealing holes and gaps, and it is great for keeping your home more energy-efficient. So just how should you use it? Here are some tips to get it right.

Clean The Area

Look at the area you want to use the expanding foam in and work out exactly where it is going to go. This is a great start, but it’s not enough to ensure that the foam will do its job and look great afterward; you also need to prepare the area by cleaning it.

It’s easy for small dust particles and other loose particles to land on a normal day, let alone a day when you happen to be carrying out DIY projects in your home. So it’s best to wipe around the area even if it looks clean. You can use a large (clean) paintbrush for the job, and simply sweep up any dust or other particles that shouldn’t be there.

When you are done, use a spray to moisten the area a little — expanding foam works best when it has a moist surface to cling to.

Spray The Foam

Unlike other DIY projects and tools, expanding foam needs little preparation to be used effectively, and cleaning and moistening the area should be enough. So once that is done, the next step is to apply the foam. Read the canister carefully and ensure you understand the instructions as each manufacturer will have their own.

One important point to be aware of is that expanding foam needs room to expand and therefore a little is going to go much farther than you might expect. In fact, once applied the foam will usually more than double in size. When using expanding foam, you must wear gloves as it is a skin irritant.

Moisten The Foam

Although you should ideally have already made the area the foam is to be applied to slightly wet, it is also good practice to moisten the foam once it has been sprayed in place. A light mist is all that is needed. If you do find that you need to add more foam, wait for an hour to ensure the first application has fully cured and spray again with water before adding any more – this will help the two applications adhere to one another better.

Trim The Foam

By its very nature, any expanding foam that you apply will grow larger, and it is not going to be possible to make it fit what you want it to cover or fill in the first instance. This is why you will need to trim the foam once it is fully cured.

Start with a hacksaw to trim off the excess – there may be a lot of it, especially if you haven’t used expanding foam before and have used a little (or a lot) too much.

Once you have removed the bulk of the excess foam, you can switch to a smaller saw or a knife to remove more.

Finally, when you have trimmed as much as you can, you should sand the area down so that it is flush with the wall. If you have used the expanding foam to insulate a pipe, this step is not necessary, but it will depend if the pipe is on view; you might want to trim and sand the foam to make it look better aesthetically.