I’m Brian Gillespie, founder of Concrete Contractor Magnolia. Homeowners in Montgomery County keep asking how to add usable square footage to the back patio without ripping out the old slab. Here’s the straight talk—no fluff—based on extensions we pour every week between FM 1488 and FM 1774.
1. Why Extend Instead of Replace?
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The existing slab stays in place, saving demolition fees.
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A doweled connection keeps the new work level long-term.
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You choose any finish—broom, stain, or stamp—to match the current surface.
Ready to visualize budget impact? Check the bar chart above for average cost per square foot by finish. A basic broom texture starts around $8.50 / sq ft; a stamped pattern reaches $12.00.
2. Measure First, Dowels Second
Grab a tape and mark the length you want off the original edge. My crew drills ⅝-inch holes every 24 inches, epoxies #4 rebar dowels, and ties rebar in a 16-inch grid. That mechanical tie-in stops future separation—no guessing.
Question: How many guests do you plan to seat? Use that headcount to set the new footprint.
3. Sub-Base and Compaction
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Excavate 6 inches below final grade.
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Spread 4 inches of #57 limestone.
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Compact to 95 % modified Proctor with a plate tamper.
Compaction equals longevity. No shortcut produces the same bearing capacity.
4. Formwork and Slab Thickness
We set 2 × 6 forms to achieve a true 4-inch slab while allowing 1 inch of surface drop for drainage. All forms sit on stakes outside the pour so there’s zero void under the finished edge.
5. Mix Design That Resists Magnolia’s Heat
Our ready-mix partner delivers 3,500 psi with a 0.45 water-cement ratio and a mid-range plasticizer. The blend hits a slump that flows around rebar yet cures strong even when summer highs reach 100 °F.
6. Placement, Screeding, and Bull Float
Concrete trucks back to the street; we chute into wheelbarrows to protect turf. After screeding we make one bull-float pass, embed aggregate, then wait for bleed-water sheen to fade before edging.
7. Finish Options at a Glance
| Finish | Texture Detail | Extra Cost vs. Broom |
|---|---|---|
| Broom | Straight-line traction | Base |
| Stained | Integral pigment + solvent sealer | +$2 / sq ft |
| Stamped | Ashlar or slate mat + release powder | +$3.5 / sq ft |
Choose the look you want; the structural prep stays identical.
8. Curing and Sealing Timeline
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Day 0–1: Leave forms until next morning.
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Day 2: Moist cure with wet burlap or apply curing compound.
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Day 7: Light foot traffic is fine.
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Day 14: Set furniture.
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Day 28: Drive lawn equipment or grills across the joint line.
9. Permits and HOA Approval
Magnolia requires a flatwork permit for extensions that tie into the primary slab. We handle paperwork and book the base and final inspections. HOAs such as Indigo Lake Estates often ask for color samples; our office keeps a binder ready to email.
10. Common Missteps You Can Skip
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Pouring without dowels—leads to trip lips in one season.
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Skipping compaction—slab settles when clay shrinks.
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Over-watering mix on-site—weakens surface paste and invites scaling.
11. Interactive Checklist Before You Call
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Final square footage calculated
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Utility locates requested
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Finish style picked from the chart above
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HOA form downloaded (if needed)
If you checked all boxes, you’re set for scheduling.
12. Rich Resources for DIY Research
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Detailed step sequence: Adding a Concrete Patio Extension to an Existing Patio in Magnolia, TX
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Direct quote or project walk-through: Contact our crew or call 713-681-4343.
I’ll answer, discuss your measurements, and lock a spot on the pour calendar—rain or shine.
