Designing and Building in a Floodplain

Waterfront properties are among the most desirable home-sites in the world. Living on the water offers incredible views and recreational activities. However, they may also be in the floodplain. The Federal Emergency Management Agency (FEMA), ranks Travis County (including Austin, Texas) in the Top 10 % of counties in the nation that are at risk for significant flood damage. Along with the beauty and allure of owning waterfront property comes the challenge of building within an established flood zone or flood plain area.

The two primary documents for designing & building in the flood plain (zone) are ASCE 24-05 (American Society of Civil Engineers) and FEMA 54 (Federal Emergency Management Agency). ASCE 24-05 & FEMA 54 engineering standards are broken into two basic categories: Step 1: Function and Step 2: Form / Aesthetic. (“It’s not just what it looks like and feels like. Design is how it works.” -Steve Jobs). The final step (Permitting) confirms that the first two steps were followed properly.

STEP 1 – FUNCTION

• All structural components must be adequately connected to prevent flotation, collapse, or permanent lateral movement. FILL DIRT MUST REMAIN STABLE UNDER FLOOD CONDITIONS!
• All service equipment must be elevated above the flood zone – including heat pumps, air conditioners, hot water heaters (tankless), circuit breakers, electrical junction boxes, outdoor appliances, etc.
• Any space designed for habitation MUST be elevated above the Flood Zone.
• Permitted in the Flood Zone: vehicular parking, limited storage and building access (stairs). Elevators are permissible subject to separate design guidelines.

REDUCING HYDROSTATIC PRESSURE

Constructing a crawlspace beneath the first floor will raise the lowest floor of the structure above the surrounding grade. Openings in the foundation walls are then required. If flooding reaches the building, the openings allow flood waters to enter the area below the lowest floor and equalize the hydrostatic pressure on the foundation walls.

WIND

Buildings elevated above the ground can be more vulnerable to wind. Add to that the desire to capitalize on the beautiful view with large windows, and there is often the need to consult a professional who understands both structural engineering as well as the specifications and tensile strengths of both window frames and glass.

STEP 2 – AESTHETIC

Design to meet performance standards, but don’t forget:

• VIEW (We paid for lake views, we want lake views)

• SUN ORIENTATION

• WIND

• NEIGHBORHOOD / DESIGN GUIDELINES

Technique #1: Raise the lowest floor

Technique #2: Design lower level of house as non-habitable and build habitable home above floodplain

STEP 3 – PERMIT

Getting a permit in a floodzone adds a level of complexity that necessitates experience and patience. In fact, any  property within a certain perimeter of a body of water, even if not in the floodplain, adds an additional layer of complexity. There is no standard process for obtaining a permit. Every property is different. The following agencies and permitting authorities may be involved in obtaining a permit in a floodplain project.

• Local HOA
• County office
• City office
• LCRA (Lower Colorado River Authority)
• Water District

For more details on what is/is not allowed within a floodplain project, see City of Austin Land Development Code 25-7-92, 93, 94, 95 & 96…

Jenkins Design+Build has designed and built more floodplain homes in the Austin and surrounding areas than just about any builder in Central Texas. If you have questions, we would be happy to help.

Contemporary Home Design in the Floodplain

This fun contemporary home design was created for a client requesting floodplain house plans for a lot on Lake Travis.  This client does a lot of entertaining and has very close friends who spend time with her at her home after they have spent the day on the water.  The wine room is a place for them to sit and enjoy conversations and fine wine while watching the sun set on the lake and Hill Country.  The concept for the wine room is an open round room with wire racks holding the wine.  The backing is planned to be a small glass tile lit with cove lighting from above to give the room some pizzazz!

Notice, also, how the house is laid out.  Originally, these clients were going to sell the lot, after a large home went in next to them, blocking their view (or so they thought).  We really had a vision for that lot and house design, and they allowed us to show them what we were envisioning.  Once they saw how we were able to keep their view of the lake, give the house that contemporary flair they wanted, and keep the house out of the floodplain, they were on board.  We are really excited about this amazing project!  We are so fortunate to be us and get to do what we do!