River bottom · Sienna, Texas
Foundation Repair in Sienna, TX
The most very high clay of any town on our launch list, a levee district of its own, and permits that depend on which side of a line you're on.
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- Town-by-town soil data
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- Call (832) 539-7922
Sienna's homes are young, but its ground is some of the most active around Sugar Land. Eighteen of the 25 spots we sampled sit on soil in the USDA's top shrink-swell class. Among the 12 towns we wrote about first, no other had more. Most Sienna homes were built after 2000, and they sit behind a levee system run by Sienna's own levee improvement district.
That adds up to a few questions worth answering before any foundation repair in Sienna: which clay is under the house, what the levee does and doesn't do, and whose permit rules apply. Here's what the public records say.
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The Ground Under Sienna
On the state geologic map, 17 of our 25 Sienna spots fell on river deposits, and most of the rest, along the eastern edge of our grid, on the coastal prairie's Beaumont Formation. In the soil survey, the 25 spots split this way:
- 18 very high. Lake Charles clay covers 8, mostly in the east, reading 13.6 from about a foot down. Brazoria clay covers 6 and reads 17. Churnabog clay, from a map unit the survey calls "frequently flooded, occasionally ponded," covers 3 and reads 14.3. One spot landed on Pledger clay at 19.
- 2 high. Belk clay (7.5) and Edna (6.6), one each.
- 5 moderate or low. Norwood covers 4, reading 5.0 or 5.9 in one thin layer, and a Clemville soil covers 1, at 4.6.
So most Sienna slabs rest on clay that swells hard when it's wet and shrinks hard when it's dry, on the river side and the prairie side alike. Brazoria clay is 64% to 73.5% clay and reads 17 all the way down, with no calmer layer underneath within the survey's 80 inches.
On ground like that, ask how deep any repair piers will go. The Foundation Performance Association, a Houston-area group of engineers and repair firms, warns that piles not driven deep enough below the soil's active zone can keep settling. The USDA's free Web Soil Survey will show which of these soils is under your lot, and our soil guide explains each one.
Flood Zones in Sienna
We checked FEMA's flood map at all 25 spots. Of those, 9 fell inside the 1% annual chance floodplain, 4 of them in a mapped floodway. Another 8 sit in an area FEMA labels as having reduced flood risk due to a levee. The other 8 landed in the area of minimal flood hazard.
The levee belongs to the Sienna Parks and Levee Improvement District, which Fort Bend County created in 1978. The district says it covers about 9,832 acres, including Sienna, Sienna Point and Southern Colony, and that its system also protects Waterbrooke West and Oyster Creek Farms. It's split into two levee systems by a county channel. The north system has two pump stations with a combined pumping capacity of 286,400 gpm (gallons per minute).
The district is candid about the limits: "Remember, we are behind a levee!" it tells residents, urging them to look at flood insurance. It also says its flood gates begin to close when the Brazos reaches 39.9 feet at the Richmond gauge, below the river's 45-foot flood stage. After that, rain inside the levee has to be pumped out. Our flood zones guide explains how to read your own flood map.
Sienna Homes by Decade
The Census counts 7,168 homes in Sienna, and the median one was built in 2007:
- Before 1960: 0.8%
- 1960s: 3.8%
- 1970s: 0.9%
- 1980s: 1.6%
- 1990s: 12.3%
- 2000s: 45.3%
- 2010s: 28.5%
- 2020 or later: 6.8%
That's 92.9% of homes from 1990 or later. A young house on very high clay can still move, and a new crack doesn't mean anyone cut corners. Post-tensioned slabs, with steel cables stretched tight inside the concrete, are common in homes of this age, and a stamped notice in the garage floor often says so. Anyone planning to drill, saw or core that slab should map the cables first.
If your Sienna house is still within a builder's warranty period, read it before booking any work. A foundation inspection gives you floor readings to share with the builder.
- 2007Median year Sienna homes were built
- 0.8%Built before 1960
- 92.9%Built in 1990 or later
Source: US Census Bureau, American Community Survey 5-year estimates, 2023.
Permits and Rules in Sienna
Sienna is split, and the line matters:
- The Sienna MUD No. 2 area was annexed into Missouri City in 2023, so Missouri City's permits apply there. The city asks contractors to register before any work, at $105 a year.
- The Sienna MUD No. 3 area is still outside city limits, so Fort Bend County's rules apply. The county has adopted no building code for single-family homes, but it requires a Development Permit for building modifications and work in the 100-year floodplain.
Missouri City has proposed annexing the MUD No. 3 area, with council action tentatively set for December 7, 2026.
If that goes ahead, Missouri City's rules would apply there too. Which streets fall in which district isn't something we can tell you from the records; Missouri City's annexation page has the maps. Ask the right office, the city or Fort Bend County Engineering at 281-633-7500, before work starts. Our permits guide covers both.
Foundation Repair Services in Sienna
- Slab foundation repair For slabs on Brazoria and Lake Charles clay
- Pier and beam repair For raised floors over a crawl space
- House leveling When a newer home's floors slope
- Foundation inspection To get readings before any quote
- Foundation crack repair To tell a finish crack from a structural one
Sienna Questions
Is Sienna part of Missouri City?
Partly. The Sienna MUD No. 2 area joined Missouri City in 2023. The MUD No. 3 area is outside city limits for now, with annexation proposed for December 7, 2026.
What do Sienna's drought rules allow for foundations?
That's up to the Sienna utility districts, and their drought plans aren't posted online. Ask the district on your water bill what its stages allow. Don't assume Missouri City's schedule applies to you.
Does living behind a levee make a Sienna house safe from flooding?
It lowers the risk but doesn't remove it, as FEMA and the levee district both say. Heavy rain while the flood gates are closed has to be pumped out.
Nearby Towns on the Same Ground
We serve Sienna and the towns around it, including Fresno, Missouri City, Stafford, Sugar Land and Pearland.
Fresno, the nearest, is all prairie clay: 24 of its 25 spots came up high or very high. Sugar Land shares Sienna's Brazoria clay and its reliance on levee districts. See all service areas.
Get a Free Foundation Inspection in Sienna
Let us know what's changed in your Sienna home. A foundation repair company that serves Sienna will take floor readings and explain them without pressure. You pay nothing for the visit.
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