Question 1

What ACI standards apply to a concrete subcontract?

Accepted Answer

ACI 318 (Building Code Requirements for Structural Concrete) is the governing design code incorporated by reference into the International Building Code and most state building codes — the subcontract should require compliance with the edition in effect on the project's plan set date. ACI 301 covers specifications for structural concrete, ACI 117 sets placement tolerances (e.g., floor levelness F-number tolerances), ACI 305 governs hot-weather concreting, and ACI 306 governs cold-weather concreting (minimum 50°F placement, protection schedule). ACI 347 governs formwork design and stripping. The subcontract should list the specific ACI standards and editions that apply, require the sub's superintendent to hold an ACI Concrete Field Testing Technician Grade I certification, and require mix designs and submittals for review before pouring.

Question 2

How should rebar placement be specified?

Accepted Answer

Rebar placement must follow the structural drawings, ACI 318 cover requirements, and ACI 117 tolerances. The subcontract should require the sub to perform a pre-pour inspection in the presence of the prime's superintendent and the structural engineer's special inspector (when required under IBC Chapter 17), document placement with photos of bar size, spacing, lap lengths, and clear cover before concrete is poured, and stop the pour if deficiencies are identified. Grade 60 reinforcement meeting ASTM A615 is the default unless plans specify Grade 40 or epoxy-coated bars. For seismic design categories D/E/F, the sub must use ASTM A706 or A615 with supplementary requirements for weldability and ductility. Misplaced rebar is a constructability defect that often results in saw-cut repair, epoxy-dowel retrofit, or partial demolition — allocating this cost is a key subcontract risk.

Question 3

When can forms be stripped after a concrete pour?

Accepted Answer

Form-removal timing is governed by ACI 347R and the structural engineer's specifications. For non-load-bearing vertical forms (walls, columns, sides of beams), forms can be stripped when the concrete has reached sufficient strength to prevent damage (typically 12-24 hours after placement, faster in warm weather). For load-bearing horizontal forms (slab soffits, beam bottoms), forms must remain in place and reshoring must be used until the concrete has reached the specified design strength — usually confirmed by compressive strength testing of field-cured cylinders per ASTM C31 at 7, 14, and 28 days. The subcontract should require the sub to follow the project-specific form-removal schedule in the specs, maintain a cylinder testing log, and not strip forms until field-cylinder breaks confirm adequate strength. Premature stripping causes cracking, deflection, and potentially catastrophic collapse.

Question 4

What cold-weather protection is required?

Accepted Answer

ACI 306.1 defines cold-weather concreting as any three-day period with ambient temperature below 40°F. The subcontract should require the sub to maintain concrete temperature above 50°F for the first 7 days after placement, use heated water and aggregates when ambient falls below 40°F, insulate forms and surfaces with blankets or straw-and-plastic, monitor concrete temperature with maturity meters or embedded thermocouples, avoid placing on frozen subgrade, and delay finishing operations until bleed water fully disappears. Failures from inadequate cold-weather protection — frozen concrete, delayed strength gain, surface scaling — typically require removal and replacement of the affected pour, a cost that can exceed $50,000 on a large slab. The subcontract should assign cold-weather protection responsibility squarely to the sub and require advance notice of cold-weather pours.

Question 5

What curing is required after placement?

Accepted Answer

ACI 308.1 specifies curing requirements. Standard curing requires maintaining moisture and temperature for 7 days after placement for Type I/II cement or 3 days for Type III. Wet curing methods include continuous sprinkling, wet burlap, ponding, or soaker hoses. Membrane curing uses ASTM C309 curing compound applied immediately after finishing. For high-performance concrete (HPC) and bridge decks, curing may be specified for 14 days. The subcontract should require the sub to submit a written curing plan, apply curing within 30 minutes of finishing on exposed surfaces, document curing methods in daily reports, and repair any surface defects caused by inadequate curing. Plastic shrinkage cracks, dusting, and low surface strength are typical failures from short curing.

Question 6

What insurance is required for concrete pumping?

Accepted Answer

Concrete pumping has specialized insurance requirements beyond standard CGL. The subcontract should require a pumping sub to carry CGL of at least $2M per occurrence / $4M aggregate, auto liability of $1M CSL, pumper boom and equipment floater coverage at replacement value, and an umbrella policy of $5M-$10M. ACPA (American Concrete Pumping Association) certification should be required for operators. OSHA 29 CFR § 1926 Subpart Q governs concrete and masonry construction; pump operators must have clear radio communication with the placement crew and a 'spotter' between the truck and the placement area. Pump-boom strikes on overhead power lines are a catastrophic risk that drives the high insurance limits — a single incident can cost $10M in fatality claims. The prime should be named as additional insured on a primary, non-contributory basis.

Question 7

What OSHA standards apply to concrete work?

Accepted Answer

OSHA 29 CFR § 1926 Subpart Q (§§ 1926.700-1926.706) governs concrete and masonry construction. Key requirements: reinforcing-steel impalement protection (caps on exposed rebar ends whenever workers are at any elevation where impalement is possible, § 1926.701(b)); no worker under concrete being lifted until it is secured in place (§ 1926.701(d)); formwork designed per ACI 347 and removed only after adequate strength is confirmed (§ 1926.703); shoring designed by qualified person, inspected before each pour (§ 1926.703(e)); lockout/tagout on concrete mixers during maintenance (§ 1926.702); PPE including hard hats, safety glasses, and chemical-resistant gloves for handling fresh concrete (concrete burns are a frequent injury). The subcontract should require the sub to maintain an OSHA-compliant safety program and produce Form 300 logs upon request.

