Testimonial : 

I am finishing a room in the basement, and I have a concrete ledge that is part of the foundation. It protrudes about 5 cm into the room and is about 15 cm high. This protrusion results from a particular way of laying the foundation, which leads (I am told) to higher ceilings in the basement, but leaves this protrusion rather awkward.

There are several ways to solve this problem, as I learned from looking at similar homes in my area: some frame the walls completely inside the ledge, reducing the finished room by that much; others frame the walls at the height of the windowsill and create a shelf in the room at that height.

I decided to maximize the room’s space and finish the walls above the eaves, intending to create an exaggerated baseboard around the concrete cornice. However, exactly how to do this proved to be complicated.

First, the thickness of the concrete (which protrudes into the room) is not uniform. It is 5 cm in the middle but almost 5 cm at one end and 5 cm at the other. Whatever covers it will have to compensate for this discrepancy. The height of 6 inches is fairly constant.

Also, the concrete could be smoother; many small protrusions will need to be worked around or removed with a chisel or hammer.

Finally, I would like some insulation to keep the room from the cold concrete.

Concrete Ledge in Garage

So I have two ideas that might work:

A. Use glue to attach the 1/2 thick foam insulation to the top and sides of the eaves. Next, attach the MDF to these surfaces with glue and round the corners with a router. Next, apply a coat of primer and paint.

B. Cut 2x4s between 1/2 and 3/4 inch thick and fasten them to the eave surface every 16 inches, using cement anchors. The thickness of the 2x4s will vary so that the final result is square to the room and compensates for the irregular shape of the concrete. Attach the MDF to these elements. Fill the air spaces with expanding foam insulation. Finish the MDF with a milled corner, primer, and paint.

Is a better or generally accepted way to build around these concrete ledges? In short: is there a way to build around a concrete ledge?

Facts that may or may not be important:

• The basement is at ground level.
• The room measures 11 feet by 9.5 feet (105 square feet). The ledge is only on the two outer sides.
• The floor will be laminate.
• The existing walls are insulated, framed, and finished with primed, textured drywall.

What is a concrete cornice?

A cornice is a reinforced concrete support that supports the weight (100 kg per square meter or more) of finished materials such as brick, stone, or other cladding, working directly on a baseboard or other foundation element. Typically, brick or stone cladding is placed on the exterior for a home improvement.

How to finish a room with a concrete cornice over the foundation?

The first solution is to frame the walls inside the cornice. This is the easiest and fastest solution. The second solution is to build two walls, one above the cornice, placed as far back as possible, and one in front of the cornice. Finally, a “cap” should be built over the cornice when the work is finished.

How to clad the concrete walls of the garage?

The most reliable way to cover concrete walls is to use wood to make a wooden structure that rests directly on the concrete. This wooden structure can be used as a foundation. The simplest method is to place drywall on top of this structure and use paint to give it the desired look.

How deep should the garage foundation be?

In most areas of the United States, garage foundations are usually dug 36 inches below finished ground. Foundation dimensions are usually 20 inches wide and 8 inches deep. If your municipality requires something different, follow its requirements.

What is the purpose of a cornice?

A cornice is an overhang on a wall. Its function is usually to direct rain away from walls and windows. In addition, they are often designed to improve the aesthetic appearance of a building.

How do I attach a cornice to a concrete foundation?

Use a wood drill bit to drill ½” pilot holes through the cornice. Then use a concrete drill bit to drill through the concrete wall. Install two screws at the end of each cornice. Drive the anchor sleeve through the fascia into the concrete wall.