Question 1

What is a concrete subcontractor agreement?

Accepted Answer

A concrete subcontractor agreement is a contract between a general contractor (or project owner) and a concrete subcontractor who will perform specific concrete work — foundations, slabs, flatwork, walls, columns, decorative concrete, or structural elements. The agreement governs the entire scope of concrete operations including site preparation, forming, reinforcement placement, concrete ordering and placement, finishing, curing, and post-pour protection. Unlike a general construction subcontract, a concrete-specific agreement addresses the technical and timing-critical nature of concrete work: mix design specifications, pour scheduling, weather contingencies, slump testing, cylinder break requirements, and the narrow windows between placement and finishing that make concrete one of the most schedule-sensitive trades on a construction project.

Question 2

What concrete mix specifications should the agreement include?

Accepted Answer

The agreement should specify the concrete mix design requirements for each application: minimum compressive strength (typically 3,000 PSI for residential slabs, 4,000-5,000 PSI for commercial, and higher for structural elements); slump range (typically 4-6 inches for standard placement, lower for slopes); maximum water-cement ratio; air entrainment percentage (critical in freeze-thaw climates — typically 5-7%); aggregate size and type; any admixtures (accelerators for cold weather, retarders for hot weather, plasticizers for pump placement); fiber reinforcement specifications if applicable; and the batch plant or ready-mix supplier to be used. The agreement should also specify who orders the concrete, who pays for it (if not the subcontractor), and the process for approving mix design changes during the project.

Question 3

How should pour scheduling and weather delays be handled?

Accepted Answer

Concrete placement is uniquely weather-sensitive — extreme heat accelerates curing and can cause cracking, cold weather slows strength gain and risks freeze damage, rain during finishing ruins surface quality, and wind causes rapid surface drying. The agreement should address: minimum and maximum temperature ranges for placement (ACI 306 guidelines for cold weather, ACI 305 for hot weather); the decision-making process for canceling or rescheduling pours due to weather (who makes the call, by what deadline, and who bears the cost of canceled ready-mix loads); hot weather and cold weather protection measures the subcontractor must implement (sunshading, windbreaks, insulated blankets, heated enclosures); and whether weather delays extend the contract timeline. Many agreements require the subcontractor to monitor forecasts and provide 48-hour written notice if weather conditions may affect a scheduled pour.

Question 4

Who is responsible for concrete testing and inspections?

Accepted Answer

Concrete testing and inspection responsibilities must be clearly assigned in the agreement. Typically, the general contractor or owner hires and pays for an independent testing agency (ACI-certified technicians) who perform field tests during placement — slump testing (ASTM C143), air content testing (ASTM C231), temperature measurement, and cylinder fabrication for compressive strength testing (ASTM C39) at 7 and 28 days. The subcontractor is responsible for cooperating with the testing agency, holding the pour if tests fail, and replacing any concrete that does not meet specifications — at the subcontractor's cost if the failure is due to their handling (adding water, improper vibration) or at the ready-mix supplier's cost if the batch was defective. The agreement should specify the number of test cylinders per pour volume, who receives the break reports, and the process for resolving disputes when tests fail.

Question 5

What warranty should a concrete subcontractor provide?

Accepted Answer

Concrete warranties are nuanced because not all defects are attributable to the subcontractor's workmanship. A typical concrete subcontractor warranty covers: workmanship defects (improper finishing, inadequate curing, poor joint placement, reinforcement misplacement) for 1-2 years; structural integrity per the design specifications; and compliance with the specified mix design and placement procedures. The warranty typically excludes: cracking due to design deficiencies (insufficient reinforcement, improper joint spacing designed by the engineer); settlement cracking caused by inadequate soil preparation (if soil prep was another party's responsibility); surface discoloration from calcium chloride or other additives specified by the owner; damage from premature loading or traffic on uncured concrete; and normal hairline shrinkage cracking. The agreement should clearly state what constitutes a warranty claim versus normal concrete behavior.

Question 6

How are change orders handled in concrete subcontracting?

Accepted Answer

Change orders in concrete work are common and can be extremely costly if not managed properly. The agreement should establish: a written change order process (no verbal approvals for additional work); pre-authorization requirements with a not-to-exceed amount before work begins; pricing methodology for changes (unit prices per cubic yard, per linear foot of forming, per square foot of flatwork); time extension provisions when changes affect the pour schedule; the impact of design changes on previously placed concrete (if a structural engineer changes reinforcement after forms are set, who pays for rework); and a deadline for submitting change order pricing (typically 5-10 business days after receiving the change directive). For concrete work specifically, the agreement should address standby time — if the subcontractor's crew and equipment are idle because the general contractor is not ready for a scheduled pour, the standby cost should be a pre-agreed daily rate.

Question 7

What insurance does a concrete subcontractor need?

