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Spray Foam Basement Walls: How to Do it for Your Home



V Susan
Hi! I'm Susan. I am passionate about woodworking, general DIY and home improvement. If you'd like to connect with me or talk about something you like at mellowpine, drop me a mail at susan@mellowpine.com


Spray Foam Basement Walls

Spray foam insulation is an excellent choice for basements. It effectively creates a watertight and airtight barrier by serving as a monolithic seal between the foundation wall and the frame. With a lifespan of 80-100 years, spray foam insulation is a long-term solution for protecting one’s basement.

How to Spray Foam Basement Walls?

How to Spray Foam Basement Walls?
How to Spray Foam Basement Walls?

Before we go into the step-by-step process, it is essential to note that applying spray foam involves using potentially harmful chemicals. 

Consult a professional to ensure proper application and reduce the probability of injury.  

Here’s a step-by-step guide on spray foam installation.

Step 1: Be Well Equipped

The first step is to equip yourself with protective gear.

A full-body protective suit, a respirator, and a set of sturdy shoes and gloves are essential.

Step 2: Test the Moisture Levels of the Surfaces to be Treated

Moisture Meter
Moisture Meter

Foam cannot stick to wet surfaces.

Chances are it will slide right off or have cavities or holes. 

Spray foam generates the best results when applied on surfaces with less than 20% moisture level. 

Test the moisture levels of the desired application surface using a moisture meter. 

Step 3: Formulate a Plan of Application

Prepare an application strategy before spraying.

Determine which surface you will treat first and check if you need a ladder to reach all parts of the surface.

Also, determine a spraying pattern, whether to spray from left to right or down to up. 

Once you decide on your plan and pattern, it is crucial to understand your equipment. 

When you stop spraying the foam for over 30 seconds, it will start curing and solidifying inside the nozzle and clog it. 

Now, you will have to replace the nozzle.

You can find multiple nozzles inside your kit; be sure to keep them ready. 

Set your equipment according to the instructions provided by the manufacturer, and do a test spray inside a disposable box. 

Be wary of the fumes; open a window or set up a fan to vent them.

Step 4: Spray the Frame First

Once the equipment is set up and tested, you can commence spraying.

The correct way to spray foam on a panel is to spray it on its frame.

Spray the frame or the four sides of the panel with a ½ inch thick layer.

This layer will then swell up to a thickness of 1 inch. 

By doing this, you will be ensuring a proper seal between the frame and the foam.

This will reduce the possibility of any leftover cavities and will also reduce the possibility of bulges. 

Step 5: Spray the Remaining Portion

After applying the foam on the edges, wait a few minutes for the foam to swell a bit. 

Replace your nozzle and spray a 1-inch thick layer of foam on the remaining portion of the panel. 

Wait a few minutes for the foam to swell up, then spray another 1-inch thick layer onto the entire panel after letting the foam cure. 

In total, you should have applied a 2-inch thick layer to the panel.

These layers will swell up after a few minutes. 

After spraying foam on all the desired surfaces, leave it to cure for at least 8 hours. 

Upon returning, you will find the foam to have solidified and covered the entirety of the panel.

Step 6: Remove any Overspray

Excess material may be found present on the frame of the panel and in the near vicinity. 

Using scraping tools, trim any excess foam from the frames and the panel. 

This step is important as allowing excess foam on the panel’s surface may create hindrances while setting up the dry walls.

Why Should You Spray Foam Your Basement Walls? 

Why Should You Spray Foam Basement Walls?
Why Should You Spray Foam Basement Walls?

Spray foam insulation can provide a lifetime’s worth of protection for your basement. 

Mold is a threat to basements’ structural integrity and serviceability.

It usually grows best in moisture-rich environments. 

Spray foam creates an environment resistant to mold growth and effectively keeps basements safe.

Applying spray foam also reduces the heat transfer to almost 50%, effectively reducing the energy consumed in heating the basement and, in turn, helps save money. 

