Concrete patio in Austin: three things to settle first
A patio is simple concrete with three Austin-specific questions attached: does it fit under the lot's impervious cover limit, is it inside a protected tree's root zone, and does it drain away from a slab foundation that sits on clay. Answer those, and the pour is the easy part.
Concrete patio cost in Austin
| Patio | Area | projectcosted Austin ($5.63 to $11.26) | HomeBlue Austin ($6 to $10) |
|---|---|---|---|
| 10x10 | 100 sq ft | $563 to $1,126 (published) | $900 to $1,500 (published) |
| 12x12 | 144 sq ft | $811 to $1,621 | $864 to $1,440 |
| 12x16 | 192 sq ft | $1,081 to $2,162 | $1,152 to $1,920 |
| 16x20 | 320 sq ft | $1,802 to $3,603 | $1,920 to $3,200 |
| 20x20 | 400 sq ft | $2,252 to $4,503 (published) | $3,400 to $5,900 (published) |
| 20x30 | 600 sq ft | $3,377 to $6,755 (published) | $5,100 to $8,800 (published) |
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Unmarked rows are computed from each source's per-square-foot rate. Steps, a thickened section for a hot tub, tear-out of an old patio ($1.10 to $1.70 per sq ft, HomeBlue Austin) and pump access are extra.
Impervious cover: the patio question unique to Austin
The City of Austin defines impervious cover as the area of surfaces that keep water from soaking in, including paved areas and walkways, and its residential permit worksheet has a line for “Uncovered Patio.” Single-family SF-3 lots are generally capped at 45 percent, and some watersheds set a lower limit. On a 7,000 square foot lot that is 3,150 square feet for the house, drive, walks and patio together.
| Surface | Counts? |
|---|---|
| Concrete patio | Yes, 100% |
| Uncovered wood deck with gaps, over soil | 50% |
| Covered patio | As building coverage, 100% |
| Gravel over soil, landscaping or foot traffic only | No |
| Pool water surface | No (coping counts) |
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From the City of Austin Residential New Construction and Addition Permit Application (LDC 25-1-23 definition and worksheet).
Building a patio that lasts on Austin clay
Slope
About 1/4 inch per foot away from the house, the 2 percent the code asks for near a foundation (IRC R401.3). Water that pools against a slab foundation on clay is the last thing a house here needs.
Joints
NRMCA recommends joints about every 10 feet on a 4 inch slab, never more than 15, in near-square panels, so a 12x24 patio gets a joint across the middle.
Trees
Austin's tree rules allow no impacts in the inner quarter of a protected tree's critical root zone, no more than 4 inches of cut or fill in the half root zone, and keep half the full root zone undisturbed. Trees under 19 inches in diameter aren't regulated on residential property. A patio under a big live oak may need to shrink, move or become a deck.
Heat
Summer patios are poured early in the day and kept moist while they cure; the Texas heat guide explains why.
Patio add-ons
- A thickened, reinforced section for a hot tub
- A pad for an outdoor kitchen or smoker
- Steps down from the back door
- A walkway to the side gate or driveway
- An extension of an existing patio