DIY vs installed flood barriers
Do-it-yourself barriers such as sandbags and door dams can divert a few inches of standing water but are not watertight. Installed panels and shields seal openings more reliably, but FEMA limits sealing a house to flood depths of about 2 to 3 feet, not where there are waves, and both kinds must be in place before the water arrives.
There are two broad ways to keep shallow floodwater out of a house's doors and garage: things you put down yourself when a storm is coming, and barriers designed and fitted for your openings. Both have the same limits on depth and waves. They differ in how well they seal, how fast they go up and who has to be there.
The limits that apply to both
- Shallow water only. FEMA says sealing a house is practical only where flood depths are no more than 2 to 3 feet; masonry walls tested to about 3 feet, and frame walls are likely to fail at lower depths (FEMA, chapter 7).
- No waves. FEMA says sealing is not appropriate where there is wave action or high-velocity flow (FEMA, chapter 7). On ocean and bay fronts the protection is elevation.
- Up before the water. Neither kind works if it is still in the garage when the tide comes in.
- Not a code fix. FEMA says sealing may not be used to bring a substantially damaged or substantially improved house into compliance (FEMA, chapter 7). See renovating in a Hamptons flood zone.
Side by side
| Do-it-yourself | Installed | |
|---|---|---|
| Examples | Sandbags, store-bought door dams and inflatable or water-filled barriers | Aluminum flood panels or planks on fitted tracks, flood shields, flood doors |
| Seal | Not watertight; sandbags are for diverting water (USACE) | Designed to seal a specific opening; ask for the tested water height |
| Effort | Filling and placing; each sandbag weighs 30 to 50 lb (USACE) | Panels drop into tracks; time depends on how many openings |
| Testing | Usually none | Some products are certified to ANSI/FM 2510; check the listing, not the brochure |
| Storage | Bags, sand, pumps | Panels and hardware, labeled by opening |
| Best for | Short-notice, shallow water; backup | Houses with repeat shallow flooding and someone available to deploy |
What ANSI/FM 2510 does and does not tell you
ANSI/FM 2510 is the American National Standard for flood mitigation equipment. It covers opening barriers such as flood doors, panels and planks, and tests hydrostatic load, leakage and impact. It also states that "flood barriers for coastal applications are not included in the scope" (FM Approvals, ANSI/FM 2510). A certification tells you how a product performed in a test, at a stated water height. It does not tell you your house will stay dry in a coastal storm.
Questions to ask before buying either
- What is the flood zone and base flood elevation at the house, and how deep has water been at the doors?
- Is the house masonry or frame, and is the floor slab sound?
- What water height is the product tested to, under which standard, and can you see the certificate?
- How long does it take to put up, and how many people does it need? Get the time in writing.
- Who will put it up if you are not there? See protecting a second home.
- Does the town or village need a permit for the mounting hardware or a flood door?
- What about water coming up through drains? FEMA treats backflow valves as part of a full sealing plan (FEMA, chapter 3).
For local rules, see flood protection for Hamptons homes. For insurance, barriers on a home earn no NFIP discount: see flood barriers and flood insurance.
Frequently asked questions
- Are sandbags enough to protect a house?
- For shallow, standing water they can help divert it, but the Army Corps of Engineers says sandbags are not watertight. They work best as a backup, and they take time and people to fill and place.
- What is ANSI/FM 2510?
- It is the American National Standard for flood mitigation equipment, published by FM Approvals. It covers opening barriers such as flood doors, panels and planks and tests hydrostatic load, leakage and impact. It states that flood barriers for coastal applications are not included in its scope.
- Can flood barriers protect an oceanfront house?
- Generally not. FEMA says sealing a building is not appropriate where there is wave action or high-velocity flow. Oceanfront and bayfront homes in V and Coastal A zones rely on elevation.
- Do I need a permit for installed flood panels?
- It depends on the town or village and on the work. Permanent mounting hardware, flood doors and anything that changes the structure may need one. Ask the building department before buying.