Understanding Design Limitations
On the Revised Flood Maps, Special Flood Hazard Areas are now broken into Coastal High-Hazard Areas, which include not only Velocity Zones (Zone VE), but also Coastal AE Zones (Zone AE with Limits of Moderate Wave Action - LiMWA). Design requirements now mandate the design standards for foundations within these newly created “Coastal AE Zones” to match those for foundations in Velocity Zones. Design of these foundations must accommodate unobstructed flow of flood waters to a greater elevation than would be required within the AE still water flood zone. These houses are often elevated on timber piles, concrete piers, or other materials that allow waves to passed beneath the structure without damaging its supports.
Design requirements have also increased for houses within the lower “Hazard Flood Zones” (Zone AE with wave heights less than 18 inches and Zone AO, or so called “Overwash Zones”). The revised Massachusetts Building Code now requires residential buildings within these zones to design to a greater elevation than the previous edition. The newly designated “Design Flood Elevation” (DFE) is the “Base Flood Elevation” (BFE) plus 1 foot of freeboard, which places the lowest floor and utilities for new construction a foot higher than would have been required in 2017. As was the case with the 8th Edition of the Building Code, any enclosed space below the Design Flood Elevation must be made flood resistant and may only be used for storage, parking, or access. In no instance can the enclosed space below the lowest living space be constructed below ground on all four sides (no basements).
Mitigating Flood Insurance Costs
For homeowners looking to reduce flood insurance premiums and construction costs resulting from the FIRM and Building Code updates, the first step would be to retain an engineer with a good working knowledge of not only the FEMA flood zone regulations, but also State and Local ordinances. The engineer should be able to guide the property owner through design limitations and the permitting process. The first step to be taken is preparation of an Elevation Certificate. The Elevation Certificate will provide the insurance company with risk assessment information that they otherwise may not have had which, could potentially reduce an insurance premium. The Elevation Certificate will also provide the engineer with pertinent information necessary to develop mitigation strategies to reduce potential flooding risk and to further reduce insurance costs.
In order to prepare an Elevation Certificate, a survey of the property is performed to obtain the building floor elevations, ground elevations around the building, location of the utilities, flood vents, and other site improvements. This information along with information obtained from the FIRM is recorded on the Elevation Certificate. If it’s determined by this survey that the house has been improperly shown within a Flood Hazard Area, a determination can be sought from FEMA through the Letter of Map Amendment (LOMA) process.
After the Elevation Certificate has been completed and the insurance company has updated the premium, the engineer, insurance agent and a local builder can run through a cost-benefit analysis to determine:
a) Potential improvements that could be made to mitigate flood insurance costs;
b) How the improvements would reduce your risk exposure;
c) What the costs would be to make these improvements.