Elevating a Home

We have learned over the years that elevating a home in the floodplain can be challenging. There is no playbook that can be created that gives you a step by step guide. Each Situation is different and each structure might take a different path to get elevated. Ultimately, doing your elevation correctly will result in reduced flood damage and cheaper flood insurance premiums.

The Rock Island County Floodplain Ordinance has specific requirements for elevation buildings in §154.616.B. The building can be constructed on fill, elevated on solid (flow thru) walls or constructed with a (flow thru) crawlspace. Floodplain areas within Rock Island County can be fairly deep. In these cases, the structures are typically elevated on solid walls or piers. Therefore, the information below will focus on this type of structure and construction.

Step 1 - Look at the Flood Insurance Rate Map (FIRM)

The very first thing to check for in any discussion about a project in the floodplain is whether or not the project location is in the State regulated floodway, or the flood fringe. If you are here, you already know you’re are in the mapped floodplain. The main floodplain (AE Zone) along the Rock & Mississippi Rivers has two layers:

Floodway - Any development activity within the floodway needs a permit from Illinois Department of Natural Resources – Office of Water Resources (IDNR-OWR). This is the area on the FIRM that is blue and red cross hatched. Once you obtain approval from the State, then you are required to get a permit from our office.
Flood Fringe – This is the area within the floodplain (AE-Zone) that is not State regulated and you can just deal directly with our office. This is the area on the FIRMs that is blue (not cross hatched).
Other Flood Zones – There are other flood zones in Rock island County. If you are building in any of these other flood zones, please contact our office to discuss.

Step 2 - Find Your Elevation

Get a surveyor or engineer. You will need to get elevation information to decide how far above ground you structure will need to be to protect it from flood damage. As part of the building permit process, you will need to provide an Elevation Certificate (EC). The EC will show the ground elevations, lowest floor, lowest point of your mechanical equipment, the top of the main floor, and the Base Flood Elevation (BFE). Throughout your project, we will need two EC’s. One at the beginning, based on construction drawings and then a final one, showing the structure's as-built elevation. Once the project is completed you can get an occupancy permit.

The most important thing you will need from the surveyor or engineer is a benchmark. A benchmark is a point the surveyor or engineer will set that will be used as a reference mark. Typically, we see a nail or spike set in a tree to telephone pole. Something that will not move during construction. The surveyor or engineer will provide you with documentation that will show what elevation the benchmark is set at and what the Flood Protection Elevation (FPE) is. The FPE is the elevation which your top floor and all mechanicals must be above.

We highly recommend that after you get your foundation installed, that you have the surveyor or engineer come back and transfer that bench mark to new foundation so that all of the contractors working on project know not to install anything below that elevation. This also makes it easier for your inspector to verify your mechanicals are at the correct elevation.

Step 3 - Building Components

Draft a good set of plans. Work with a design professional that will ensure that the building will be compliant when finished. Make sure plans contain all of the materials you plan to use so we can review them prior to starting construction.

Flood Resistant Materials - When you build, all materials located below the FPE, must be flood resistant. Flood Resistant means "Any building material capable of withstanding direct and prolonged contact with floodwaters without sustaining significant damage". For example, wooden door frames and window jambs will swell and will likely not operate properly after exposure to flood waters. Lastly, don’t store items in the lower enclosure that can’t get wet and that you don’t want ruined.

Foundation - The floodplain requirements focus on the portion of structure which are exposed to flood waters. In other words, those parts of the structure below the Flood Protection Elevation (FPE). Above the FPE, there are no special requirements, just following the adopted building codes. Here are some specific components of the foundations that can get confusing when building in the floodplain:

Lower Enclosure. We will refer to the area inside the foundation as the lower enclosure or an elevated crawlspace. Whether you are building a new dwelling or elevating an existing structure, these are the same. The foundation will be either concrete, block or piers. This enclosure can only be used for parking of vehicles, storage, and building access. No areas shall be partitioned within the lower enclosure, only structural walls are allowed. It must have flow thru vents that allow water in and out of the lower enclosure without human intervention. This area cannot be used for human habitation.
Floor. The floor inside of this lower enclosure must be at the existing grade, or slightly above. No part of the enclosure can be below grade. You are required to install flood vents, at least one, on all 4 sides, and they must be within one foot of bother interior and exterior grade.
Flood Vents. If walls are used, all enclosed areas below the flood protection elevation shall address hydrostatic pressures by allowing the automatic entry and exit of flood waters. You must have a minimum of one (1) permanent opening on each wall no more than one (1) foot above interior or exterior grade with a minimum of two (2) openings. The openings shall provide a total net area of not less than one (1) square inch for every one (1) square foot of enclosed area subject to flooding below the base flood elevation. The total amount of floods vents needed is directly related to the size of the lower enclosure. There are many different models of engineered flood vents, each model is unique and come with a certification, hang on to that paperwork.
Piers. Other types of foundations, such as piers that may hold up your home or maybe just your deck shall be anchored, designed, and certified as to minimize exposure to hydrodynamic forces such as current, waves ice, and floating debris. The design methods to comply with ese requirements must be certified by an Illinois lessened professional engineer or architect.

Mechanicals – All of the mechanical and electrical components and systems are required to be at or above the Flood Protection Elevation (FPE). Some of the most common ones are your gas & electrical meters, water well system including the well head and pressure tanks, electrical outlets, light switches, light fixtures, HVAC ductwork, air conditioning condenser, water spigots, etc. These are just some but are some of the more challenging items to plan for. Utility companies have specific requirements for meters when they are elevated high off the ground.

Energy Code - The Illinois Energy Conservation Code can add challenges to designing these homes. Defining your thermal envelope along with flood resistant materials is challenging. Our regulations do not allow this area to be climate controlled. So typically you will be insulating the floor and not the exterior walls of the lower enclosure.

Step 4 - Get a Permit

This is the step where you will submit the set of plans, your State Permit (if in the floodway), an elevation certificate, your recorded non-conversion agreement and your typical documentation for any construction project. Our staff will review your plans and required documentation, then we will issue a building permit. Having an experienced general contractor can save a lot of headaches on complicated projects in the floodplain.

Step 5 - Start Building

You now have a bench mark, a good contractor, and a good set of plans. Make sure every contactor on site understands the FPE mark the surveyor has set and to keep everything above that elevation. If assumptions that were made when drafting your plans change, stop and re-evaluate. Talk with your contractor and architect. Have the general contractor reach out to one of our certified floodplain Managers (CFM). Make sure to get appropriate inspections along the way.

Step 6 - Certificate of Occupancy

Before you schedule that final inspection, you will need to provide a copy of the final Elevation Certificate (EC) showing as-built elevations and a copy of your signed non-conversion agreement. Once you have your documentation, you can schedule your final inspection with the Building Inspector(s) and Floodplain Manager.

Conclusion - Floods Will Happen

Remember that the intent of these rules is to protect your investment from being damaged by flooding. Building correctly will help reduce the disruption that you and your family will experience during a flood event. You are basically designing a structure to live in the water part of the year. Clean up after a flood will take time and the less components of your structure that are affected, the easier it is to recover. All of these are added stresses in your life that we all want to minimize.

The biggest takeaways from this page for your project are:

Paperwork - State Permit, Good plans, Elevation Certificate & Non-Conversion Agreement.
Elevation - Your first floor and ALL mechanicals are above the FPE.
Lower Enclosure - Flood vents, interior grade vs exterior grade, flood resistant materials & no interior walls or rooms.