Engineering

The Appeal I am seeing more and more requests for hangar home combinations where the living area is built above the hangar. Around the Internet there are a few pictures of projects, some which have not yet been built, which show nice and neat depictions of this type of an arrangement. Its appeal, on certain levels, is easy to understand. Such an arrangement can be tidy and well contained and not be as sprawling as other types of projects with hangars on the same level as living area, or even separate. There can be some advantages to having the living area over the hangar. This type of an arrangement can lend to very nice opportunities to view the runway from the comfort of one’s home. With the living room, or family room or other common areas of living space set over the hangar these can be designed to face the runway giving the occupants a wonderful theater from which to watch their fellow pilots land airplanes. This can be quite enjoyable as any pilot knows who has sat in a chair applauding, and perhaps judging, landings of his compatriots. This arrangement can be advantageous for narrow lots where separate hangar and living structures might force the living area to be built away from the runway with the hangar between. While this may be something desired in some cases, I find that many folks, if on the runway, request some sort of runway view. If the lot is small this can be difficult to achieve by any other means. Going “up” with a design has some inherent efficiencies in that the same roof covers both living area and hangar and the same slab, or lower floor, functions for both areas. There is an ongoing debate in the industry as to which is cheaper to build, a one or a two story home. In my own evaluation I have found two to be comparable when all elements are taken into consideration. But nonetheless there is an inherent efficiency to having the home rest over the hangar area. The Challenges and Solutions However there are several disadvantages and challenges for this type of arrangement and this could be the reason why there are not more of these types of structures to be found. The key problem with having the hangar under the living area is that, given the typical sizes of hangars, usually at least 2000 ft.² with a typical width of 50 feet, it is difficult to span that distance with any structural element that can withstand the deflection  forces of the live loads. Though structural elements can be designed to hold the weight the problem falls in the area of deflection which can manifest in what is called, in the industry, “bounce”. Bounce is basically the vibration which can be detected by human occupants as a result of shifts in position of various users of the space.  One can be sitting in the living room and have a group of children running across the living room and actually feel the vibration of their movement in the floor and furniture. This can be unsettling. Though not an actual structural problem it is more a problem of perception. It is, by its nature, somewhat subjective but studies have been made on the subject and bounce is a real potential problem. The only solution to the bouncing problem is to have the structural member designed with enough stiffness to resist deflection. Stiffness is largely achieved by a structural element's depth. If one is using a beam of even 2 feet of depth across the 50 foot span this would generally not be sufficient to handle the “bounce” to the extent most people would find desirable. Of course, these factors can be controlled by limiting the size of the hangar but generally most folks want to have at least 2000 ft.² of hangar space and a typical size for this is 50’ x 40’. The 50 foot side is usually the side for the hangar door. Running the beam from front to back would have its own inherent problems of causing a substantial point load in the middle of the hangar door header system. So limiting the size of the hangar can certainly mitigate some of the bouncing problem. It is a matter of whether or not the owner is willing to live with a smaller hangar. I have had owners quite satisfied with smaller hangars. Another solution is to add a post to the beam. This makes all the differences by, effectively, cutting the beam length in half (if placed in the center). One of my clients, in North Carolina,, is parking a relatively small home-built airplane in his hangar and is able to tolerate a post set in the middle of the long beam. He is able to easily park his aircraft in the space despite the post. Another strategy is to use a “T” hangar where the tail, or even the nose, rests in a more narrow portion of the hangar. This design segregates the rear left and right corners of the hangar into either living areas or some type of shop or storage space. It opens up the opportunity to create load-bearing members in strategic locations to reduce the length of the main supporting element for the home upstairs. Another, less common, strategy is to create a “wall truss”. This can be a major wall contained within the living area upstairs which is designed as a deep truss to support secondary floor and roof structures. Passageways through the truss can be challenging and that is part of the job of the designing engineer to solve. Three Other Challenges. The living area over hangar concept can be “boxy”. There are ways around this but the basic massing of this type of structure is a challenge that needs to be handled in most cases. Secondly, this type of arrangement puts most of the living area on the second level requiring either stairs or an elevator for egress. If the owners are entering the senior status of life this can be a factor and an elevator is can be the best solution. And, finally, if the hangar exceeds 2000 sqft in size, substantial fire separation requirements can kick in. These require special structures in the ceiling of the hangar to separate the hangar and living spaces. This is quite technical, and can usually be solved. A Trend that begs for Solutions It appears there may be a trend pointing to an increased popularity of the home over hangar arrangement. I think it behooves designers and engineers to begin solving this set of interesting challenges. Homes over hangars can be quite charming and even include decking placed in front of the home, over the hangar, providing a great area for relaxing and watching the aviation experience.