Introduction: A basement room addition is a great idea to expand the living space of your home but they can be difficult to heat if the floor is not insulated. When planning to build a basement room install basement floor insulation. Sure, this will drive up the cost but it will save you the frustration of trying to heat the room and be comfortable in it.

A concrete basement floor draws the cold from the outside through the basement walls and the ground below the basement floor. Ideally the floor should be insulated during the basement construction however, most builders do not go through the expense unless the homeowner specifically requests that the floor be insulated. Most DIY homeowners perform finished basement projects themselves. Building a floor on top of concrete and insulating the floor should be the first step in the process of building a basement room.

Material required:

Pressure treated 2x4s
Construction glue (liquid nail)
Concrete nails
1 ½ inch polyurethane insulation board
¾ inch tongue and groove plywood subfloor
Subfloor screws
Tyvek tape

Installing the floor:

Clean the floor by sweeping and vacuum the area thoroughly before starting. Next measure off the wall 2' and make a mark. Repeat this all the way down the wall. Repeat again in 2' increments. Snap chalk lines along the marks. This will provide a straight guild to lay down your treated 2x4's.
Lay down pressure treated 2x4s along the lines and around the perimeter. Use liquid nail adhesive between the 2x4s and the concrete. Drill 1/4" holes through the 2x4s and into the concrete. Use concrete nails to attach the 2x4s to the concrete. Nails should be placed approximately every 3 feet.
Cut the 11/2" polyurethane foam board insulation pieces to fit using the next 2x4s. A utility knife will cut the foam board. Make sure the foam board fits tight in-between the 2x4s. Tape all seams with Tyvek tape.
Apply liquid nail to the 2x4s. Screw the 3/4 inch sub-floor plywood to the 2x4s with 1 5/8" screws every 6 inches. Stagger the seams of the flooring sheets to prevent buckling.
Now that the sub floor is installed you can install any kind of floor finish.

Basement wall insulation is just as important as insulating the basement floor. I recommend that you insulate the walls with 1 ½ inch polyurethane insulation board, using the same technique as you did insulating the floor.

Framing A Finished Basement

Foundation Drainage System

Insulating Finished Basements

Painting Basement Concrete Walls