How flood water gets into a house is almost never through the walls. It comes in at five openings, and most homeowners have only ever thought about two of them.
Concrete block and stucco hold water reasonably well for the length of a storm. Walls are not the problem. The problem is every place a builder cut a hole in one.
Water is patient and it is lazy. It does not force its way through anything. It finds the lowest gap it can reach and goes there. So if you want to know where your house is exposed, you do not need an engineer. You need to walk the perimeter and look at five things.
1. The front and back doors
An exterior door sits on a threshold, and that threshold has a gap under it. It has to. The door needs clearance to swing, and the sweep on the bottom is built to stop drafts and insects, not standing water.
Weatherstripping is designed for rain hitting the door sideways and running off. It is not designed for four inches of water sitting against it for six hours. Under sustained pressure, that seal gives up.
What to check: put your hand flat on the floor inside the door on a dry day. If you feel outside air moving, water goes there too.
2. The garage door
This is the big one, and it is the one people underestimate most.
Your garage door is the widest opening in the building, sitting at the lowest point of the structure, sealed by a strip of rubber resting on a concrete slab. Sixteen feet of gap, an inch off grade, held back by a bulb seal. It was never meant to be watertight.
Driveways also slope toward the garage by design, so rainwater runs away from the street and toward your door. That works fine in an afternoon shower. In a flood it means the garage collects everything the driveway gathers.
Then there is what is in there. Water heater, electrical panel, washer and dryer, HVAC air handler, the second car, and every box of things nobody could bring themselves to throw away. A garage flood is rarely just a garage flood.
3. Sliding glass doors
Sliders are worse than they look, for a reason that surprises people.
A slider sits in a track, and that track has small drainage holes in it called weep holes. They exist so rain blown into the track can drain back out to the patio instead of pooling in the channel. That is good engineering for normal weather.
But drainage runs both directions. When water outside rises above the level of those weep holes, they stop draining out and start letting water in. The feature that protects the door in a rainstorm becomes an open pipe in a flood.
Most Florida homes have sliders on the lanai or pool deck, which is often the lowest, flattest part of the property.
4. Vents and wall penetrations
Walk the outside of your house and count the holes. Dryer vent. Bathroom exhaust. The line set where the refrigerant lines enter from the condenser. Hose bibs. Electrical and cable service entries. Crawlspace or foundation vents if you have them.
Every one of those is a hole cut through the envelope of your house and sealed with caulk or a plastic flange. Caulk is a ten-year material at best in the Florida sun, and most of these penetrations sit within two feet of grade.
What to check: anything below knee height with cracked, missing or chalky caulk around it. That is a five dollar fix on a dry Saturday and an expensive problem in February.
5. The one nobody checks: your drains
Here is the opening that catches people completely off guard, because it is the only one where the water is already inside.
Your home connects to the municipal sanitary sewer. During heavy sustained rainfall, groundwater and stormwater infiltrate that system faster than it can carry the volume. When the main surcharges, it has to go somewhere, and the path of least resistance is the lateral running to your house.
Water comes up. Toilets, shower drains, floor drains, the laundry standpipe. It arrives from the lowest fixtures first, which usually means a ground floor bathroom or a garage floor drain.
Two things make this worse than the other four. It is not rainwater, so the cleanup is a different category of job entirely. And you can seal every door and window on the property and still get it, because it did not come in from outside.
This is what a backflow prevention system is for, and it is a separate conversation from barriers.
Walk it once, on a dry day
Take fifteen minutes this week. Start at the street and walk the perimeter of your house.
- Note every exterior door and how high the threshold sits above the ground outside it
- Look at where your driveway slopes and where it ends
- Check the slider tracks and how low they sit relative to the patio
- Count your low wall penetrations and look at the caulk
- Find your lowest interior drain, and know where it is before you need to
You will end up with a short list, and it will be shorter than you expect. Most Florida homes have three or four real vulnerabilities, not twenty. Knowing which three is most of the work.
Do it on a clear day, with a tape measure, when nothing is coming. Measuring your own openings in the rain is how people end up with the wrong answer twice.
If you want the timing argument for why this matters this particular winter, we covered that separately in our post on what a historic El Niño means for Florida flood risk.
Dam It Defense builds custom flood barriers measured to the specific openings on your home, fabricated and installed in Florida. If you would rather not guess which of the five is your problem, we will come look and tell you. The assessment is free.