How to Insulate a Stone Foundation

Lead Image
  • 48-72 hours
  • Intermediate
  • 350-600
What You'll Need
Dry lumber
Grout bag
Insulation (2 layers)
Polyurethane air barrier
Vapor barrier

Many homeowners prefer a stone foundation for several reasons. It is the most common structural foundation of earlier houses or buildings; therefore, the materials used to make a stone foundation are easy to find and order. Stone foundations are also more durable than any other material. They are tougher than alternative materials.

They are less expensive to maintain, resulting in fewer long-term expenses. Stone foundations tend to be cold and damp, which leads to problems such as mildew and musty smells. Foundations made of stone also lose a significant amount of heat. For this reason, insulation is necessary for stone foundations.

There are three types of insulation: polyurethane spray, rigid plastic board, and blanket insulation. Spray insulation is the best option if your stone foundation is uneven and has moisture problems; however, it should only be applied by a professional. Rigid plastic board insulation is probably the strongest, but it is expensive. Whatever type of insulation you choose, estimate the total cost by checking with your local building supply dealer.

Step 1 - Assess the Situation

Before you begin, it is vital that you consider a number of factors which can affect how you insulate. Some of these factors include the type and condition of the wall, interior structure of the house, structural cracks or bulges, moisture problems, and finishing details. You must also consider if your area has problems with frost heave brought about by expansive clay soil. It is advisable to consult a local builder before applying insulation to your stone foundation.

Step 2 - Inspect the Walls

Check the walls you for moisture problems. Installing insulation will be easy if despite occasional dampness on the basement if you follow the correct procedures. If water leaks are frequent, make sure to repair the root cause of the problem before installing insulation. Use a polyethylene moisture barrier to cover the basement walls. It will also serve as a strong protection for the insulation.

Step 3 - Put a Wood Frame Wall in the Basement

There are two ways of framing the wall. You may use 2x4-inch lumber when installing the new wall flush to the old wall or use the same size of lumber which was built out from the wall itself. It is important to use dry lumber. If you are unsure about the lumber to use for framing, let it dry for about two weeks before installing it. Place the studs accurately with enough spacing in order to install the finish easily.

Step 4 - Install the Insulation

There are two layers of insulation to install. A horizontal layer between the walls and the studs should be installed first. Make sure to install it tightly against the wall. Then the vertical insulation, which is the second layer, should be installed accurately between the studs. Make sure there are no air spaces between the studs and the wall.

Step 5 - Install the Finishing

The finishing is usually composed of a vapor and polyethylene air barrier. They are placed over the insulation and the studs. Ensure that all the edges and penetrations are well sealed. Nail the surface of the finishing tightly against the insulation. Each joist ends should be air sealed to keep your stone foundation warm and dry.