How to write an ITP (Inspection & Test Plan)

Published 6 July 2026 · VariationFlow

A practical guide to building an Inspection and Test Plan for a subcontract package: the anatomy of an ITP, how to sequence checkpoints, writing acceptance criteria, choosing hold, witness, surveillance and review points, and a worked example.

An Inspection and Test Plan (ITP) is the document that governs how your work is checked as it is built. A good one gets your work signed off cleanly and speeds up your handover; a vague one leaves you re-opening finished work to prove it was right. This guide covers how to write one that actually works on site.

What an ITP is for

An ITP breaks a package of work into its distinct activities, in the order they happen, and against each one it states how the work is checked, what "acceptable" means, who has to be involved, and what evidence is kept. It is both a plan (agreed before work starts) and a record (signed off as work proceeds). The main contractor usually reviews and accepts your ITP before you begin.

The anatomy of an ITP

Most ITPs are a table. Each row is a checkpoint, and the columns capture everything needed to inspect it. A workable set of columns:

• Activity / stage: the item of work being checked, in build sequence.
• Inspection or test: what is actually done to check it (visual, dimensional, a specific test, a reading).
• Acceptance criteria: the standard the work must meet, with the number or tolerance where there is one.
• Reference: the drawing, specification clause or standard the criteria come from.
• Point type: hold, witness, surveillance or review (see below).
• Responsibility: who inspects and who signs.
• Record: the evidence produced (a signed check, a photo, a test certificate, a reading).

Choosing the point type

Every checkpoint is classified by how much it interrupts the work. The common four:

• Hold point (H): work must stop and cannot proceed until the nominated party has inspected and signed off.
• Witness point (W): the other party is invited to attend, but work may proceed if they choose not to.
• Surveillance point (S): a routine in-process check by your own team, monitored rather than gated.
• Review point (R): a document or record is reviewed (a test certificate, a material cert) rather than a physical inspection.

Use hold points sparingly and deliberately, every one is a genuine stop that can hold up the programme, so reserve them for the moments where a defect would be buried or dangerous if missed (before a pour, before something is covered up, before energisation).

Writing acceptance criteria that work

The most common ITP failure is a criterion that cannot be judged. "Good workmanship" is not a criterion; "fixings at 1.5m centres maximum, to drawing E-204" is. Wherever a number, tolerance or named standard exists, put it in. If the acceptance criterion is a judgement, say whose judgement and against what reference. An inspector should be able to stand at the work with your ITP and give an unambiguous pass or fail.

A worked example

A containment installation might read: (1) Route and fixings, dimensional check, fixings at 1.5m centres to DWG-E-204, surveillance, photo. (2) Segregation from other services, visual, 300mm from other trades per spec 2.4, surveillance, photo. (3) Earth continuity, test, less than 0.05 ohm to BS 7671, witness point, reading plus photo. (4) Final installation, visual, complete and undamaged, hold point before ceilings close, signed off with photos. Four checkpoints, one genuine hold point, every criterion measurable.

From plan to record

An ITP only earns its keep when it is signed off as work proceeds, with evidence attached to each checkpoint. On paper, that means a clipboard in a site cabin and photos stranded on phones, and a hold point that can sit unsigned for days while a fitter waits. Captured digitally, each checkpoint is signed the moment the work is done, the photos and readings are attached to the row, and a completed ITP drops straight into the handover pack with nothing to reassemble.