Question 8

What placement tolerances apply?

Accepted Answer

ACI 117 establishes tolerances for cast-in-place concrete. Typical values: foundation and footing plan location ±1 inch, elevation ±3/4 inch; column plumb ±1/4 inch per 10 feet with a maximum of 1 inch; slab flatness and levelness measured by F-number system (F_F / F_L) with typical ranges F_F 25-35 and F_L 20-25 for conventional slabs, F_F 50+ and F_L 35+ for super-flat warehouse slabs; embedded items (anchor bolts, sleeves) location ±1/4 inch horizontally and ±1/2 inch vertically; cover over reinforcement as specified ±3/8 inch. The subcontract should reference the project-specific tolerance requirements in the specs, require the sub to confirm tolerances before stripping forms, and specify corrective action (grinding, chipping, leveling compound) for out-of-tolerance work. F-number measurements must be taken within 72 hours of slab placement by a trained technician.

Question 9

How are concrete change orders handled?

Accepted Answer

Field conditions frequently require concrete changes: increased thickness for a slab-on-grade due to poor subgrade; additional reinforcement for revised structural loads; mix design changes for HPC or lightweight; weather-related delays and protection. The subcontract should require all changes to be authorized in writing before the work is performed, specify unit prices for common changes (cubic yard of 4000 psi concrete, ton of rebar, hour of crew time) in the subcontract Exhibit B, require time-and-material documentation for unpriced changes, and prohibit field-verbal authorization. T&M change orders typically include a 15-20% markup for overhead and profit. The pay-when-paid clause should apply to change orders the same as base contract amounts.

Question 10

What lien waivers are required on concrete subcontracts?

Accepted Answer

Concrete subs have strong lien rights because concrete is a core improvement to real property. The prime should require a conditional progress lien waiver with each progress payment (signed when the sub invoices but effective only upon payment clearing the bank), a final conditional lien waiver at substantial completion, and a final unconditional lien waiver at retainage release. California Civil Code §§ 8132-8138 requires statutory-form waivers. Texas Property Code Chapter 53 has a different statutory form. Florida Statutes § 713.20 has yet another. Using the wrong state's form renders the waiver ineffective. The sub should also provide preliminary 20-day notices where required (California, Nevada, Arizona) to preserve lien rights, even though the prime would prefer the sub not file liens. The subcontract should require the sub to list lower-tier suppliers (ready-mix suppliers, rebar suppliers, pump operators) and procure conditional waivers from them before each payment to the sub.

Question 11

What special inspection is required on structural concrete?

Accepted Answer

IBC Chapter 17 requires special inspection for structural concrete on most commercial and multifamily projects. The owner or design professional retains an ICC-certified special inspector (often a testing lab) to observe: rebar placement before each pour, concrete sampling and cylinder casting per ASTM C31, slump and air-content testing per ASTM C143 and C231, and concrete placement and consolidation. The special inspector reports to the building official. The subcontract should require the concrete sub to give 48-hour advance notice of each pour, cooperate with the special inspector, stop the pour if the inspector identifies deficiencies, and bear the cost of re-inspection if its work causes a failed inspection. Special inspection fees are typically an owner cost but re-inspection fees for sub-caused failures are back-charged to the sub.

Question 12

What warranty and defect remediation applies?

Accepted Answer

Concrete work is typically covered by a one-year warranty against defective materials and workmanship running from substantial completion, plus the state statute of repose for construction defects (6-15 years depending on state — California Code of Civil Procedure § 337.15 is 10 years). Common defects: surface scaling from inadequate curing or freeze-thaw, cracking beyond ACI 224R limits, low compressive strength from field-cylinder breaks, out-of-tolerance placement, and spalling from exposed or corroded rebar. The subcontract should require the sub to repair defects at its own cost during the warranty period (with minor exceptions for wear-and-tear and owner damage), allow the prime to cover costs and back-charge if the sub fails to respond within 10 days of notice, and survive as to latent defects until the statute of repose expires. Material manufacturer warranties for sealers and coatings should be delivered to the owner through the sub and the prime.

Concrete Subcontractor Agreement

What Is a Concrete Subcontractor Agreement?

When to Use a Concrete Subcontractor Agreement

Key Provisions

Scope & mix designs

ACI 318 compliance

Rebar placement

Progress billing

Insurance

Lien waivers

OSHA Subpart Q

Warranty & defects

Legal Considerations

Concrete-Specific Issues

How to Fill Out the Agreement

Identify the parties and project

Scope of concrete work

Progress billing and retainage

Insurance and pumping coverage

Lien waivers

Schedule and weather protection

Warranty and special inspection

Sign and retain records

Frequently Asked Questions

Create your concrete subcontract in under 10 minutes.

Concrete Subcontractor Agreement

What Is a Concrete Subcontractor Agreement?

When to Use a Concrete Subcontractor Agreement

Key Provisions

Scope & mix designs

ACI 318 compliance

Rebar placement

Progress billing

Insurance

Lien waivers

OSHA Subpart Q

Warranty & defects

Legal Considerations

Concrete-Specific Issues

How to Fill Out the Agreement

Identify the parties and project

Scope of concrete work

Progress billing and retainage

Insurance and pumping coverage

Lien waivers

Schedule and weather protection

Warranty and special inspection

Sign and retain records

Frequently Asked Questions

Related Documents

Subcontractor Agreement (Hub)

Construction Subcontractor

Lien Waiver

Mechanic's Lien

Construction Contract

Create your concrete subcontract in under 10 minutes.