Accepted Answer

Concrete subcontractors should carry: commercial general liability insurance ($1 million per occurrence / $2 million aggregate minimum, with many general contractors requiring $5 million for commercial projects); completed operations coverage (critical because concrete defects often manifest months or years after placement — delamination, spalling, structural cracking); workers' compensation insurance at statutory limits (concrete work is high-risk — back injuries, silica exposure, crush injuries from forms); commercial auto insurance for concrete trucks, pump trucks, and crew vehicles; inland marine or equipment floater coverage for owned equipment (power trowels, laser screeds, pump trucks); and umbrella/excess liability coverage ($5-10 million depending on project size). The agreement should require the subcontractor to name the general contractor and project owner as additional insureds and provide certificates before mobilizing to the site.

Question 8

What are the lien rights for concrete subcontractors?

Accepted Answer

Concrete subcontractors have mechanics' lien rights in all 50 states, but the procedures vary significantly. In many states, subcontractors must file a preliminary notice within a specific timeframe after first furnishing labor or materials (20 days in California, 45 days in Arizona, no requirement in some states). The agreement should address: preliminary notice requirements and who is responsible for filing; lien waiver exchanges — the general contractor typically requires conditional lien waivers with each progress payment and unconditional waivers for previous payments; the impact of joint check agreements (where the general contractor pays the concrete subcontractor and the ready-mix supplier jointly); and stop notice rights if the subcontractor is not being paid. The agreement should not contain a blanket lien waiver that waives the subcontractor's rights before they are earned — such provisions are void and unenforceable in many states.

Question 9

How should reinforcement and formwork responsibilities be allocated?

Accepted Answer

The agreement must clearly define which party provides and installs reinforcement (rebar, wire mesh, post-tension cables) and formwork (wood forms, steel forms, ICF systems). In some arrangements, the concrete subcontractor handles everything from excavation through finishing — a turnkey concrete scope. In others, the reinforcement is installed by a separate rebar subcontractor, the formwork is built by carpenters, and the concrete subcontractor only handles placement, finishing, and curing. The agreement should specify: who supplies and installs rebar (including size, spacing, lap lengths, and cover depths per the structural drawings); who provides and sets formwork (including alignment tolerances, form oil, and stripping schedules); who installs embedded items (anchor bolts, sleeves, conduit, waterstops); inspection requirements before the pour (rebar inspection by the structural engineer or special inspector); and responsibility for form blowouts during placement.

Question 10

What safety requirements apply specifically to concrete work?

Accepted Answer

Concrete work carries specific OSHA safety requirements beyond general construction safety. The agreement should address: silica exposure compliance (OSHA's respirable crystalline silica standard, 29 CFR 1926.1153, limits exposure to 50 micrograms per cubic meter — concrete cutting, grinding, and demolition generate significant silica dust); formwork and shoring requirements (OSHA 1926.703 requires forms and shores to support all loads without failure, with a safety factor of at least 2:1); concrete buckets and pump operations (proper rigging, exclusion zones during crane-bucket placement, pump line securing); personal protective equipment (rubber boots, gloves, and eye protection due to concrete's highly alkaline pH of 12-13, which causes chemical burns); confined space entry procedures for work in deep foundations, manholes, or tanks; and trenching and excavation safety for footing work (sloping, shoring, or trench box requirements per soil classification). The subcontractor should provide a site-specific safety plan before starting work.

Component	Purpose	Key Details
Scope of Work	Defines all concrete operations included	Forming, rebar, placement, finishing, curing, joint cutting, form stripping, embedded items
Mix Design	Sets technical concrete specifications	PSI requirements, slump, air entrainment, w/c ratio, admixtures, aggregate type, batch plant
Pour Schedule	Manages timing-critical operations	Pour sequence, coordination with other trades, weather contingencies, pump truck scheduling
Testing & Inspection	Ensures structural compliance	Slump tests, air tests, cylinder breaks at 7/28 days, rebar inspections, special inspections
Payment Terms	Structures compensation	Unit prices, progress payments, retainage, lien waivers, back-charge procedures
Insurance	Allocates risk and liability	GL, completed operations, workers' comp, auto, umbrella, additional insured requirements
Warranty	Defines post-completion obligations	Workmanship warranty period, exclusions for design defects, normal cracking, settlement
Change Orders	Manages scope modifications	Written authorization, unit price schedule, standby time costs, time extensions

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What Is a Concrete Subcontractor Agreement?

Mix Design Control

Lien Protection

Testing & QC

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Concrete Subcontractor Agreement

Key Components

How to Create a Concrete Subcontractor Agreement

Define the Concrete Scope

Specify Mix Designs and Materials

Establish the Pour Schedule and Weather Protocol

Set Testing and Inspection Requirements

Structure Payment and Lien Protections

Address Insurance, Warranty, and Dispute Resolution

Frequently Asked Questions

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