Many people dream of owning a beach house or a vacation forest cabin on stilts. Many have done just that. So if your mind’s set on this, you’ll need to think: How high can you build a house on stilts?
Local and regional codes for stilt houses’ heights follow a level maximum of 35ft and higher on slopes. Federal disaster regulations set a 1-2 feet minimum base flood elevation (BFE). Prefabricated stilt houses vary between 10 – 20 feet high and over 25 feet in coastal, hurricane, and flood zones.
Building codes control stilt houses’ heights, and what’s feasible is determined by a site’s ground conditions. The Flood Emergency Management Agency (FEMA) sets stilt houses’ minimum height in flood and disaster areas (BFE limits). Area-specific controls regulate the maximum of 35 feet or two stories on level ground. However, there’s more.
Building Codes Regulate Stilt Houses’ Heights
Height is crucial if you’re building a house on stilts, and as building regulations and codes aren’t uniform across regions, you need to know how high you can build. These codes are area-specific and mainly differ from one area to another. Building codes also take the terrain into account to decide what’s permissible. The latter also affects what’s feasible.
Generally speaking, local governments (cities, townships, and counties) have their specific regulations for the heights of houses on stilts. These zoning ordinances control the absolute heights of stilt houses amongst others.
Typically, the purpose of the stilts is to raise the house above the base flood elevation. Sometimes, local governments authorize a limited exemption from maximum heights to accommodate building elevation for flood protection purposes (see below FEMA regulations).
However, contact your local government’s planning, community development, and building department for all stilt houses for information on what’s permissible. The following section deals with specific building codes.
Building Codes Define The Height of Houses on Stilts
Zoning and building codes follow the 1960s height rule that allows a maximum 35 feet height or two stories restriction for a residential building on a level lot. This height for a building on level terrain appears straightforward but is not as easy to apply when you build a house on stilts on a slope.
A stilt house might be in the 35 feet mark, but in actuality, the stilt house’s height might be 38 feet or 55-60 feet high or even higher. This difference is because the dwelling space itself adheres to the maximum 35 feet height, but the overall height (elevation) is higher on stilts.
As district building codes differ too, you can find instances with up to 100 feet maximum height on 10 acres, and in Oregon, there’s a 40 feet high house on stilts. With no absolute height for stilt houses on slopes, the American Planning Association (APA) recommends that a stilt house’s height on the downslope be raised and lowered on the upslope.
How the height of houses on stilts is taken as the vertical distance from the ground to the highest point and as a slope is not at the average graded ground level, this is more intricate. Also, a two-story restriction is inadequate as in many instances, such regulation doesn’t cover a half-story, an attic, basement, or cellar.
Permissible Versus Feasible Height For A Stilt House
In general, there’s no maximum permissible height for a house on stilts as it’s a raised structure that’s often not on level ground. The height of a stilt house is influenced by the slope and the geophysics of the site, which a structural engineer will need to survey to determine the maximum feasible (rather than permissible) height.
Though the actual height of dwellings is regulated at a level of 35 feet (as seen above), regional and local authorities can decide differently. This height is often controversial as different states rule according to their area-specific codes, which can be complicated.
However, prefabricated stilt houses adhere to a minimum of 1-2 feet off the ground and stand from 10 to 20 feet high, even over 25 feet in coastal, hurricane, and flood plains. In New Jersey, the 35 feet or two stories level height measurements are adhered to, and here an engineer’s certification is needed for heights greater than 42 feet.
What’s permissible, as seen above, has to be feasible too for the site you’ve chosen to build on. The terrain of the site is important (see below).
Terrain Determining Height For A House On Stilts
Bylaws and building codes require that a structural engineer’s drawing comply with the demands of the terrain and that an elevation certificate be signed off before the building process starts, during the process, and once a building is completed.
Though California’s picturesque houses on stilts in Los Angeles’s San Fernando Valley (built in the sixties) appear to defy building codes, California’s current building standards strictly require building permits for any structure. Also, elevation certificates based on FEMA’s Flood Zone Map are needed.
These elevation certificates detail the relationship between the terrain or site where the stilt house is proposed and the actual structure of a house on stilts. Knowing how high you can build a house on stilts depends on the terrain’s specific ground-bearing conditions, which engineers locate through geophysical mapping techniques (see below).
Structural Engineer’s View On The Height Of Stilt Houses
A structural engineer decides on what’s feasible regarding the height of a stilt house. This possible height has to do with the geophysics of the landscape or the character of the terrain, and the engineer will do a geophysical survey to see the site’s specific ground conditions.
These explorations entail radar and seismic impact studies that look for radar and seismic effects present. This kind of exploration plan of the terrain is presented in a report that looks at, amongst others:
- Ground contamination – unstable soil
- Type of contamination
- The possible flow of contaminants (distribution) and the spread (migration) of pollutants
- Survey of groundwater flows (hydrology)
These geotechnical, geo-environmental factors determine the maximum feasible height for stilt houses. These maximum heights are used with standard minimum heights (see below) set by the Federal Emergency Management Agency (FEMA) to approve a place on stilts.
Minimum Height Requirements For Houses On Stilts
A maximum height for stilt houses depends on many variables. But required minimums are set by the Federal Emergency Management Agency, especially in coastal, flood, and disaster-prone zones.
Often, flood plain administrators will also advise on minimum heights, which can be seen in the strict standards set in New Jersey on minimum requirements. This base flood elevation of a house on stilts (BFE) can vary, though, but not below the set minimum.
In New York State, there’s a restricted height of at least two feet higher rather than the standard 1% annual chance flood elevation regulated. In the Florida Keys, stilt houses are built at least 10 feet or more above the floodplain, and a minimum of seven (7) feet above mean sea level in flood zones.
South Carolina’s stilt houses near the ocean, along tidal rivers, near marshes, and in low-lying areas are rarely more than 20ft above sea level. Applications here require that a survey is done on the soil types there, determining the height of stilt houses.
Besides the maximum permissible and feasible heights and the minimum prescribed heights, stilt houses’ heights are restricted by a neighborhood’s character and the costs of building on stilts (see below).
Neighborhood’s Character and Costs Influence Stilt Houses’ Heights
A stilt house is required to fit into the neighborhood’s character, which means that a house on stilts relates to already built dwellings’ heights. A house on stilts also is not allowed to intrude on a neighboring house’s right to privacy, their view, or block light from that house.
The most contentious here is to design a house on stilts that preserve the essential vistas and stick to height regulations. From a planning perspective, it’s possible, according to the American Planning Association, to plan for a view.
The costs of stilt houses are steep, and on average, these are approximately one dollar per foot per square foot of footprint. What it costs to build a 1000 square foot building, at the point when you’re pouring the foundation, is an additional $1000 for each added foot of elevation.
Living in a house high on stilts has elements of romance, and is mostly a necessity but often an expression of the magnificence of architects’ designs for elevated dwellings. Whether built to defy winds and waves, or pure fantasy, stilt houses’ heights are governed by a non-standard set of building codes and regulations.
So if you decide to dwell above terra firma, there’s more to consider than views and sunsets. The rules and regulations for minimum and maximum heights, costs, and the geophysics of the terrain are deciding factors in how high you can build on stilts.