Enclosing a Lanai in a Fort Myers Flood Zone
Updated: 3 days ago
A contractor in Fort Myers asked us to help a homeowner turn the covered lanai of a one-story block house, built in 2004 per the plans, into a real room. The plans show the lanai at about 110 square feet. The kitchen wall and the garage wall formed two sides, and the other two sides were open, one to the pool deck and one to the side yard. The plan: close in the two open sides, put a sliding glass door in each, bring the floor up to match the house, and cool the room with a ductless mini-split.
No new footprint and no roof work. On paper it is a small permit job. It still touched the flood rules, the wind rules, the energy code and the zoning setbacks, and one of those turned into a real decision for the owner.
What the elevation certificate showed
The house is in flood zone AE (a mapped flood area with a set flood height) in unincorporated Lee County. The base flood elevation (the mapped flood height) there is 11.0 feet, and the design flood elevation on the plans is 12.0 feet, one foot above it. Before the set could go in, we needed an elevation certificate. The plans reference it, and the floodplain reviewer compares the drawings to it.
The certificate, prepared by a licensed surveyor, put the house floor at 10.70 feet, the garage slab at 9.10 feet, and the ground beside the house between 8.61 and 8.78 feet. Two things followed from those numbers.
First, the new room's floor stays below the base flood elevation, the same as the rest of the house. The plans show the lanai slab about 5 inches lower than the house floor, and the set brings the new floor level with the house. Because the floor stays below the design flood elevation, the set calls for flood-damage-resistant materials below that line. It also notes that Lee County reviews the work for substantial improvement, the County's check of whether a project is big enough to trigger flood upgrades for the whole house.
Second, the north door would open about two feet above the side yard.
The door that ended up two feet off the ground
With the floor at 10.70 feet and the yard at about 8.6 feet, the first step out of the north slider is roughly 23 to 25 inches down. So the drawings show new concrete steps down to the yard.
Here is the catch. The site plan, drawn from the survey, shows the house 6.3 feet from the north property line, inside a 6.5-foot side setback. The Lee County code allows steps in that setback only at the main entrance, and this slider is not the main entrance, so the County has to agree to the steps.
The owner chose to keep the sliding door with the steps and ask the County to accept them. The drawings show the steps, and the County will decide at permit review.
The walls, the doors and the wind
The two new walls are concrete block, filled in under the existing tie beam (the concrete beam along the top of the block walls that carries the roof). The plans show that beam already spanning both openings, so no new beam was needed.
The design wind speed is 160 mph, and the site is in the wind-borne debris region. Both sliding doors are impact units rated to resist wind-blown debris, with a Florida product approval, installed per that approval, and the glass is labeled safety glazing.
The garage wall now borders living space
This part is easy to overlook. Once the lanai is air-conditioned, the wall between it and the garage separates living space from the garage. On this job that wall is insulated like the new walls, and the fire separation between the house and the garage stays intact with no new openings. The old wall to the kitchen becomes an interior wall, and the kitchen door stays.
Energy compliance is shown on a signed Form R402, the short Florida energy code compliance form, that went with the set.
The mini-split goes up, too
On this job the outdoor unit sits on a stand or wall bracket with its base at or above the 12.0-foot design flood elevation.
What this means for you
This lanai enclosure looked small. In a flood zone, the heights on the elevation certificate drove the floor, the materials, the steps and where the air conditioner goes.
What to do
Get your elevation certificate early. If your house is in a flood zone, ask your surveyor for one before the drawings start. On this job the floor and grade numbers decided a lot.
Look at the grade outside each new door. On this job one door opened about two feet above the yard and needed steps.
Check your setbacks. Here the steps fell inside the side setback, where the code allows steps only at the main entrance.
Ask about the garage wall. On this job the wall shared with the garage had to be insulated, with the fire separation kept intact. Ask whether yours does too.
Ask where the outdoor unit goes. Here the outdoor unit sits on a stand or bracket at or above the design flood elevation.
Use impact-rated doors with a Florida product approval. Both sliders on this job are.
For more on our work in the area, see our Fort Myers structural engineer page and our home additions page.
FAQ
Did this lanai enclosure need a full permit set?
Yes. On this job it took a signed and sealed permit set and a signed energy form, ready to submit to Lee County, where the floodplain reviewer compares it to the elevation certificate because the house is in zone AE.
Did the floor have to be raised to the flood elevation?
On this job, no. The new room's floor matches the existing house, below the base flood elevation, with flood-damage-resistant materials below the design flood line. Lee County's substantial-improvement review decides what applies to a given house.
What are the new walls made of?
Here the walls are concrete block infill under the existing tie beam.
Why is the air conditioner on a stand?
On this job the outdoor unit sits on a stand with its base at or above the design flood elevation, as the drawings require.
Questions about enclosing a lanai or porch? Call Michael D. Stewart, P.E. at (239) 292-7670 or contact us.
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