Floodproofing

Install Dry Floodproofing: Sealants & Impermeable Membranes

What Is It?

Dry floodproofing techniques can be used to make a structure watertight below flood elevation. Impermeable membranes and sealants can be used to seal walls to reduce or prevent the penetration of floodwater through walls. Membranes and sealants are typically applied to exterior wall faces, making them cost-effective options for retrofitting existing buildings. Tests using sealed and sheet membranes used over concrete walls have yielded ¼ to 4 inches of leakage after over 24 hours of exposure to 3 feet of flooding. Particularly in structures with basements, walls and floors must be specifically designed to resist hydrostatic pressure. If design loads in dry floodproofed buildings are exceeded, buoyancy forces can actually cause more damage to a building than would have occurred if the building were simply allowed to flood. The success of interior floodproofing in protecting a building from flood damage will depend on the depth, duration, and velocity of the flood. For buildings in the most vulnerable flood zones, dry floodproofing will be most effective when multiple measures are combined. Wall sealing should be combined with other measures like flood shields for maximum protection. Internal drainage systems (e.g. sump pumps) may also be employed, as sealed walls can still leak in longer, deeper flood events. Sealants and membranes should be inspected regularly for cracks and potential leaks.

Benefits

Cheaper than other retrofitting methods for floodproofing
Applied to the building itself and does not require additional land (for floodwalls or levees)
Easily combined with other dry floodproofing measures (e.g. flood shields/barriers, sump pumps) for maximum protection
Does not require human intervention during a flood event for protection

Drawbacks

Membranes and sealants do not protect structures from high-velocity flood flows and wave action
Dry floodproofing measures cannot be used to bring substantially damaged or substantially improved residential structures into compliance with floodplain management ordinances and laws
Regular inspection and maintenance required to ensure continued functionality

Regulatory Impacts and Requirements

Potential regulatory touchpoints in Boston and Massachusetts include:

Building Code/Permit

Financing Options, Incentives, and Rebates

FEMA Hazard Mitigation Assistance: FEMA provides funding for flood and disaster mitigation through three grant programs: Hazard Mitigation Grant Program, Pre-Disaster Mitigation, and Flood Mitigation Assistance. Additional information and application instructions are available here through the Massachusetts Emergency Management Agency. Only non-residential dry floodproofing projects are eligible.
Hazard Mitigation Funding Under Section 406 of the Stafford Act: Local, state, tribal, and some non-profit facilities damaged by disasters may use Section 406 funding to restore damaged facilities, as well as undertake preventative measures for future flood mitigation.