I am in the early stages of building a home that is completetly in flood plain in New Hampshire. The first floor will be 8′ above grade and I will have 4′ of foundation wall above grade with a slab at grade level. Slab will have drains in it to prevent hydraulic pressure under the slab and the foundation will be reinforced with a rebar grid.
The issue I have is with some openings that must be in the foundation per FEMA regulations. I have to have 1″ of opening for every 1″ of space enclosed by the foundation. I plan to do this with (2) 2’x2′ openings, one on either side of the foundation to allow for water to flow in and out freely. With eight square feet basically open, (other than some screening to prevent vermin) I have a huge heat loss area. I am looking for some type of mechanism that will allow these openings to be closed and insulated but that will open automatically in the event of flood.
There are also two 9′ garage doos and two 3′ entry doors. While these openings are large enough to satisfy FEMA requirements, they do not allow unrestricted flow. Automatic panels in these openings would be acceptable if I can find doors with that feature.
Anyone have any experience with this issue before.
Tom
Douglasville, GA
Replies
If you do a search on the internet for the louvers you will find ones with a float mechanism to open the louvers when it floods, and they return to closed position when the water receeds.
My other suggestion is if you don't have to build in a flood zone DON'T ! My new house is 125 feet higher in elevation than my old home. After living thru two floods in three years, we cut our losses and started over. Don't ever think it will never flood and it will never flood again. Don't assume the water will stop at a certain elevation.
Good luck
Tom,
Face mounted foam cored panels with float type latch.
Float on louvre handles.
Breakaway panels mounted in interior.
Float switch for the garage doors.
Only heat the garage to 40*.
Double the number of openings. On each side, in one opening set a snug cut foam panel inside the vermin screen, in the other set the panel outside the screen.
What do other locals use?
SamT
I'm also starting a house soon in a flood zone. I've been advised to get manufactured vents designed to open in case of flooding waters. Even though a screened foundation vent is permisible as a flood vent, I've been warned not to do so because of the potential of clogging with seaweed, debris, etc., which then defeats the purpose of the vent.
Thanks for all the replies. I have found a supplier of automatic vents that are priced pretty reasonably so it looks like the issue is resolved.
As far as what the other locals do, they don't do anything. Nearly all the homes built here were built 30+ years ago and don't conform. Even the modular that went in 6 years ago has a foundation that doesn't conform so I can't get a lot of local guidance.
We will be putting the first floor 5' above the 100 yr floor level or base flood elevation (BFE). There have been five flood hee since 1950 but they are a relatively mild event. I have taken all the issues into consideration prior to deciding to build here. My parents/family have had a property here for over fifty years and five floods and have never had a loss due to flood. You do have to plan for it to be four' deep in water though. I fully expect that to happen eventually. Tom
Douglasville, GA
Some are installing panels hinged to swing either way from the top. These are held in place with a toggle on each side so the local wildlife won't get in. The toggle is rather weak and is designed to fail if pressure, like floodwaters, is applied.
The panels then swing freely in the frame allowing water to come and go. Once the water leaves the hinges on top mean that, unless debris interferes, they will swing close and help keep critters out. So they said.
Saw one where the panels were painted plywood with foil-faced closed-cell foam insulation glued to the inside.