Moreover, spray foam, when applied on the basement exterior walls, results in the walls having a changed dew point; this reduces condensation on the basement walls. 

Different Types of Spray Foam, Which One is Better? 

Two different types of spray foam are available commercially. 

Open-cell and closed-cell spray foam have the same function, but each has unique characteristics. 

It is up to the energy consultant and the homeowner to determine the best that suits the structure’s needs.

Here is a table displaying the differences between the two types:

PropertyOpen CellClosed Cell
Cell EncapsulationPartially encapsulated Fully encapsulated
RigiditySoft and flexibleHard and rigid
Density0.5 lbm/ft31.75 lbm/ft3
ExpansionExpands up to 3 inchesExpands up to 1 inch
R-ValueR 3.6 to R 3.9 per inch,
Less insulation capacity
R 6 to R 7 per inch,
Better insulating capacity
Different Types of Spray Foam

It is difficult to determine which type is superior; both have advantages and limitations. 

Closed cells are completely closed, as opposed to open-cell spray foams, which are left open.

Their R-values are higher, so they provide better insulation and moisture resistance.

Open-cell spray foam has superior expansive properties.

It can reach the nooks and crannies of the entire basement. 

Open foam also provides better sound insulation when compared to closed foam, but it falls short in protecting against moisture and mold growth. 

However, closed cell is more expensive than open cell spray foam. 

Considering these factors in mind, it is impossible to claim one type to be better than the other.

But you can make a suggestion.

Opting for closed-cell spray foam is wise if you reside in extreme environments. 

The added protection against moisture and the ability to create a heat seal may prove to be invaluable and economical in the long run. 

However, professionals recommend open-cell spray in areas where the weather is not extreme. 

Open-cell spray foam can easily resist moderate temperatures and low moisture levels in the air.

Cost of Spray Foaming the Basement Walls

The average cost of spray foam insulation falls around $1,200 to $3,500, with the national average being $2,500.

Various factors come under consideration when calculating the cost of spray foaming a basement. 

A significant factor, among them, is the total area of treatment, as it will determine the amount of material consumption. 

The thickness of the foam layer applied is also important.

Usually, the layer will be either 1, 1.5, 2, or 3 inches thick.

Another factor is location.

If you reside in a town with limited manpower available, the cost of spray foam may rise. 

Lastly, the type of foam used, open cell or closed cell, also matters.

Open-cell spray foam normally costs $0.44 to $0.65 per square foot, while closed-cell foam costs $1.00 to $1.50. 

The R-value of Spray Foam Insulation

Understanding the R-value is key to gauging different insulation materials with each other. 

An R-value measures the resistance of a material to heat transfer; a higher value indicates greater heat resistance.

Spray foam is an excellent conserver of heat; this means that spray foam’s R-value is bound to be high. 

The R-value of open cell spray foam ranges from R-3.6 to R-3.9 per inch, while closed cell foam has an R-value of R-6 to R-7.

Thickness of Spray Foam Insulation

Thickness of Spray Foam Insulation
Thickness of Spray Foam Insulation

The spray foam’s thickness depends on the foam type used. 

Closed cell spray foam usually expands to about a thickness of 1 or 1 ½ inches.

On the other hand, open-cell spray foam expands up to an astounding 3 inches in thickness.  

Does Spray Foam Insulation Require a Vapor Barrier?

IRC 2021 has provided guidelines as to when and where is the use of a vapor barrier permitted.

A vapor barrier is a seal that resists water vapor penetration. 

The IRC deems the need for a vapor retarder or barrier according to the climate. 

According to the guidelines, areas under Climate Zones 1, 2, and 3 do not need a vapor barrier.

Zones 4, 5, 6, 7, and 8 may need one, but it depends on case to case. 

If you opt for spray foam insulation, specifically closed cell spray foam, you do not necessarily need to provide a vapor barrier as the foam acts as one. 

In contrast, open-cell spray foam needs one, as it may not create a moisture barrier. 

Consider hiring a professional consultant to determine the spray foam best suited for your basement and whether there is a need for a vapor barrier.

