What a diagnostic inspection actually involves

“Free quote” and “diagnosis” are different products, and confusing them is the most expensive mistake in remedial procurement. A quote scoped from a walk-around is priced to protect the contractor from what they haven’t seen — padded, or primed for variations. A diagnostic inspection replaces that uncertainty with evidence before anyone commits to a number.

What actually happens on a diagnostic inspection

Desktop first. Drawings, previous reports, maintenance history, defect complaints mapped by location and date. Recurring leak reports on one stack tell an investigator where to look before anyone is on site.

Systematic visual survey. Every accessible element, not just the reported problem — defects photographed, located and tagged to a numbered schedule. The schedule is what makes the eventual scope priceable and comparable.

Targeted testing, chosen by hypothesis. Not every test on every job — the right ones for the suspected mechanism:

Test	What it establishes
Tap/hammer survey	Extent of drummy render, tiles, concrete delamination
Cover meter	Reinforcement depth — the single best predictor of corrosion risk
Carbonation depth	How far the concrete’s chemical protection has been lost
Chloride sampling	Whether patch repair can work at all, or protection systems are needed
Half-cell potential	Active corrosion zones invisible from the surface
Moisture mapping / ELD	Where water actually is, and where it’s entering
Pull tests	Whether anchors, balustrades and fixings hold their design loads
Investigation openings	Ground truth — the condition of what’s buried

Openings, honestly scoped. Some of the most valuable evidence requires lifting tiles or breaking out small areas. Good practice is representative sampling — enough locations to establish the pattern, reinstated cleanly, agreed in advance.

What the report should contain

A condition report worth paying for has: a defect schedule with locations and photographs; cause analysis (the mechanism, not just the symptom); extent mapping including tested-but-not-yet-visible deterioration; repair options at more than one intervention level with the trade-offs stated; risk ranking so urgent items are distinguishable from programmed ones; and budget guidance for each option.

If a report ends with a single number and no schedule, it’s a quote wearing a lab coat.

The economics of skipping it

The inspection is typically low single-digit percent of the works value it defines. Against that: scopes discovered mid-works reprice at variation rates, wrongly diagnosed causes buy repairs that fail (patching chloride-contaminated concrete, membraning over structural movement), and committees that fund works twice fund the second round with their credibility.

Diagnosis first isn’t a sales pitch for caution — it’s how the price you accept becomes the price you pay.

General information, not advice on a specific building. Inspection scopes vary with structure, age and reported symptoms.