How To Cover Rigid Insulation On Foundation Walls?

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Are you planning to insulate your basement, and you aren’t sure how to cover the insulation afterward? You’ve come to the right place because we’ve researched this question, and we have the answer for you.

Furring can be installed over the rigid foam board then gypsum boards are screwed through the furring. If the rigid foam board is too thick for screws, the gypsum board can be fastened using foam board adhesive.

These are the summarized steps to install rigid foam covering. We will talk about these steps in more detail in the succeeding sections.

Read on!

Technician installing rigid foam insulation on the exterior wall, How To Cover Rigid Insulation On Foundation Walls?

How To Cover Rigid Insulation On Foundation Walls?

Before we proceed to the installation of covering for your rigid insulation, here are some things to keep in mind when covering rigid insulation for foundation walls.

Moisture drying

Foundation walls—in part or whole—cannot dry on the exterior side because it is below grade (it means that it is below ground level).

Part of covering rigid foam insulation on foundation walls is making sure that the foundation wall will be able to dry from the interior side. This includes installing insulation that is semi-permeable to allow moisture on the foundation wall to dry.

Rigid foam R-value

Different types of insulation on top of a house plan

Make sure to check the total R-value of your installed rigid foam boards before covering them. It will be difficult to add insulation after you cover the rigid foam.

You can install multiple rigid foam insulation on top of each other if they are not faced. Installing faced rigid foam creates an area that can trap moisture and promote mold growth.

How to cover rigid foam board insulation with notched edges on foundation walls?

Here are the simple steps to cover insulation on foundation walls:

  1. If you used a rigid foam board with a notched edge, each pair of rigid foam boards will create a channel between where you can fit in a narrow furring strip. Use a hammer drill with a carbide-tipped steel drill bit to drill a hole through the rigid foam board all the way to the foundation wall.
  2. Position the furring strip over the channel between two rigid foam boards. Fasten it on the wall using a concrete screw anchor. The furring strip helps keep the rigid foam board in place.
  3. Apply a screw every 2 feet of length.
  4. Get small scraps of wood and measure half an inch of thickness. Trim the scraps of wood until you have enough to support the drywall.
  5. Place the scraps of wood on the floor where it touches the rigid foam insulation. Make sure that they are placed at the same height.
  6. Place the gypsum board on top of the scraps of wood on the floor and press it against the insulation.
  7. Fasten the gypsum board on the furring using screws.
  8. Remove the scraps of wood under the gypsum board.
  9. Seal the entry point of the screws with caulk.
  10. Seal the exposed seams of the gypsum board except for the bottom.
  11. Complete the installation with your chosen finish.

A set of 10 chrome-plated masonry drill bits from Owl Tools with industrial-strength carbide tips is available on Amazon. Check it out through this link.

Why elevate the gypsum board?

Worker applying plaster on the holes of the gypsum board

Elevating the gypsum board creates a small opening at the bottom where moisture from the foundation wall can escape. This will allow the foundation wall to dry on the interior side and prevent moisture from accumulating on the wall and insulation.

This is also the reason why it is important to use a semi-permeable rigid foam board to insulate the foundation wall. Semi-permeable rigid foam insulation will allow moisture to pass through to escape from the foundation wall to your basement to dry.

It is important to place this gap only at the bottom of the gypsum board because the warm air of the basement will tend to move up as per the law of thermodynamics.

This prevents the warm air of the basement from escaping to the foundation wall and creating condensation there.

How to cover rigid foam board insulation without notched edges on foundation walls?

Installing gypsum board to cover non-notched rigid foam board insulation is similar to installing gypsum board for notched rigid foam board insulation.

Follow the steps below to install a gypsum board to cover the non-notched rigid foam board insulation.

  1. Cut wood scraps that are half an inch high and position them on the floor where you will install the gypsum board.
  2. Determine the thickness of the rigid foam board.
    • If the rigid foam board is not too thick, drill a hole through the rigid foam board up to at least half an inch on the foundation wall.
    • If the rigid foam board is too thick to have a screw penetrate its thickness with at least half an inch more to penetrate the wall, then use foam board adhesive instead. Spread an even layer of foam board adhesive on one side of the gypsum board.
  1. Place the gypsum board on top of the wood scraps and press it on the rigid foam board.
    • Fasten the gypsum board using a concrete fastener screw. Install a screw every 12 to 16 inches.
    • Wait until the foam board adhesive is dry enough before letting it go.
  1. Repeat steps 2 and 3 until you have installed the gypsum board over all the rigid foam board insulation on the foundation wall. Apply caulk to seal the screw entry points.
  2. Complete the installation with your chosen finish.

Sealing the sill plate

  1. Seal the corners of the sill plate, subfloor, and floor joists with canned spray foam. Do the same thing with the top of the gypsum board and the rigid foam board.
  2. Let the spray foam expand, harden, and dry overnight.
  3. Trim any excess spray foam with a cardboard cutter.
  4. Check for any gaps in the seal and reseal them with the canned spray foam.

The 12-ounce can Loctite TITE FOAM insulating foam sealant is available on Amazon. Check it out through this link.

What kind of wood do you use for furring strips?

Technician installing rigid foam insulation on the exterior wall

Furring strips are used to fill the channel created by the notches in the rigid foam board, and you might be wondering what they are made of.

Furring strips are often made from pine or fir. Its main purpose is to provide a structure where drywall can be nailed to.

Can you leave rigid foam board exposed?

Some rigid foam insulations are fire-resistant, while some are not. A gypsum board helps counterbalance that by serving as a fire-resistant layer to cover the foam insulation that is not fire-resistant.

Should you put a vapor barrier on basement walls?

According to Today’s Homeowner, there are building codes that require the installation of a vapor barrier on the exterior basement walls if wooden framing will rest against the outer basement walls.

This is to prevent the moisture from the concrete foundation walls from getting absorbed into the wooden frames.

The wooden framing will rot if it is allowed to absorb moisture from the external walls.

Some basement designs counter this by installing the wooden wall framing with a space of at least 4 to 6 inches away from the external concrete wall. This is to prevent the wooden framing structure from absorbing moisture from the external basement wall.

It is normal for external basement walls to absorb moisture from the ground, especially after heavy rains.

What is the difference between a foundation and a foundation wall?

You might be wondering what the difference is between a foundation and a foundation wall. This is something that confuses most people.

The foundation serves as the legs of your house. It bears the weight of a house’s superstructure and transfers that to the ground.

If the foundation is the leg, then the footing is the feet underneath. It serves as a support for each individual column and the foundation.

Now, the foundation wall is a type of wall that is installed on the footing if you’re building a full basement foundation or a daylight basement foundation.

Instead of using several columns as a foundation, this type uses a thick layer of wall to support the structure of the house and serve as the foundation.

Crawlspace foundations also make use of a foundation wall, but they are much shorter than the foundation wall for the two examples above. They are typically 12 to 18 inches high only.

Conclusion

Technician installing rigid foam insulation on the exterior wall, How To Cover Rigid Insulation On Foundation Walls?

Covering the rigid foam insulation in your basement can be a simple project that you can DIY.

However, there are key considerations in installing a gypsum board, and one of the most important is to leave a moisture exhaust at the bottom of the gypsum board covering to allow the moisture from the foundation wall to escape and dry on the interior side.

If you enjoyed reading this article, why not check the two other articles below:

Is Styrofoam Insulation Waterproof?

How To Insulate Foundation Walls?

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