Bonus Room Over The Garage Challenge!
Sounds simple enough doesn't it? Deceptively simple, I reply.
Building a bonus room over a 3 car garage is easy. Doing it correctly is another thing!
We've all heard that it's cheap SF, in fact it's almost free! Well, it's less expensive than kitchen SF but certainly not free. There is also the cheap bowling alley method and the more sophisticated, expensive method.
What make that building space so challenging?
1. There is attic space on 3 sides and a garage on the other.
2. Providing enough daylight.
3. The space is long and narrow.
4. Attic ventilation is more difficult to achieve.
5. HVAC design.
6. Strange design ideas.
Let's take each issue, one at a time.
1. Summer attic temperatures in Central Florida can exceed 150 degrees F. Unlike most parts of a home, bonus rooms have attic space on three sides. Additionally, due to truss configuration they are difficult to insulate with fiberglass batts. Special care must be taken when insulating.
Though I'm not normally a fan of spray foam insulation, a bonus space over a garage is ideal for spray foam. Foam provides a high R value in a small space and normally you only have 4" in which to insulate. The thickness of the vertical truss 2x4 web.
The floor of the garage bonus, normally a has plenty of space to insulate with an R- 30 fiberglass batt but care must be taken to place insulation up against the bottom of the sub floor and not suspended below the floor sheathing leaving an unconditioned air space between the batt and the sub floor.
2. Sure it's easy to position a single or double window at the far end of the room but that makes the room feel like a bowling alley. Other lighting options must be explored. The dreaded skylight that always leaks, dormer windows or some other light providing design. Doing it right is obviously more expensive.
The very last thing you want to do is install double french doors with an exterior balcony at the end of a bonus space. That's a guaranteed leaker!
3. The typical 3 car garage dimensions are 32' wide x 22' deep. When building a bonus room, the goal is to get maximum useable SF. Certainly not a ceiling height of 2' but something reasonable. I've stretched to a 4' height at the extremes.
The trick here is the interface between Architect, Homeowner, Builder and the truss manufacturer. There is a point of diminishing returns where the cost of engineering a longer truss or closing the spacing between them exceeds the benefit. This is where hiring the right building team comes in.
4. Attic ventilation is of particular concern with a bonus space above a garage. Most attic spaces are ventilated by air flowing into perimeter soffits, rising along the attic side of roof sheathing then exiting vents positioned toward the peak of the roof. Anything that blocks that air flow is a problem. An over heated attic space can cause a lot of issues from cooling of the interior bonus space to moisture removal.
As soon as a Builder expects a tradesman to see an issue that is beyond his normal thinking, there is a problem. Expecting a painter to think "waterproofing", a framer to think "attic air flow" or a roofer to think "attic Ventilation" there is going to be a problem. THE BUILDER IS THE ONLY TEAM MEMBER THAT SEE THE ENTIRE PICTURE. That's why hiring the right Builder that has years of experience is so vital. He knows from years of problem solving what to look out for. He know because it bit him in the butt before!
5. The best way to air condition bonus space is with it's own designated unit! It's difficult enough to condition living space that has attic space on 3 sides and a hot garage on the other, without tacking the bonus space air conditioning on to a system that is already cooling another part of the house. If you don't want to have a hot bonus space, better make sure it has it's own HVAC unit.
This is an area where the Builder has to bring the HVAC contractor into the the design early to avoid issues down the road. It's too late once the house is designed and the framing is complete. At that point, all the HVAC contractor can do is make the best of a bad set of options.
6. Strange design ideas is another area of concern. I've seen dormer windows that are 2' wide drawn on plans by Architects. Why is that an issue you ask? A narrow dormer translates into a long unusable light-shaft in a bonus space. Depending upon the pitch of the roof, a poorly designed dormer can be a huge waste of space and an eyesore. Imagine a 3' wide space 10' long! I'm not talking about just one of these, picture 2-6 of these baby's! Now you get the picture! Big time ugly!
A dormer can be designed in such a way to make it wider so it can be a space with a desk or other useable area not some ugly unusable light shaft.
As you can see, a well designed bonus room is not just some after thought that is slapped on a home design at the last minute. It takes a team of dedicated members lead by an experienced Builder to do this correctly.
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