How to Build a Room Addition and Expand Your Living Space

Every large remodeling project needs to start with a plan. Many homeowners choose to hire the help of a local architect or a design-build contractor before making any plans. Here’s what to do.

Create several drawings, including a floor plan and interior and exterior elevation plans.

Submit those drawings and an application at your local permitting office so you can obtain a building permit and, if necessary, other needed permits.

You’ll also need to call 811 to have your utility companies perform an underground survey.

Your builder (or foundation contractor, if you’re acting as your own contractor), will bring in some heavy equipment for this step.

Dig a hole to accommodate the frost-depth footing or concrete slab, and pour the concrete foundation or slab. Install concrete blocks onto the new foundation, if necessary. Then, have the inspector sign off on the foundation.

Speed is your friend during this step to make the project weather-tight and avoid water damage that can happen during delays.

Install the floor joists and subfloor sheeting. Frame the exterior walls, the roof rafters, and install roof trusses. Cover the exterior of the walls and roof framing with sheeting (plywood or other similar material).

Next, install roofing shingles or other roofing material, and an exterior moisture barrier and seal with sealing tape. Add windows and an exterior door, if they’re part of the plan.

Have the inspector perform a framing inspection. Install exterior siding at any time after the previous steps.

Your room addition needs electrical and HVAC components, and depending on the addition, you may need plumbing as well.

Install heating and cooling ductwork and the rough-in plumbing, if necessary. Put electrical wiring in place last behind the first two mechanical systems. Have the inspector perform rough-in mechanical inspections.

Insulation is a requirement in every living-space addition. To install it, use spray foam insulation or install batt insulation below the roof rafters. Also use spray foam insulation or install batt insulation into exterior wall cavities.

Create a vapor barrier envelope with plastic sheeting, sealing tape, and caulk throughout the room, then have an inspector give the OK.

Now it’s starting to look like a room. Install drywall on the ceiling and walls. Finish the drywall by mudding it, and then give it a coat of paint.

Now, the mechanical technicians can return to complete their work.

They should install any HVAC components such as duct grilles or radiant heaters. If plumbing is part of the project, install the plumbing fixtures now. Put electrical outlets, switches, covers, and lighting components in place.

This part always seems to take the longest out of the sheer anticipation of getting to use your new room.

Install the flooring material. If you plan on having carpeted floors, this step can wait until after the trim work step. Set the interior door or doors. Apply a coat of finish to the trim boards and install the trim work. Apply a final coat of finish to the trim.

Call the inspector to perform the final inspection and sign off on the project as complete.