Walls, floors and insulation
What goes against the wall, and under your feet
The wall and the floor are where basements fail. We test them first, then choose what goes on them.
A damp basement can still be finished if the wall is allowed to dry toward the room. Closed-cell foam against the block stops vapor, and a stud wall in front holds wiring. Under the floor, a dimpled membrane and a subfloor leave an air gap, so a little vapor does not get trapped.
What a wall and a floor include
Foam board or sprayed closed-cell foam against the block, where the test calls for it
A stud wall set off the masonry, with the wires in front of the foam
A dimpled membrane and a subfloor, or a vinyl plank floor that tolerates moisture
Rim joists sealed and insulated, where they meet the wall
A dehumidifier line and a drain, if the logger says the air needs one
The price
What moves the price of walls and floors
What you put on them, and how damp they are.
Foam or batts
Closed-cell foam costs more than fiberglass batts and does more in a damp wall.
The test result
A damp result adds a vapor plan. A dry one may not need it.
Floor type
Vinyl plank over a membrane costs less than carpet over a subfloor.
Height lost
A subfloor and a drop ceiling take about three inches from the room height.
The slab
A cracked or uneven slab needs patching or a leveling coat.
Rim joists
Sealing the rim adds a day and saves heat.
The schedule
How walls and floors go
Two to three weeks for a 900-square-foot basement, in the first half of a finish.
- 01Week 2
Step 1: Prep
Walls are cleaned and cracks are patched. Any outside source is fixed first.
- 02Weeks 3 to 4
Step 2: Foam and frame
Foam goes against the block. The stud wall goes up in front.
- 03Weeks 7 to 8
Step 3: Floor
Membrane, subfloor and the finish floor, once drywall is done.
Permits
Permits for walls and floors
Insulation and flooring do not need a permit on their own. They are part of the finish permit, and the inspector checks the insulation and framing before drywall.
Questions
Before you book
Can you insulate a damp wall?
We don't finish over a wall the test calls wet. A damp wall can take foam, and a dry wall can take less.
What about mold?
If we find mold on the wall, we stop and tell you. A mold cleanup is a separate job for a company that does it, and we start again afterward.
Will the floor be cold?
A subfloor and a membrane help. In-floor heat is possible, and we plan for it before the floor goes in.
Wall or floor question?
Send a photo and we will tell you what the test will look at.