Let’s start with a drawing most people don’t think of as a drawing.
Before the survey, before anybody sketches a floor plan, there’s a map that has already made some big decisions about your project. It’s the FEMA flood map, and if you’re building anywhere along the Gulf Coast it sets how high you build, what your foundation is going to cost, and what you’ll pay to insure the building for the next thirty years.
The good news is that all of it is knowable on day one, before you’ve spent real money. Here’s how to read it.
What your flood zone actually tells you
FEMA publishes Flood Insurance Rate Maps that divide land up by risk. The current effective map for Lafayette Parish took effect December 21, 2018, and your local floodplain administrator uses it to set what you have to build to and what you’ll pay to insure it. You can look up any address through the Louisiana FloodMaps Portal run by the LSU AgCenter.
Three groups of zones cover most of what you’ll run into here.
Zones A and AE are the high risk inland zones, with a 1% annual chance of flooding. In AE, FEMA has already determined a specific Base Flood Elevation for you. In plain A it hasn’t, which means an engineer or surveyor usually has to establish one. Anything in a zone starting with A or V sits inside the Special Flood Hazard Area, where the strictest rules apply and flood insurance is mandatory on a federally backed mortgage.
Zones V and VE are the coastal high hazard areas, and they add wave action and velocity to the problem. Buildings here have to go up on open foundations like piles or columns, with the lowest horizontal structural member at or above the required elevation, and the space underneath has to stay clear or use breakaway walls.
Zone X is the moderate to minimal risk zone. Shaded X is the 0.2% annual chance floodplain, unshaded X is lower still. Fewer federal requirements apply, but anybody who has been through the last few flood events around Acadiana can tell you that low risk is not the same thing as no risk.
Base flood elevation, and the extra foot
The number that drives everything is the Base Flood Elevation, which is how high the water is expected to get in the base flood. The federal rule is simple enough: in A and V zones, new construction and substantial improvements have to put their lowest floor at or above the BFE. Substantial improvement means a renovation costing about half the building’s value, and that one catches a lot of owners in the middle of a project.
Local rules are where it gets more demanding. A lot of Louisiana parishes require freeboard, which is extra height above the BFE, and Lafayette Consolidated Government is one of them. In Lafayette Parish the lowest floor of a new residential structure, including the mechanical and electrical equipment serving it, has to sit at least one foot above the BFE. Non-residential buildings have to be elevated or dry floodproofed to that same one foot margin. Some parishes, Calcasieu among them, apply freeboard across an even wider set of zones.
That extra foot isn’t busywork. FEMA recommends at least a foot of freeboard, and communities that adopt higher standards earn better Community Rating System scores, which lowers flood insurance premiums for everybody in that community. Build a little higher, and the whole town pays a little less.
A real one: getting a building up out of the water without it looking like it
I was the Architect of Record on the Performing Arts Academy at Ovey Comeaux High School, back when I was at Architects Beazley Moliere. It’s a 21,000 square foot academic building with specialized music and dance classrooms and a black box theater, and the new building sat in a flood zone. Between the base flood elevation and the freeboard requirement, the finished floor had to come up roughly four to five feet above the existing buildings on that campus.
That’s a real problem, and it isn’t a structural one. A new building sitting five feet up on fill next to everything else looks wrong. It reads as something that got added on later. On a high school campus, where the new building is supposed to feel like it belongs to the same school as the old ones, that matters.
So we brought the windows down below the slab.
It sounds like a small move. It isn’t. Dropping the glazing below the finished floor line breaks up the tall blank band of wall that elevation creates, and it gives you something to look at instead of a base. From outside, the building doesn’t announce that it’s sitting up in the air. It just reads as a building with an interesting window detail, and the flood requirement is fully met either way. It’s simply no longer the first thing you notice.
There was a second requirement on that site worth knowing about. LCG required net zero fill, which means every cubic yard of dirt we brought in to raise the building had to come back out of somewhere else on the site. You can’t just truck in fill and call it done. That changes your grading, your drainage and your site budget, and it’s exactly the kind of thing you want to find at concept instead of after the civil drawings are underway.
Commercial buildings have a second option
The entry at Comeaux The steps tell you how far the finished floor had to come up to clear the flood elevationHomes and non-residential buildings get treated differently, and that difference drives a lot of commercial decisions down here.
For a house, elevation is basically the only compliant path. You raise the lowest floor above the required elevation and that’s that.
For a commercial or other non-residential building in an A or AE zone, NFIP rules give you an alternative. Instead of elevating, you can dry floodproof, which means making the structure watertight below the flood elevation with walls and openings built to resist water pressure. For a retail strip, a medical office, or a warehouse where a raised floor would wreck your accessibility and your loading, floodproofing is often the better move. Two catches: it has to be certified by a registered design professional, and it does not satisfy V zone requirements at all.
Which one is right depends on your use, your parking, your insurance math, and how the building has to meet the street. That’s a decision worth making early, and it’s one we work through with owners on commercial projects all the time.
Elevation certificates
Once a building in or near the floodplain is up, an Elevation Certificate documents where the lowest floor actually landed relative to the BFE. Lafayette’s floodplain administrator keeps these on file for new and substantially improved buildings in the floodplain, and your insurer will want one to rate the policy correctly. A clean certificate showing a foot or two of freeboard can bring your premium down, which is one more reason to design above the minimum instead of right at it.
Find the number first
Here’s where I see people get hurt. They treat the flood zone as a permitting step instead of a design decision, and by the time the number finally shows up, the project is already drawn.
Say your lot is in AE with a base flood elevation of 12′-0″, and Lafayette wants a foot of freeboard on top of that. Your finished floor has to sit at 13′-0″. That one number sets your foundation type, how long your accessibility ramp has to be, where the driveway ties in, where the condensers sit, and how the building meets the ground when somebody walks up to it. Find that out at concept and it’s just a constraint you design around, like any other. Find it out after the drawings are done and you’re reverse engineering the whole project around a number you should have started with.
And if you’re already past concept and only now learning your elevation, you’re not stuck. There are usually two ways forward. You can raise the structure and rework the approach and site drainage around it, or on a commercial building you can look at dry floodproofing instead, which keeps the floor down but has to be certified and won’t work in a V zone. Which one is cheaper depends on your use, your parking, and how the building has to meet the street.
If you’re looking at a property right now
If you don’t know what zone it’s in, that’s a ten minute answer. Send me the address, or just call or text me at 337.454.5457, and I’ll pull the map and tell you what you’re actually dealing with.
It’s a whole lot cheaper to know now than to find out in month four.
Adam Beazley, AIA, LEED AP is the founder and principal architect of A Beazley Architecture, an award-winning firm based in Broussard, Louisiana. With over 22 years of professional experience in commercial, institutional, and religious architecture, Adam specializes in contemporary, resilient design across the Gulf Coast. Licensed in Louisiana, Texas, Alabama, Mississippi, and Florida with an NCARB certificate. Adam leads a kingdom-minded firm committed to designing buildings that serve clients missions, strengthen communities, and stand the test of time.