Check Your Impervious Cover Before You Build in Austin
Your Austin lot already has a house, a garage and a paved area out front. Now you want a big deck and a covered patio out back, and nobody has told you there is a cap on how much of the lot can be covered.
Most Austin house lots zoned SF-2 or SF-3 can have no more than 45 percent impervious cover. Rooftops count in full, so a solid patio cover adds to the total. An uncovered wood deck with gaps over open ground counts at half its area.
- SF-2 and SF-3 lots top out at 45 percent.
- A roofed patio cover counts like a roof.
- An uncovered gapped wood deck over open ground counts at half.
- A pergola with an open top is a different case to ask about.
What the Limit Is
The Land Development Code table sets the maximum impervious cover by zoning. It is 45 percent for SF-2 and SF-3, 40 percent for SF-1 and 25 percent for RR.
What Counts Toward It
The calculation rules include buildings and other hard surfaces that keep rain out of the ground. The city glossary lists rooftops, walkways and some decks.
| Build | Counts toward the cap |
|---|---|
| Solid patio cover or roof | Full area |
| Uncovered gapped wood deck over open ground | Half the area |
| Loose landscape gravel, no compacted base | Not counted |
How Decks Are Treated
An uncovered wood deck with drainage gaps between the boards, built over open ground, counts at 50 percent of its area. Put a solid roof over that same deck and the roof counts as a rooftop. That makes the choice between a pergola and a solid cover matter on a lot near the limit.
It Also Shows Up on Your Bill
The city drainage charge is billed on impervious cover, measured from aerial photos taken every two years. The city says the bill may be lower for an uncovered wood deck.
The Gaps
Deck ideas rarely mention the cap at all. On lots over the Edwards Aquifer zones there is a second layer of rules from the state, covered on the TCEQ private residences page.
Answers in a Sentence
What is the impervious cover limit for SF-3 in Austin?
45 percent of the lot.
Does a wood deck count as impervious cover in Austin?
An uncovered deck with gaps over open ground counts at half its area.
Does a patio cover count?
A solid roof counts like any other rooftop.
Where We Got This
- Land Development Code 25-2-492 Site Development Regulations (table), City of Austin, via Municode Library
- Land Development Code 25-8-63 Impervious Cover Calculations, City of Austin, via Municode Library
- Glossary Terms, City of Austin Development Services Department
- Drainage Charge, City of Austin Watershed Protection Department
- Edwards Aquifer, Private Residences, Texas Commission on Environmental Quality
Elsewhere on the Site
Where to Find Deck and Patio of Austin
706 W Ben White Blvd A, Austin, TX 78704
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