A plain‑English read of Dunaway's REV 3 structural plans for 25 Aria Isle Dr, Lot 4. What's different between the two new REV 3 option sets, what changed from REV 2 — and how many piles go where, how the fill pad gets built, and what each path costs.
If you read nothing else: REV 3 didn't redesign your house — it gave you a menu. Here's the short version of both comparisons.
The Helical Piles set and the Straight Shafts set are identical everywhere except one thing: how the foundation reaches load‑bearing ground. Helical = steel piles screwed in. Straight shafts = drilled concrete piers, 24″/36″ wide.
→ A pick‑one bidding choice — steel piles vs. drilled concrete piers — not two different designs.
REV 2 floated a structural slab over a 6″ void box. REV 3 sets the slab on the ground, over a 24″ engineered select‑fill pad. REV 3 also adds the straight‑shaft option. Piles, grade beams, and all framing are unchanged.
→ Same structure, a simpler & typically cheaper slab approach, plus a second option to price.
Both are REV 3, both 18 sheets. A page‑by‑page text comparison shows the only sheets that differ are the Foundation Plan (S1.0) and Foundation Details (S2.0) — and even there, only the deep‑foundation element changes.
Steel, screwed in. Designed & installed “by others” (the pile manufacturer). The plan lists two pile types by allowable working load — 30 & 50 kip — which, at the required 2× factor of safety, must each prove a minimum capacity of 60 & 100 kip. Embedment depth per the manufacturer's drawings. No spoils, fast, low vibration.
Concrete, drilled. Cast‑in‑place piers, 24″ dia. (typical) and 36″ dia. Reinforcing scales with diameter (12″→4‑#4 up to larger→6‑#6), #3 ties at 12″ o.c. Familiar to local concrete crews; generates spoils and needs stable, dewatered holes.
* Depth — confirm: the plan carries two figures — a Foundation‑Parameters note of 18 ft below natural grade (U.N.O.) and a stray callout reading “12/36 drilled pier, 15'‑0″ below grade.” That 15′ note still appears on the helical sheet too; ask Dunaway which governs.
This is a bid decision, not a design fork. Dunaway drew the same house two ways so you can price both trades and pick the better value/schedule. Helical leans on a specialty pile installer (US Helicals, Cantsink, Ram Jack); straight shafts lean on a drilled‑pier / concrete crew. The slab, grade beams, and the whole building above are the same either way.
You asked how many piles/piers and where. The honest answer: the same grid of points carries the house in both options — only the element at each point changes. The exact count and coordinates live on Dunaway's S1.0; the schematic below shows the pattern, not a survey.
Read it as the pattern, not the exact count. Deep‑foundation points sit under the grade beams — at every intersection, at the steel‑column lines, and at intervals along each beam. For a footprint this size (≈151′ × 90′ ≈ 8,500 sf), a linear‑foot estimate — ~1,125 ft of grade beam at 8–10 ft spacing plus corners and the column / pool / elevator points — lands around ~125 points (range ~95–160). The exact number and coordinates are on Dunaway's S1.0 and get finalized on the pile contractor's signed shop drawing.
Helical and straight‑shaft use the same points. Because the grade‑beam grid is identical between the two REV 3 sets, the number and locations don't change — only the element installed at each point does (a steel helical pile, or a 24″/36″ drilled concrete pier). So whichever trade you pick, they're building to the same layout. To get the exact count: ask Dunaway for the pile/pier tally on S1.0, or have each bidder mark it on their takeoff — that's the number that should drive pricing.
REV 2 (06/04/2026) was the previous plan — helical only, with a structural slab floated on a void box. Comparing it to REV 3‑Helical isolates exactly what Dunaway changed.
Suspended slab. A 6″ collapsible void box sits between slab and clay, so when the soil swells it crushes the void instead of pushing your floor up. The piles carry the structure. More conservative; more cost.
Ground‑supported slab. The void box is gone; the slab sits on a 24″ structural “select fill” pad (engineered, imported, compacted fill) over a 4″ leveling bed. Whether that 24″ requires excavating & replacing native soil or building a pad up on prepared subgrade is set by the geotech — confirm with Dunaway. Simpler, faster, typically cheaper than a void box.
