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Is Spray Foam Insulation Waterproof? (Read This First!)

When it comes to insulating your home and making it energy efficient, spray foams are one of the best materials you can use. But can you seal a crack with spray foam? Is it waterproof? 

We will discuss the water-resistance of different types of foam insulation and some related facts you should know.

Is spray foam insulation waterproof?

Some spray foam insulations are waterproof, while others are not. Specifically, the closed-cell spray foams are waterproof, and open-cell spray foams are not waterproof. The water resistance depends on the molecular density of the spray foam insulators. 

There are different types of spray foam insulation available in the market, so it’s confusing to understand the specific nature of spray foam. Different types of spray foam have distinct characteristics and water resistance.

There are two basic types of spray foam insulators. As we mentioned earlier, one is open-cell spray foams, and the other is closed-cell spray foams.

Open-cell spray foams expand more, and they have a lower density. As a result, open-cell spray foams are full of tiny holes that can absorb water. It is also deficient in weight due to its low molecular density.

Closed-cell spray insulators are compactly bonded together. It expands more minorly than the open cell insulators. The molecules of closed-cell insulators stay close to each other; as a result, the surface can resist water.

Open-cell insulators are cheaper and more cost-effective between the two types. Closed-cell insulators are better for insulation, toughness, and fire and water resistance.

However, open and closed cell insulators are defenseless against fire (like all the plastic material), although they can resist two times more than the open cell insulators due to their molecular structures.

If there is a moisture problem in your home, closed-cell spray foams are better. Open-cell spray foams absorb moisture and lead to high humidity and energy loss.

Check out if the listed spray foam can resist moisture.

Polyurethane spray foam:

Polyurethane spray foams are water-resistant. It is a spray form of polyurethane and is widely used in insulating houses and sealing different types of cracks.

Expandable spray foam:

Some expandable spray foams are water-resistant, and other spray foams are not. All types of spray foams expand, and the closed-cell spray foams can resist water while open-cell spray foam can’t.

Loctite spray foam:

Loctite Spray foams are resistant to moisture and very durable. It can be used to seal cracks and water.

Eastern Iowa spray foam:

Eastern Iowa spray foam does not soak in water, so you can use it for waterproofing purposes.

High density closed cell spray foam:

High-density spray foams can resist water due to their dense molecular structure. It is also called closed cell spray foam insulation.

Open-cell spray foam:

Open-cell spray foam can not resist moisture, although it can dry in a few days, depending on environmental conditions.

Is spray foam insulation water-resistant? Can spray foam insulation get wet?

There are many water-resistant spray foams in the market. You can also find non-water-resistant spray foam too. Before buying or getting a spray foam service, make sure you know enough about the spray foam you are getting.

If you have closed-cell spray foam, you can use it for waterproofing purposes, but open-cell spray foam can not resist water. Ask your service provider to get all the information about the spray foam.

When open-cell spray foam gets wet, it becomes heavy and sometimes changes its shape if thoroughly soaked in the water. But like most objects, it gets dry with time.

Depending on the airflow and ventilation, the drying time can be two to seven days.

You can find canned spray foam in the market. Those spray foams are used to seal cracks and holes. However, you can not apply spray foam in your house to insulate it alone. A professional team has the necessary experience and tools to use it ideally.

Can spray foam stop water leaks?

Most spray foams can stop water leaks from cracks. Closed-cell spray foams work better than open-cell spray foam. But both are used to seal gaps that leak water.

Open-cell spray foams are not water-resistant in normal conditions, but the molecules expand inside the gap when directly sprayed in a crack. It can not expand as much as it can in an open place. So, technically it becomes a high-density foam that can resist water.

But if you want the best option to seal a leak, closed cells or especially polyethylene foam spray is the best. Polyethylene can naturally resist water in average conditions.

Before you get the spray foam service, find out the cracks or breakage of your house. Once the insulator is installed, any leakage on your roof can cause a mess in the rainy season (if you use an open-cell insulator).

Open-cell insulator does get wet, but it can resist mold or bacteria buildup in the foam part. A damp foam can lead to temperature loss and high humidity. However, a wet foam gets dry within a few days.

What happens when spray foam insulation gets wet?

Here’s what happens when spray foam gets wet.

Absorbs water:

Closed-cell spray foams are not super water-absorbent like the foam inside your sofa. But it can absorb a lot of water if it stays in contact for long. It also can absorb moisture from the air.

High-density foams do not absorb water when they get wet. Those are the best choices if you have a moisture problem in your house.


When low-density spray foam gets wet for a long time, it can deform. That can be problematic in high-moisture conditions. But it usually does not happen without flood. 

However, some companies claim that their spray foam does not bend in the presence of water.

Lose energy:

If you install low-density spray foam in your house and it gets wet. It can lead to temperature loss in your home. However, damp spray foam becomes dey within some days.

Increase humidity/ mold:

Wet spray foam resists mold but increases humidity. As a result, molds can grow in other parts of your house.

The foam has no energy source, so any mold, fungus, or bacteria can not grow over it. Although if a nutritious liquid falls over low-density foam, other organisms can grow.

Does water damage spray foam?

Yes, water can damage some spray foams. Cheaper spray foams are less hardy and can get affected by water and weather. Open-cell spray foams can absorb moisture and can shrink. However, good-quality closed-cell foams should not shrink in the presence of water.

Closed-cell spray foams can resist water and almost gets no damage. When it floods, foams that absorb water can get back to their original shape within about a week.

But the problem is, floodwater can contain various pathogens that the foam can soak. So it is better to change the foam after the flood.

It’s not a good idea to use open-cell spray foam on the roof. If the roof leaks, the foam will constantly contact water and deform easily. You can use close cell spray foam on the top.

What type of spray foam is waterproof?

If you are looking for waterproof spray foam, here is a list of water-resistant spray foam.

High-density spray foam:

High-density spray foams are a type of closed-cell spray foam that is highly resistant to water. It is the most expensive spray foam in the market and costly too.

High-density spray foam can also resist wind and ultra violate rays.

Medium density spray foam:

Medium-density spray foams are commonly used in most places. It can resist water but a bit less than high-density spray foams. You can also use it to make a room soundproof.

Hybrid spray foam:

Hybrid spray foams are a combination of high and low-density spray foams. The manufacturers claim it to be water-resistant. Follow the manufacturers’ guide before using it.

Polyurethane spray foam:

Polyurethane spray foams can resist water effectively. It is tougher than usual spray foam insulators. You can also use it to seal cracks. A good-quality polyurethane spray foam insulator can be highly resistant to water and weather.

Final thoughts

Not all spray foams are waterproof. So if you have a moisture problem or aim to make something waterproof, you should get high-density spray foam that can resist water comfortably. However, you will have to pay a bit more to buy waterproof spray foams.