One of the most asked for and least understood option for a pole building is designing for an attic “bonus room”. A bonus room is exactly what it sounds like – it is extra space, a “bonus”.
For sake of simplicity, let’s think about this in the realm of only a gable style roof. A gable roof has a slope on each side and the peak directly in the center. While we can engineer some very sophisticated areas, the idea here is to create some affordable space.
In order to maximize the usable space, it is best to go with the steepest possible roof slope. The limitation will be most prefabricated roof truss companies can only build and deliver trusses which have a 12’ overall height. This means the roof slope limitations are about 11/12 for 24’ wide buildings, 9/12 for 30’ wide, 7/12 for 36’ wide and 6.5/12 for 40’ wide. Clearspan widths of greater than 40’ are just not practical or affordable.
Now the fun parts! How wide and tall will this room be? The room width will be approximately ½ of the span of the truss. As the truss span increases, the room width will become slightly less than ½. How tall will it be? Plan on a 7’6” tall finished ceiling. Allowing for ¾” oriented strand board (osb) on the floor and 5/8” drywall, the framed height is usually 7’8”.
If you are drawing this out on paper, you will see a portion of this room is going to have a sloped ceiling. The areas towards the eave sides of this room become far too short to walk, or even crawl in.
How will this room be accessed? As you are now creating a building with a mixed occupancy – with garage/shop/storage below and living space above, the two areas must be separated by a one hour fire assembly. This will typically entail two layers of 5/8” Type X drywall on the ceiling of the lower level. Stairs require the same degree of fire protection, so often it is most practical to create a deck off one end of the building, with a door into the bonus room from the deck, and stairs to the deck.
If the floor level of the bonus room is over 12’ above grade, a landing will need to be provided in the run of stairs. The landing dimensions must be at least equal to the width of the stairs.
Prudent design would also place a window large enough for egress in the end of the bonus room opposite the stairs. A four foot square sliding or single hung window will be adequate for these purposes, and will afford ventilation.
With proper planning a bonus room can be a valuable addition to your property. As a general rule of thumb, the resale value of this created space is double the cost of the improvement!