Both designs answer the same problem — building on expansive Houston clay that swells and shrinks. REV 2 isolated the slab from the soil (void box); REV 3 conditions the soil instead (select‑fill pad) and sets the slab on it. The helical piles and grade beams are unchanged, so the building's structural backbone didn't move. A slab‑strategy change plus a new option — not a re‑engineering of the house.
A fair confusion: “engineered fill” isn't poured like concrete — it's earthwork, built up in thin layers before the slab. And it doesn't automatically mean digging out your dirt. Here's the real sequence on site.
Clear the building pad and remove organics / soft soil down to the depth the geotech report calls for. This is the step that may (or may not) mean over‑excavating native clay — the report decides.
Truck in lab‑approved “select fill” — soil chosen to a spec (a controlled, low‑plasticity gradation), not whatever is on site.
Place it in thin layers (“lifts”), typically 6–8″ at a time — you don't dump 24″ at once.
Roll each lift to a target density (e.g. ~95% Proctor). A testing lab signs off every layer before the next — this is the “subgrade / material testing” the plan defers to the geotech.
Repeat until the 24″ pad reaches design grade, then a final 4″ leveling bed to set the slab elevation.
Helical piles or drilled piers go through the pad to firm soil; then grade beams and the 4″ slab pour on top. The pad supports the slab; the piles carry the house.
Not automatically. The structural sheet only says “24″ structural select fill” and points to the geotech for the rest. On high‑plasticity clay, geotechs often do call for some over‑excavate‑and‑replace (sometimes deeper than 24″), but it can also be a built‑up pad on prepared subgrade. One clean question closes it: ask Dunaway / Quartet — “for the REV 3 select‑fill pad, how much native soil is removed vs. built up, and to what depth?” That answer also drives the dirt‑work cost.
Researched market ranges for the deep‑foundation element only (slab, pad, and grade beams cost roughly the same either way). These are sourced estimates, not bids — use them to frame the conversation, then have your bidders price Dunaway's exact pile/pier schedule.
On expansive clay with groundwater above 7 ft and a schedule‑sensitive steel frame, helical piles are typically both cheaper and faster — on the order of 40–55% less (≈$170k vs ≈$375k+ typical, before the casing & spoils adders groundwater triggers) and ~1–3 weeks faster net, mostly because there's no concrete cure and the steel frame can land the day piles finish. It flips toward drilled piers only if Dunaway uses large‑diameter shafts to cut the point count, the site can be kept dry/uncased, or per‑point loads exceed practical helical capacity.
Both estimates assume ~125 support points (range ~95–160) — from ~1,125 lf of grade beam at 8–10 ft spacing plus corners and the heavier column / pool / elevator points. That's the same ~125 points in the layout schematic above, whichever element fills them. Get the real count from Dunaway's S1.0, have each bidder price that exact schedule, and require the concrete bidders to quote dry vs. cased/slurry below 7 ft separately.
Estimates compiled from published 2024–26 market data (HomeGuide · TorcSill · Hubbell/CHANCE · Helical Pile World · Houston ready‑mix & Texas eng‑forum contractor data) — not quotes. Largest uncertainties: the structural 30–50 kip helical unit price and the groundwater casing premium. Bidders to price against — helical: TorcSill, US Helicals, Cantsink, Ram Jack Houston; concrete: Lane, DSD, Volcano.
A full text diff of all 18 sheets confirms the changes are surgical — confined to the Foundation Plan and Details. Everything below is identical across REV 2, REV 3‑Helical, and REV 3‑Straight.
All three sheets are stamped “Issued for HOA Permit Set — NOT for construction.” Before bidding, confirm: (1) the governing pier depth (18 ft vs. the stray 15′ note); (2) the select‑fill scope — remove‑and‑replace vs. built‑up, and to what depth; (3) the pile/pier count on S1.0; and (4) which option — helical vs. straight shaft — you'll build. Pile/pier sizing is still “designed by others.”