How to Audit a Subcontractor's Work

Most construction work is delivered by subcontractors, so a main contractor's quality depends heavily on the quality of its subcontractors. Auditing a subcontractor's work — checking not just the output but whether their processes and records meet the required standard — is how you catch problems early, drive improvement, and protect yourself contractually. It's different from simply inspecting their finished work.

This article explains how to audit a subcontractor's work.

Inspecting vs auditing a subcontractor

Inspecting checks the physical work they've produced. Auditing goes further: it examines whether the subcontractor's processes, competence, records, and compliance are adequate and being followed. An audit might pass the visible work but flag that the subcontractor has no records proving concealed work was checked — a problem an inspection alone wouldn't reveal.

Audit against the agreed requirements

You can only audit against a standard that was agreed up front. Before you audit, be clear on:

• The scope of the subcontract works.
• The specification and drawings that apply.
• The quality requirements and ITPs.
• The records the subcontractor is contractually required to produce.

If these weren't defined at procurement, auditing becomes a negotiation rather than a check — which is why getting requirements into the subcontract matters.

What to examine

A subcontractor audit typically looks at:

• The work itself — sampled against the specification and drawings.
• Records — inspection sheets, test certificates, sign-offs, material certificates.
• Process compliance — are they following their method statements and the agreed ITPs?
• Competence — are operatives appropriately qualified for the work?
• Materials — correct, certified, and controlled.
• Open items — are previous defects and NCRs closed?

The emphasis on records is what makes it an audit: you're checking the evidence trail, not just the surface.

Sample, don't check everything

Auditing isn't 100% inspection — it's sampling to test whether the system is sound. Pick a representative range of work and records. If the sample is clean, confidence is high; if the sample reveals gaps, that's a signal to widen the audit and address the underlying process.

Be objective and factual

Audit findings should be factual and tied to the requirement, just like inspection findings: state what you observed, the requirement it relates to, and the evidence (or its absence). "No pre-pour inspection record exists for foundation pour F12, required by ITP-03" is actionable and defensible. Keep it about the work and the system, not personalities.

Drive corrective action

The output of an audit is a set of findings with corrective actions — fix the specific issues and, where a process failure is found, fix the process. Agree owners and dates, and verify closure. An audit that produces findings no one actions achieves nothing.

Use it to inform future work

Subcontractor audits are also management information. Patterns across audits tell you which subcontractors are reliable and which need closer supervision or shouldn't be re-engaged. Over time this sharpens your supply chain.

How software helps

Because subcontractor audits feed on records, having inspections and quality records in one digital system makes auditing dramatically easier — you can see at a glance which inspections happened, what they found, and whether findings were closed, rather than requesting paper files from the subcontractor. The audit findings themselves are then captured, assigned, and tracked to closure in the same place.

Key takeaways

Auditing a subcontractor's work checks their processes, records, and compliance — not just the finished output. Audit against requirements agreed in the subcontract, examine work and the evidence trail by sampling, write factual findings tied to the standard, drive verified corrective action, and use the results to manage your supply chain. Good records make it possible.