+ Reply to Thread
Results 1 to 6 of 6
  1. #1
    Join Date
    Jan 2008
    Location
    Southern Maryland
    Posts
    2

    Post Cost to Add Bonus Room to Garage

    I am looking for any ideas on how difficult and how much it would cost to have a bonus room added on top of my existing garage. I have a small 2 story colonial with a large 1.5 car side load attached garage. The garage footprint is roughly 20'x20'. The current garage is all exposed framing and has no finished attic space or insulation. The only side that has drywall is the side that attaches to the house. The house is built on a crawlspace and the existing block foundation wall was extended around the garage and a concrete floor was poured. As a result, I do not believe there would be any issues with the foundation being able to support the load of a second story.

    The main question I have is how much would I expect it to cost to rip the existing roof off and add a second story? Our basic concept for the second story would consist of a large dormer window facing the street side of the house with a sloped roof line that squares off after the peak as it goes to the back of the house. The back side of the addition would probably be cantilevered ~2' over the garage to match the rest of the house and maximize the added space.

    Electric would need to be fed in from the garage below, the ceiling of the garage would need to be insulated and vented, a doorway added to the bonus room from the top of our existing 2nd floor stairs, and ductwork would need to be extended to provide a couple of additional vents to the room (assuming existing heat pump is adequately sized for the additional space). If anyone has a rough idea on what I could expect to pay to add a bonus room of this scale, please respond to this thread. Any help, input, or recommendations would be appreciated.

  2. #2
    Join Date
    Aug 2007
    Posts
    612

    Default Re: Cost to Add Bonus Room to Garage

    You would have to get the scope of what you want defined and get a few estimates. I would think with the housing slow down you wouldn't have a problem getting someone to price it out for you. Be up front with potential contractors about the budget you have in mind and how serious you are with following through. They will not appreciate putting a lot of time into an estimate for a tire kicker.
    My SWAG on something like this for our area would be $100/sq ft and that will vary depending on a lot of variables, like # of windows, siding, roof line, etc., etc.. Your area may be different. In addition to many other items, you need to verify your present heating/cooling could handle the extra load and making sure to isolate the upstairs from the garage area according to fire codes.

  3. #3
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Cost to Add Bonus Room to Garage

    Eric ... that will be a nice addition .

    One of the first considerations will be the condition of the blocks and the footings in place for the garage also if they are substantial enough for the additional load for the proposed room.

    Depending when the house /garage was built and your municipality there may be copies of the original building plans available for you to obtain. This can be useful in determining what was specified for the garage portion of the foundation as well exploratory excavation would also reveal this.

    Second thing will be to evaluate the existing structure of the garage to ensure there are no problems with things like rotted bottom plates or insufficient anchoring, etc..

    There will be the need to reinforce the existing garage structure to accommodate the floor structure above. Having a span of 20 feet will likely require a support beam ( likely steel) midspan to carry the floor joists. The engineered joists can have the advantage of spanning this distance though they will would be sized accordingly by an engineer and likely be closely spaced (for example 12 inch spacing) which does add to the cost.

    The existing garage door opening will have to be beefed up as well. If the existing door opening is 16 feet the header will not be enough to support the added load which will require to increase the support or change to two 9 foot doors.

    As a suggestion consider the use of closed cell 2 lb. spray foam insulation applied to the underside of the floor....... if applied properly will provide an excellent insulation and air seal ensuring the exhaust gases from the garage won't infiltrate the room above. The ceiling of the garage would then be covered with 5/8 drywall.

    The third consideration will be if your existing HVAC system will accommodate the extra 400 square feet of conditioning.

    As for the price ... that would be determined by labor costs in your area , material costs at the time , finishes , and special considerations required by the local building codes .... a guesstimate would be in the area of $100/sq foot.

    Good luck and hopefully this helps.

  4. #4
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Cost to Add Bonus Room to Garage

    Geez .... it seems my slow typing did it again.
    My apologies for duplicating much that bp21901 already stated.

    Keep in mind that there will be no way of providing more accurate dollar values to the addition without complete building plans.... and those won't include the unforeseen and the "you-might-as-well" things.

  5. #5
    Join Date
    Aug 2007
    Posts
    612

    Default Re: Cost to Add Bonus Room to Garage

    Quote Originally Posted by canuk View Post
    Geez .... it seems my slow typing did it again.
    My apologies for duplicating much that bp21901 already stated.

    But you were much more complete and eloquent than I!! Funny that we picked the same $/sqft swag. I would have thought you would price in m^2!?

  6. #6
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Cost to Add Bonus Room to Garage

    Quote Originally Posted by bp21901 View Post
    But you were much more complete and eloquent than I!!
    Yep ... that's me Mr Eloquent .... naw ....that's the reason for the slow typing.


    Funny that we picked the same $/sqft swag. I would have thought you would price in m^2!?
    It's hell having to always do conversions ....

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •