How to Add a Garage on to a House

An attached garage is a big asset to your home.
An attached garage is a big asset to your home. (Image: brown and white house image by Stephen Orsillo from

Having your garage attached to your house is a wonderful convenience, especially if you live the northern climates. Parking in the garage and carrying groceries right into the house, not having to run through the rain or snow to get to your door and just the security of having your car and other possessions within walking and hearing distance are a few reasons to consider.

Things You'll Need

  • Building permit
  • Heavy equipment
  • Concrete
  • 2 by 6s
  • Insulation
  • Roofing material
  • Plywood sheathing
  • House wrap
  • Nails
  • Wiring
  • Lighting

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Always check with your planning office or other authority before building anything. Your city's building codes will need to be considered. If you live in a subdivision your neighborhood may have stipulations for your building as well.

Plan to build the garage as close to the house as possible. If the garage must be several feet away, use this extra area as a hallway or extra space for the room it is being attached to.

Remove any siding or windows from the existing house that will not be used inside the garage. One wall of the existing house will be an interior wall of the garage. The windows or doors will need to have 2 inch by 6 inch studs cut to fill the hole. Unless you leave the door as a doorway to the house. Drywall will be nailed to these studs.

Pour the concrete foundation to the height of the existing home or make plans for steps to be built to the connecting entrance. Concrete forms will be needed to square off the footers and foundation. Concrete work may be one area where you will call in a professional.

Build the wall frames from 2 inch X 6 inch boards to allow enough room for adequate insulation. Anything that touches the concrete floor will need to be treated lumber. Lay 2 X 6 boards in shorter sections to equal the the length of wall space you are building. The top plate and the bottom or sole plates will be 2 inches (actual size 1 and 1/2 inches) so an extra 3 inches in allowed for cutting each upright stud.

Cut the upright stud the height of your wall minus the 3 inches used in the top and sole plates.

Nail the upright to the top and sole plate at 16 inches "on center". Meaning the first upright will be nailed square at the beginning of the plates and the next upright will measure 15 and 1/4 inches away, allowing for the actual size. Measure 16 inches after this to mark the place where the uprights are needed for sheathing.

Lift the wall frame in place and screw it into the existing house with 4 inch screws. The screw will need to go through the two inch board and through the existing house insulation and frame, without going all the way through to the interior of the house.

Measure the space for a garage door and install the overhead fixtures. The door will be purchased with the needed hardware. Follow the manufacturers directions or consider hiring a professional.

Continue building sections of wall frame, lifting and nailing them to each other.

Nail 3/4 inch plywood sheathing to the outdoor wall frames. Staple house wrap to the entire project before you begin to add siding.

Connect the roofs at a perpendicular angle that will not create a snow or moisture problem. The slope of the garage roof will ease into the house roof. Angles will need to be continuous and not stop abruptly, creating valleys in the roof for snow or rain to collect. This is a good time to consider roofing the entire house as one roof.

Wire, insulate and drywall the interior of your garage.

Continue building the garage as your plans specify, adding siding and other finishing trim last.

Tips & Warnings

  • Consider building a separate garage and connecting it with a breezeway. The garage will be attached but the existing house will not undergo much change.


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