Since arches add unique character to a home, as an architect, I am a big fan of using them. Of course, consistency in designing with arches must be maintained to achieve a successful design solution. However, as a rule I do not mix the two different arch types in a the same design solution. These two arch types are the half round and the segmental with the difference being that the segmental arch consists of only a portion of a half round arch. Below I have listed my design criteria for using each of the arch types when designing.
HALF ROUND ARCHES
If you are stacking arches, such as the door and ceiling in this photo, keep the center point of the radii consistent. In the entryway shown here, the door unit shape determined the configuration of how the space was to be designed. By introducing a barrel vault ceiling with a radius identical to that of the door, no delineation exists between wall and ceiling. The interior decorator (Richard Black) took this opportunity to paint the walls/ceiling a dark color that causes this space to become negative and draws guests into the Great Room.
SEGMENTAL ARCHES
These arches have a softer look and I tend to use them when working with an Old World design theme. When using these arches for cased openings inside, I try to keep the widths the same. If this does not happen, you won’t be able to maintain a consistent head height and side frame height when you want the radii to be the same. Changing the widths of the openings while keeping the tops of the arches at the same height will cause some of the arches to be flatter. This will create an entirely different look and feel.
For the exterior of your home, be sure you are consistent with your arches as well. Arches are a structural shape so give them room to appear as a supporting arch–not just a tacked on element. Also note that the cost of an arched window can be up to three times as much as a square topped window.


