How To Finish A Foundation Wall

When you frame exterior basement walls, insulate with rigid insulation or fiberglass insulation

By the experts at The Family Handyman

From The Family Handyman Originally in How To Finish A Foundation Wall

About This Project

• Overview and Preparation

• See an Illustration of a Wall With 2x2 Furring Strips and Foam

• See More Basement Projects
  

A   We’ll assume that you have either a poured concrete or a cement block masonry wall. With either surface, the finishing options are the same.

Before beginning any work, you must determine whether your basement has any moisture problems. If your foundation walls are only damp on humid summer days, fine—you’re good to go with the methods we recommend. But if you have any problems with standing or leaking water in the spring or during heavy rains, you’ve got some “prework” to do.

Fixes usually are as simple as adding or repairing gutters and downspouts or adjusting the grade to direct runoff water away from the house. But serious water problems may call for drastic measures like interior or exterior drain tiling, or exterior waterproofing, which could mean digging around the house or tearing up part of the slab. You must solve all water problems, or you’ll risk boxing future water in behind a finished wall, ruining it. You’ll end up spending hundreds of bucks re-remodeling a recently finished lower level.

Just about every carpenter or building inspector has a different opinion on how to finish walls against masonry. The methods we’ll demonstrate work well in most conditions, but consult with your building inspector before beginning any work to make sure you’re meeting building codes in your area.

As you mentioned, there are two methods of finishing against masonry: fiberglass-insulated 2x4 walls and foam filled 2x2 walls. Both methods include a 3/4-in. foam moisture barrier between the framing and the foundation wall to eliminate condensation from interior humidity and to protect the walls from exterior moisture. Tack the foam to the foundation wall with a few blobs of foam construction adhesive to hold it while you frame the walls.

Method 1: A conventional wall

2x4 framing method

Fast to build, lots of room for wiring and plumbing

Gobbles up 38 sq. ft. of space in a 20 x 36-ft. basement

The easy finishing method is to simply frame conventional 2x4 stud walls with pressure treated bottom plates (the 2x4s the wall rests on) and fill the walls with fiberglass insulation. Hands down, it’s the way to go—if you have oodles of space in the room you’re finishing. Two-by-four walls are quick to install and there’s plenty of space for electrical work. Plus, you don’t have to hassle with fastening furring strips to concrete, and it’s easier to cut fiberglass insulation than to fit foam. The downside is that each wall steals nearly 6 in. of floor space from the perimeter of the room.

Note that the wall pictured above is pushed against the foam and then anchored to the slab with concrete screws and to the ceiling with 3-in. drywall screws. Don’t install a vapor barrier between the fiberglass and drywall because moisture will be trapped in the wall.

Method 2: 2x2 furring strips and foam

2x2 furring strip method

Space efficient

Electrical installation is tougher

The downside is that electrical outlets and switches have special installation requirements. Cables must be at least 1-1/4 in. behind the front of the wood framing to prevent fasteners from accidentally piercing and damaging the cable. Use 1-1/4 in. deep steel boxes and run cable through EMT (electrical metallic tubing) between the furring strips to the boxes. Boxes and conduit straps are screwed through the foam and into the masonry with 1-1/2 in. concrete screws.