Houston new builds: the 500-year floodplain rule that sets your slab height

Charos Peña · 2026-11-08T06:43:17-08:00

Builders and wholesalers pricing Houston teardowns: check the 500-year floodplain before you check comps.Since September 1, 2018, the City of Houston's Chapter 19 rules require new homes in the 500-year floodplain, not just the 100-year, to be built 2 feet above the 500-year flood elevation. From the Freese and Nichols summary of the April 2018 council vote:1) It covers new construction and substantial improvements, which includes expanding a building's footprint by 33% or more.2) Zero net fill now applies in the 500-year floodplain too. Fill you bring in to raise the pad has to be offset on the same site, so you can't just truck in dirt.3) Harris County's separate 100-year rules don't apply inside the city limits, so a lot inside Houston and a lot in unincorporated Harris County are underwritten differently.What it means for a wholesale price: a lot in shaded X can carry a different build cost than an almost identical lot two streets over outside it. If your ARV comps are homes built before 2018, the cost to hit that elevation isn't in them.And FEMA's own number: 25 to 30 percent of NFIP flood claims are paid on properties outside high-risk areas.Builders: drop the areas and lot size you're buying below. Wholesalers: drop the zip, price and ARV below and I'll tell you if the numbers hold.

Ametria Chaney

Realtor · Memphis, Shelby County · Member since 2026 · 395 posts · 135 votes

5d

Great breakdown, Charos — this is exactly the kind of detail that can quietly change a deal's math. The elevation requirement isn't just a building code footnote; it shows up in fill and foundation costs, in the timeline, and in what a buyer will pay for flood insurance later, so it has to be priced in before the offer, not discovered during the build. I see the same lesson here in Memphis, where flood zones and drainage can vary street to street — the FEMA map is a starting point, not the whole answer. An elevation certificate and a real insurance quote early on can save a lot of second-guessing. For anyone pricing a teardown, I'd also compare only to post-2018 builds when possible, since older comps don't carry that same cost.

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Charos Peña

OP

Real Estate Agent · Houston, TX · Member since 2026 · 47 posts · 7 votes

4d

Ametria, agreed on post-2018 comps. Two things I'd add for Houston:

1) The comp set I trust on a teardown is homes finished after Chapter 19 took effect on September 1, 2018, in the same floodplain band. A 2016 build next door wasn't held to 2 feet above the 500-year elevation, so it isn't the same product even if the square footage matches.

2) The finished value hits the carry, too. Texas appraises property at market value as of January 1 (Tax Code 23.01). A builder who carries a finished spec home into January pays that year on the finished value. In the City of Houston the city rate alone is $0.51919 per $100, about $4,670 a year on a $900k home, before county, school district and any MUD.

In Memphis, does the flood elevation cost get priced into the lot, or does it land on the end buyer?

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Max Comperatore

Technology · New York, NY · Member since 2026 · 71 posts · 19 votes

1d

Charos, the two-foot freeboard is a cost line, not a code footnote, and Ametria is right that it belongs in the offer, not the build.

A two-to-three foot pad raise over an 1,800 sf footprint under zero net fill runs $18k-$32k installed: import offset, compaction testing, engineered slab, elevation cert. Horizontal infrastructure adds $18k-$28k per pad. That capital sits in cost basis, never in ARV. At 70% LTC on $30k of pad you draw $21k at an 8.39% debt constant (7.5%, 30-year amortizing), $1,762 of annual debt service. A 1.25x DSCR floor credits 80 cents on the rent dollar, so you need $184 per month of incremental rent to carry it. Shaded X comps will not pay that premium.

Then the carry S-curve. Spec exposure is not linear. Months one through four are quiet, five through nine is where the curve steepens, so a home delivered in October that has not cleared by January 1 gets taxed on finished value. Charos, your $0.51919 city rate on $900k is $4,673 before county, school, and MUD.

The question is not whether the lot sits in shaded X. It is whether your basis survives when the lender marks LTARV and the pad dollars earn no multiple. Charos, Ametria: what is your all-in per-pad basis with freeboard, and at what LTARV does it stop clearing 1.25x?

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Charos Peña

OP

Real Estate Agent · Houston, TX · Member since 2026 · 47 posts · 7 votes

1d

Max, fair push.

1) I don't have a sourced per-pad cost for freeboard fill in Houston, and I won't make one up. Builders here have real bids, and that's the number I'd want in this thread.

2) On a for-sale spec, DSCR isn't the test. The construction lender sizes on LTC and LTARV, and the end buyer's flood quote decides whether the ARV holds. That's why I comp only post-2018 builds in the same floodplain band.

3) You're right on timing. Texas values property as of January 1 (Tax Code 23.01), so a spec finished in October and still unsold at New Year carries a finished-value bill for the next year, and the city rate is only one line of it. In a MUD the total can be far higher.

Builders: what did your last pad raise in the 500-year floodplain actually cost per home? Drop the areas and lot size you're buying below.

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Houston new builds: the 500-year floodplain rule that sets your slab height

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