How To Fill Void Under Bathtub (Explained)

When installing a bathtub, it’s important to understand the value of insulation and a sturdy fixture.

Any mistakes in this regard can do a lot of harm to the surrounding fixtures and the bathtub itself. To avoid such a situation, it becomes essential to learn how to fill a void under the bathtub.

To fill the void under a bathtub, start by measuring the space. Now cut foam insulation pieces to fill at least half of the void. Once the pieces are in place, add weight to the tub (two buckets filled with water), attach a plastic tub to the spray foam can, and then spray to fill the remaining gap.

This process does not take a long time but it’s important to measure everything. You don’t want a little bit of space to be leftover during the process.

Be detailed with the spray foam and make sure to cover the void properly.

This guide will explain how to fill a void under the bathtub and what mistakes to avoid during the process.

Best Foam For Bathtub (EDITOR’S CHOICE)

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Steps To Follow On How To Fill Void Under Bathtub

1. Measure Space Under The Bathtub

When finding out how to support a bathtub, you will want to consider filling the void using expanding foam.

To fill the void under a bathtub using expanding foam, it’s important to begin with the basics including the measurements.

How big is the void? How much expanding foam will be required?

These questions are important when you are planning the project. Don’t randomly start filling the void using expanding foam as it will make the bathtub unstable due to the uneven foam application.

Be thorough when measuring and consider the depth of the void.

how to fill void under bathtub

2. Set Up Foam Board Insulation

Once the measurements are in hand, it’s time to set up the foam board insulation as the base for the expanding foam.

You will want to go out and buy quality foam board insulation.

Once you do that, look to fill 50% of the void using these boards. You can stack them on top of each other to get the desired result.

3. Add Weight Inside The Bathtub

Using expanding foam under the bathtub is a wonderful idea, but you will want to consider the weight being put inside the tub too.

You have to recreate this by putting weight inside during the process.

How do you do this?

Just take 2-3 buckets of water and put them in the tub while applying the foam. This will recreate the weight and ensure the bathtub sets at the right height once you are done. This is key for sustainable stability.

how to fill void under bathtub

4. Hook Plastic Tubing To End Of Spray Foam Can

You will now begin to work on prepping the spray foam.

The expanding foam is going to come in a spray can. You will want to hook up a spray gun or a plastic tub to make the application process ten times easier.

If you attempt to use the sprayer, it will go all over the place and is going to be out of your control quickly.

Use plastic tubing if you don’t want to go out and buy a spray gun. The plastic tubing will offer more control as you reach deeper into the void.

5. Spray Foam To Fill Void Under Bathtub

The last step is to complete the task.

Just begin spraying the expanding foam under the bathtub. Fill the gap that is still leftover above the foam insulation boards.

Go from one end to the other and make sure to not miss a spot. The goal is to create a well-balanced base for the bathtub to sit on.

This is where the expanding foam is going to do its job.

Final Thoughts

Follow these steps on how to fill a void under the bathtub correctly.

To fill a void under the bathtub, it’s important to measure the space beforehand. With these measurements, cut out foam insulation boards. Fill 50% of the void using these boards. Once the boards are in place, add two buckets filled with water into the tub for weight, connect plastic tubing to the spray can, and begin filling the remaining void using the foam.

It’s a simple process that has to be done with a lot of care.

If you follow the steps cited here, the expanding foam under the tub will work like a charm and create a strong base.

This is what competent insulation is all about.

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