The short answer
A second story can often be added to a one-story concrete block house in South Florida, but the original footings, walls and tie beam were designed for one floor, so a structural engineer has to check them first and may call for new footings, columns or reinforcement. Zoning height limits, setbacks and HOA rules also apply, and in a flood zone an addition this size can trigger the 50 percent rule and require the whole house to meet current flood standards. Many second floors on CBS homes are framed in wood or light-gauge steel to keep weight down, and the job means removing the roof, so timing around hurricane season matters.
On a lot of South Florida streets, the only way to get more space is up. Lots are small, setbacks eat the yard, and the pool already took the rest. So the question comes up often: can a one-story block house take a second floor?
Often it can. But it is the most engineering-heavy addition a homeowner can take on, and the answer depends on things you cannot see from the street. Here is how to find out before you spend real money.
Four checks before any design
- Zoning. Your city sets maximum height, number of stories and sometimes floor area. Some neighborhoods limit second floors or require extra setbacks for them.
- Flood zone. If the house is in a FEMA flood zone and below today's required elevation, a second story is almost certainly large enough to trigger the 50 percent rule. That can mean elevating or rebuilding the ground floor, which usually changes the whole plan. See our post on the 50 percent rule.
- HOA or historic review. A second floor changes the look of the street, so expect architectural review in an HOA community or a historic district.
- Structure. A structural engineer's evaluation of the existing house. This is the one that most often decides the project, so it comes before full architectural drawings.
What the engineer looks at
A typical South Florida block house is built as one connected system: a slab and footings, block walls with steel and concrete in some of the cells, a concrete tie beam around the top, and a roof strapped to that beam. We explained that system in our post on concrete block versus wood frame. Adding a floor changes what every part of it has to carry.
| Part of the house | The question | Possible outcome |
|---|---|---|
| Footings and foundation | They were sized for one story. Can they carry two? | Sometimes yes; sometimes new or enlarged footings, or new interior footings under new columns |
| Block walls and filled cells | Is there enough reinforcing steel, in the right places, to carry the new floor and its wind loads? | Added reinforced cells or new concrete columns tied into the walls |
| Tie beam | The beam becomes the base of the new floor. Is it strong and continuous enough? | Reinforcement, or a new beam designed to receive the floor system |
| Interior walls and openings | Where will new loads come down, and where will the stair go? | New beams, posts and a stair opening in the existing ceiling |
| Wind load path | Can the whole building, old and new, resist current hurricane wind loads from the new roof down to the foundation? | New connectors and details at every joint between new and old work |
Block or wood on top?
Many second floors on CBS houses are built in wood framing or light-gauge steel rather than more block, because they weigh much less and put less load on the existing foundation. They still have to be engineered for the same hurricane wind loads, and in Miami-Dade and Broward that means High-Velocity Hurricane Zone design and approved windows and doors. A block second floor is possible too, but it usually needs more foundation work. The engineer and the budget together usually decide.
How the job runs
- Engineering, design and permits, including any HOA or historic approval.
- Foundation and wall work first, if the engineer calls for new footings, columns or reinforcement, often while the family still lives in the house.
- Roof removal. The existing roof comes off over the area being built. This is the riskiest stretch of the job, because the house is open to the weather until the new floor and roof are dried in, so we plan it outside the peak of hurricane season where possible and keep temporary protection ready.
- Floor system, walls and new roof, with inspections at each stage. In Hollywood, for example, a spot survey is required before the first tie beam inspection on an addition.
- Windows, doors and dry-in, then mechanical, electrical, plumbing and the stair connection to the floor below.
- Finishes, final inspection and an updated elevation certificate if your city requires one.
Most families move out for at least part of the job, especially while the roof is open and the stair is cut in.
When to consider something else
If the engineering says the foundation needs major rebuilding, or the flood zone rules would force the ground floor up anyway, a second story may stop making sense. Sometimes a ground-floor addition, a garage conversion or tearing down and building new on the same lot is the better value. Our demolition division's renovate or tear down guide walks through that comparison.
The bottom line
A second story on a block house is very doable when the structure, zoning and flood zone allow it, and a bad idea when they do not. Start with the engineer, not the floor plan. We build home additions, including second stories, and new homes across Broward, Miami-Dade and Palm Beach, and we can bring in the structural evaluation at the start. Tell us about your house.
Quick questions
- Can I add a second story to my concrete block house?
- Often, yes, but a structural engineer has to confirm that the existing footings, walls and tie beam can carry the new floor and current wind loads, or design reinforcement. Zoning height limits, HOA rules and flood zone rules also have to allow it.
- Will the foundation need to be redone for a second story?
- Sometimes. Original footings were sized for one story. Depending on what the engineer finds, the existing foundation may be enough, or it may need enlarged footings or new footings under new columns.
- Is the second floor built with block or wood?
- Many second floors on South Florida block houses are framed in wood or light-gauge steel because they weigh less. They must still be engineered for hurricane wind loads. A block second floor is possible but usually needs more foundation work.
- Does a second story trigger flood zone requirements?
- It can. In a FEMA flood zone, a second-story addition is often large enough to count as a substantial improvement under the 50 percent rule, which can require bringing the whole house, including the ground floor, up to current flood standards.
- Do I have to move out during a second-story addition?
- Usually for at least part of it. The existing roof comes off over the work area and a stair opening is cut into the ceiling, so most families move out while the house is open and until the new floor is dried in.
Sources
- M. Stewart, P.E., structural engineering for home additions in Florida
- Greater Fort Lauderdale Alliance, City of Hollywood permit information (survey before tie beam inspection)
- Code of Federal Regulations, 44 CFR 59.1 (definition of substantial improvement)
This article is general information, not legal advice. Building departments in Miami-Dade, Broward and Palm Beach counties set their own procedures, so confirm the requirements for your property with your local building department.
Scott Rosenberg
Florida Certified General Contractor, CGC1541479
Scott qualifies Rosemont Ventures Group LLC and has worked in general contracting since 1998. He writes Building Blocks to answer the questions South Florida owners ask before they build. Verify the license.