Adding a room onto an existing home is probably the most cost effective way to increase a building’s usable interior space. In this article, an addition means what a colleague calls a "three sided" addition. This phrase intends to avoid confusion with other sorts of home additions such as raising a building to create a new ground level space, or raising the roof to create a story between a ground level space and a roof area. The three sided addition means that the new and existing building will share an interior wall.
The first consideration when planning an addition is headroom: the height of a ceiling relative to human proportions. Most building codes stipulate minimum ceiling heights, but, as most people prefer ceilings that are at least eight feet (2.5 m) high, a well-designed space will probably meet or exceed these. Ensuring adequate headroom is probably the most challenging aspect of addition design, and is the main reason to start planning an addition from the roof down.
Begin your design thinking by trying to envision what you consider an ideal ceiling height for your addition when finished. As mentioned, most prefer a minimum eight feet, but a few inches less than this will still work in a pinch. It is important to start here, because your new ceiling will likely be hanging from the roof framing that will, in turn, attach to the existing building. If this framing attaches to an existing building too low, your ceiling will be too low. Let’s look at a couple standard roof frame techniques to help clarify.
Gable Dormer: When most kids in the western world draw a house, it will have a gable roof. A gable roof is an upside-down "V." A gable dormer is this same roof shape attached to an existing main building at a right angle. It will have a peak as does the children’s drawing, and where its roof meets the main roof is called a valley. As people have been using gable dormers for centuries, you won’t need to look far for an example. The main advantage to a gable dormer when designing an addition is that the addition’s ceiling height is determined by how high its peak is relative to the main building. Typically, the higher the peak, the greater the available ceiling height.
As with any building project, there is seemingly no end to pro and cons, and compromises need be found. When using a gable dormer frame for an addition, the compromise is that much of its weight will bear on the existing or main roof framing because it overlaps this framing. As the main roof framing was not likely designed to support this extra weight, this main roof frame will need to be strengthened. Of course, there are a few more in and outs to know about putting a lid on your addition using the gable dormer method, but in my opinion, this method is the slickest, and in the long term, will offer better looks than most alternatives. Due to the structural bolstering, and other framing elements required when using a gable dormer, it will likely cost more, as well.
Page 1 of 3 :: First | Last :: Prev | 1 2 3 | Next