Spray Foam Insulation: Advantages and Disadvantages

The advantages of spray foam include the following:

  • One of the most efficient and effective methods of insulation available commercially. 
  • Reduces heat loss to approximately 50%, aiding energy savings and utility bills. 
  • Spray foam’s expansive property allows it to create an air seal. 
  • Reduces the growth of molds. 
  • Makes the structure highly resistant to water damage.
  • Has a life span of 80-100 years.
  • Provides additional load-bearing strength to the walls.
  • Has a stable R-value throughout its life cycle.
  • Spray foam is eco-friendly. 

Some of the disadvantages of spray foam are:

  • Installation costs are high.
  • Requires experienced manpower for installation.
  • Can create risks to human life 
  • Needs time to cure. 
  • It can shrink over time upon improper application. 
  • Not capable of filling every hole or cavity. 

Spray Foam vs Foam Board vs Fiberglass

Spray Foam vs Foam Board vs Fiberglass
Spray Foam vs Foam Board vs Fiberglass

All three of them are effective methods of insulation.

Spray foam, as mentioned earlier, is a type of insulation that involves spraying a mix of two chemicals onto a surface. 

The foam then swells up and, after providing it a certain amount of time to cure, it will harden.

On the other hand, foam boards are panels of specific sizes made of insulating foam. 

Typically found in 2’x8′ or 4’x8′, foam boards are easy to install and convenient for large or small basements. 

Fiberglass insulation is one of the most commonly used insulation techniques, made from molten glass.

Preferred for their ease of application and customizability, you can find fiberglass insulation in spools or rolls. 

PropertySpray FoamFoam BoardFiberglass
FormAvailable in canistersAvailable in foam or rigid panelsAvailable in loose rolls or panels
R-ValueR 6-R 7 per inchR 4-R 6.5 per inchR 2.2-R 3.8 per inch
CostExorbitantSlightly expensiveCheap
ApplicationCan insulate interior and exterior wallsCan insulate exterior wallsCan insulate interior walls
Moisture ResistanceVery HighHighMediocre
InstallationComplex installation processEasy installation processEasy installation process
Life Span80-100 years80-100 years5-7 years
Fire HazardFlammable under certain conditionsFlammable under certain conditionsFire resistant
Sound ProtectionGreat protectionGood protectionPartial protection
Spray Foam vs Foam Board vs Fiberglass

Is Spray Foam Insulation Capable of Waterproofing a Basement?

Spray foam is an insulation technique; it may be able to keep the water out, but it cannot protect against it. 

It does seal any cracks due to its expansive properties but can do more harm than good. 

The foam will stop any water from entering your basement by sealing any cracks and cavities, but it will force the water to build up and form a pool. 

Eventually, this pool of water finds another way in, and while doing that, it’ll force the wooden and steel members to rot quickly. 

Thus, prolonged exposure to water may even reduce the structure’s stability. 

Applying other waterproofing methods over spray foam insulation will provide adequate protection for your basement.

Frequently Asked Questions

Is it Acceptable to Leave Spray Foam Insulation Exposed in a Basement?

Spray foam is made up of plastic.

Plastic is flammable, and that means spray foam is too. 

According to IRC 2021, it is necessary to install a 15-minute thermal barrier onto walls with spray foam to reduce its flammability.

Does Spray Foam Work on Concrete Basement Walls? 

Spray foam is applicable on almost any surface, regardless of the material of the wall. 

If applied, it will be an effective insulation technique on concrete walls.

Is it Possible to Add Spray Foam Insulation on Your Own?

Many experienced DIY enthusiasts can install spray foam insulation independently, but hiring a consultant is better. 

Due to its high cost and complex installation procedure and to avoid errors, it is best if you take the help of a professional to install spray foam insulation.

V Susan
Hi! I'm Susan. I am passionate about woodworking, general DIY and home improvement. If you'd like to connect with me or talk about something you like at mellowpine, drop me a mail at susan@mellowpine.com