by the Center for NYC Neighborhoods
You will also need to install flood vents in the remaining aboveground portion of the basement or crawlspace. While filling in your basement may be costly up front, it can end up saving you thousands of dollars on your flood insurance premiums in the long run. In some cases, filling in your basement could damage the structural integrity of your building, so it is essential that you consult an engineer before taking action.
If your home is in a special flood hazard area, the primary factor in determining your flood insurance rate is the difference between the elevation of the first floor of your home (this is the basement floor) and the Base Flood Elevation. By filling in your basement and installing flood vents, you decrease that difference, because your next floor above ground becomes your home’s lowest floor for insurance purposes. This will lower your flood insurance premium, but the size of the premium decrease will vary, based on the elevation of the ground compared to the BFE.
By eliminating your basement and installing flood vents, you will raise your home’s lowest floor elevation without actually lifting the house — your first floor above ground will become your home’s “lowest floor elevation.” When you fill in your basement, you also ensure that all of your contents are located above ground level, making them less likely to be damaged in the event of a flood. Installing flood vents protects your home’s foundation and walls from being damaged by water pressure. However, in order to fill your basement you may have to give up part of the livable area of your home, so you should consider whether these benefits outweigh the loss of this space.
Filling the basement or crawl space and installing flood vents can be expected to take one to two weeks on average, after all permits are obtained and construction begins.