How do I know if my house is below or above the Advisory Base Flood Elevation?
The easiest and most accurate way, is to hire a licensed surveyor to do an elevation certificate for your home. This will cost about $400. If you choose to raise your home, it will have to be done again, after the home is raised to obtain your certificate of occupancy. He will use equipment to determine what the elevation of your first floor is. This is not the height off the ground, but the height above sea level. This will tell you how far above or below the ABFE your first floor is. You do not necessarily have to obtain an elevation certificate prior to raising, working with numbers provided by a surveyor, your contractor can make an accurate determination when he is preparing to raise your home.
You may also make a rough estimation, by following these steps.
Step 1: There are several Apps available that will pinpoint your location, through Global Positioning Satellites (GPS), or the US Geological Survey, and tell you what level (height above sea level), the ground is around your house. We cannot personally confirm the 100% accuracy of these apps, so please use your discretion. For instance, test it out on a known elevation first, for accuracy. The App will give you a number, which you will need in Step 2.
Step 2: Once you have determined approximately how high your ground is above sea level (Step 1), take a measurement from the ground to the top of the first floor of your house (the flooring).
Step 3: Add those two numbers together (Step 1 and Step 2). If the elevation of the ground around your house is 5’ and your first floor is 3’ off the ground, then your first floor elevation is approximately 8’. If your house is on a slab, your first floor elevation is going to be the same as the ground.
Step 4: Now, go to www.region2coastal.com/sandy/table, and enter your address in the address field, and select “Get Details.” Make sure the house that is flagged on the map is your home. Scroll down under the map and look for “Advisory Base Flood Elevation,” ABFE. Take that number, and subtract the elevation of your first floor (the total from Step 3). If the ABFE is 9 and your first floor estimate is 8, you are approximately 1′ below ABFE. We would recommend going at least 1’-2’ above ABFE. In this example you would want to raise your house 2-3 feet, bringing it to a height of 10-11 feet, above sea level, not off the ground. While you are at the site to determine your ABFE, be sure to make a note of what “Zone,” you are in. We will need that information later, to determine what type of foundation is recommended for your particular zone. It will likely be AE, A or V.
Clear as mud from Superstorm Sandy, right? Remember, this method is no where near as accurate as hiring a licensed surveyor. This just may give you a rough idea of how high your home (first floor) is, compared to the new flood advisories, and help give you an understanding of what all these numbers mean. If you took on water during the storm, that can also be a good indicator that you are below the base flood elevation. However, even if you did not take on water, your home still may need to be raised. Your township will only make you comply with these heights if your flood repairs exceed 50% of the value of the structure, if you demolish and build new, or if you decide to do an addition or remodel, in the future, that exceeds 50% of the value of the structure. However, even if you are not required to comply with the new flood advisories at this time, your insurance rates will rise substantially if your home is below the Advisory Base Flood Elevation.