Calculate cubic yards, bags, and Gresham OR-accurate ready-mix costs for any Multnomah County project. Includes Oregon's 18-in. frost depth, wet PNW subgrade drainage guidance, and ORSC 2021 compliance notes.
Enter dimensions for volume, bags, and Gresham OR / Multnomah County material cost estimate.
Driveway: 4 in. min, 3,000–3,500 PSI per ORSC 2021. Gresham permit required. Dewater subgrade — never pour on wet OR saturated soil. 4–6 in. 3/4-in. crushed rock base. Drain away from structure. No air entrainment needed. Seal every 2–3 yrs.
Walkway 4 in · Driveway 4–5 in · Patio 4 in · Garage 4 in · Foundation 4–6 in · Footing 8–12 in · Retaining Wall 8–12 in
Gresham is Multnomah County's second-largest city — a Portland metro suburb of ~115,000 at the base of the Columbia River Gorge. Its concrete environment is defined by the Pacific Northwest's relentless wet season: 49+ inches of annual rainfall concentrated from October through April, native Gresham Series soils that are classified as somewhat poorly drained silty clay over weathered glacial till, and a mild but real frost exposure of 18 inches per ORSC 2021 / City of Gresham footing checklist. Unlike Midwest pages, Gresham does not require air-entrained concrete (oceanic Zone 9a climate, only 20–30 frost days/year). The dominant challenges are wet subgrade dewatering, proper drainage installation, and timing pours around the PNW rain calendar.
Gresham's combination of 49+ inches of annual rainfall and poorly drained native silty clay soils means subgrade is often wet, soft, or saturated for much of the year. Never pour concrete on wet or soft subgrade — water in the base mix compromises concrete strength and causes settlement and cracking. Before any Gresham concrete project: (1) dewater using a submersible pump, French drain, or perforated pipe system; (2) allow the base to dry until it passes the "thumb test" (no depression under firm thumb pressure); (3) compact crushed rock base to 95% Proctor. Budget for a French drain or perimeter drain at footing base — this is not optional in Gresham's wet PNW soils. Also ensure all flatwork surfaces drain away from structures at 1–2% minimum slope to prevent surface water infiltration.
All flatwork: 3,000 PSI min (ORSC 2021); 4 in. driveways/patios; no air entrainment required (PNW mild F0/F1) · Footings: 18 in. below grade min (Multnomah Co. frost depth — confirmed by Gresham Building) · Garage / interior slabs: 4 in. min, 6-mil vapor barrier per ORSC · Key PNW prep: Dewater subgrade, install French drain at footing base, use 4–6 in. compacted 3/4-in. crushed rock base · Slope: All exterior flatwork 1–2% away from structures · Control joints: Every 10 ft (10× thickness in feet) · Sealer: Penetrating silane/siloxane every 2–3 years · All OR contractors must hold valid Oregon Construction Contractors Board (CCB) License — verify at Oregon CCB.
Gresham's concrete pouring window is tightly constrained by PNW rain: May through September is ideal — rainfall drops significantly and temperatures stay above 50°F for reliable curing. October–April is possible but requires careful scheduling around rain events, protecting fresh concrete from rain for a minimum of 4–6 hours after finishing (rain can wash cement from fresh concrete surface), and monitoring subgrade drainage. ACI 308 wet-curing methods are naturally assisted by Gresham's ambient humidity — reduce water evaporation concerns but protect from actual precipitation. Book suppliers and contractors 2–4 weeks ahead for the June–August peak window.
Unlike northern and Midwest cities in this series, Gresham does not require air-entrained concrete. With only 20–30 frost days per year and a shallow 18-in. frost depth (Zone 9a oceanic), ACI 318 classifies Gresham as Exposure Class F0/F1 — negligible to mild freeze-thaw. Standard non-air-entrained 3,000–3,500 PSI concrete is ORSC-compliant for all exterior flatwork. This saves $5–$12/yd versus northern markets. Focus your specification attention on drainage, subgrade dewatering, and proper sloping — not air content or frost protection.
Multiply length × width × (depth ÷ 12) for cubic feet, divide by 27 for cubic yards, add 10% overage. Major Gresham / Portland metro suppliers include CalPortland, CRH (formerly Knife River), CEMEX, Pacific Ready Mix, and regional Multnomah County independents. Short-load fees run $100–$175 for under 3–5 cu yd. Schedule pours for dry weather windows — confirm a 24-hour dry forecast minimum before pouring any exterior flatwork.
Never pour concrete on wet, saturated, or soft subgrade in Gresham — always dewater and compact first. Install drainage at footing base. Always pull a permit — Multnomah County inspectors check subgrade preparation and footing depth. Verify all Oregon contractor licenses at Oregon Construction Contractors Board (CCB). Unpermitted work must be disclosed at sale in Oregon.
Multnomah County / Portland metro ready-mix pricing is above the national average — high Pacific Northwest labor costs, Portland metro demand, and regional material logistics push prices higher than Midwest or Southeast markets. No air-entrainment premium applies, but PNW labor and delivery costs are significant. Year-round suppliers available but peak-season (Jun–Aug) booking is recommended.
| Mix / PSI | Gresham OR Price / Cu Yd | National Avg | Best For | Air Entrained? | ORSC 2021 |
|---|---|---|---|---|---|
| 2,500 PSI — Light | $148–$160 | $130–$148 | Light interior slabs only | Not Needed | Below Flatwork Min |
| 3,000 PSI — OR Standard ✓ | $153–$168 | $143–$158 | Driveways, patios, walkways | Not Needed | Compliant |
| 3,500 PSI — Mid Strength | $160–$175 | $153–$166 | Pool decks, wet subgrade slabs | Not Needed | Compliant |
| 4,000 PSI — Structural | $168–$185 | $161–$173 | Foundations, structural slabs | Not Needed | Compliant |
| 5,000 PSI — Commercial | $182–$200 | $178–$193 | Commercial / engineered | Not Needed | Compliant |
| City | County / State | 3,000 PSI / Cu Yd | Frost Depth | Air Entrained? | Key Challenge |
|---|---|---|---|---|---|
| Gresham | Multnomah, OR | $153–$168 | 18 in. | Not Required | Wet PNW Subgrade |
| Portland | Multnomah, OR | $155–$170 | 18 in. | Not Required | Wet Subgrade |
| Seattle | King, WA | $165–$185 | 12 in. | Not Required | Wet/Clay Subgrade |
| Eugene | Lane, OR | $148–$163 | 12–18 in. | Not Required | Moderate Clay |
| Sacramento | Sacramento, CA | $160–$178 | 0–6 in. | Not Required | Adobe Clay / Heat |
The City of Gresham Building Division requires permits for new driveways, patio slabs, pool decks, foundations, and retaining walls. Apply at greshamoregon.gov/building-permits. Standard permits process in 3–7 business days. Inspectors verify frost depth (18 in.), subgrade preparation, and vapor barriers per ORSC 2021. Verify Oregon contractor licenses at Oregon CCB.