Introduction

You priced the job on brand A. A pallet turns up with brand B. The sub shrugs, the merchant says “equivalent”, and you’re stuck in the middle. Unauthorised material swaps cost you hours, trigger callbacks, and dent client trust. This guide shows what to lock down, how to block “like-for-like” surprises, and what to do when a swap slips through. You’ll get practical, field-tested controls= you can install this week—plus a quick way to capture specs and client acceptance so you’re protected before the first box lands on site.

Table of Contents

• Key Takeaways
• The Material Swap Problem
• Lock The Spec Before Work Starts
• Control Deliveries At The Door
• Manage Subcontractor Swaps
• Document On Site, Prevent Repeat Issues
• Frequently Asked Questions
• Conclusion

Key Takeaways

• Unapproved substitutions commonly add one to three extra site visits and two to six labour hours—small jobs feel it the most.
• Many contractors find mislabelled or “equivalent” deliveries crop up at least monthly when the pipeline is busy—delivery checks stop most of them at the door.
• In general, clear, signable specs cut swap disputes dramatically because everyone sees brand, model, colour, and critical performance in writing.
• Contractors often report that restocking and redelivery can swallow half a day’s profit; a simple three-point intake check avoids most returns.

The Material Swap Problem

Unauthorised swaps show up as different brands, downgraded grades (paint sheen, board thickness), or missing performance attributes (fire rating, moisture resistance, corrosion class). They look minor until warranty or compliance bites.

Why It Matters

• Performance gaps: A 12.5 mm board swapped for 9.5 mm, or exterior fixings delivered in the wrong corrosion class, lead to failures later.
• Compliance risk: Fire-rated, moisture-resistant, or certified potable-water components aren’t “equivalent” unless specified as such.
• Margin hits: In general, one swap means extra trips for returns, re-picks, and rework, adding two to six hours and delaying the programme by a day.

Example

A bathroom refurb priced on moisture-resistant plasterboard receives standard boards. The crew installs two walls before spotting the stamp. Result: strip-out, disposal, re-delivery, and a fresh start—two extra days and a dent in client confidence that lingers through handover.

Lock The Spec Before Work Starts

Stop swaps at the source with a spec that’s crystal clear and signed before materials move.

Build A Spec That’s Hard To Misread

• Name the exact product: brand, series, model/SKU, colour/finish, size, and critical attributes (fire rating, IP rating, moisture class, corrosion class, warranty).
• State acceptable alternatives: “Pre-approved equals only: [brand/model list]. Anything else requires written approval.”
• Add photos: front-of-box, label, and any certification marks.

Practical Detail

• For valves and fittings, include material (e.g., DZR brass) and connection type; for boards, thickness and rating; for fixings, diameter, length, and corrosion class.
• For paints, include system (primer, coats), sheen, base, coverage, and batch note (“single-batch supply to avoid shade variation”).

Get It Signed, Not Just Sent

• Use a signable proposal with the spec baked in. When the client signs, “equivalent” talk later has less room.
• With Donizo, you can capture the spec by voice on site, drop in photos of the exact products, generate a branded PDF proposal, and send it for e‑signature. Once accepted, you’ve got a clear, legally binding acceptance of the spec. If you’re supplying materials, you can later convert the accepted proposal to an invoice in one click.

Example

On a kitchen fit, you dictate into Donizo: “Appliance isolators: Schneider ‘Lisse’, 20A DP, white, model GGBL2020D, x4.” You snap a photo of the label and faceplate. The signed proposal references the exact SKU. When a different plate turns up, the merchant swaps it without debate because the paperwork is precise.

Control Deliveries At The Door

Most swaps are caught—or missed—during intake. Treat the doorstep like a quality gate.

The Three-Point Intake Check

1. Count: Boxes and units match the delivery note.
2. Code: SKU/model on each box matches your spec.
3. Critical attributes: Spot-check stamps and labels (e.g., moisture-resistant board stamp, IP rating on lights, corrosion class on fixings, fire rating on doors).

• Commonly, this five-minute check avoids a half-day wasted on returns and resets.

Mark And Park

• Label approved stacks with a bold marker: “OK – Spec Match – [date] – [initials].”
• Quarantine suspect items with tape and a “Hold – Await Approval” note to stop accidental installation.

Example

A merchant delivers 30 sheets of plasterboard. Intake check finds five standard boards mixed into a moisture-resistant batch. They’re ring-fenced immediately, driver notes the issue, replacement scheduled on the same run. No rework, no delays.

Quick Comparison

Manage Subcontractor Swaps

Subs often “make it work” under time pressure. That’s great for productivity, terrible for spec drift if uncontrolled.

Set A Hard Rule: No Swaps Without Approval

• Include a clear clause in your work order: “No substitutions without written approval. Unapproved swaps removed and replaced at subcontractor cost.”
• Define a fast path for approvals: one message with product label photo and datasheet link.

Hold Points That Matter

• Pre-install check for critical items: waterproofing systems, structural fixings, fire doors, electrical accessories in kitchens/bathrooms.
• Short photo submission before closing up: Many contractors find two or three “hold points” per small job prevent most expensive callbacks.

Example

Your electrician proposes an alternative downlight because stock ran out. They send a label photo and IP rating. You compare cut-out size, IP rating, and bezel finish to the spec. It’s a match; you approve in minutes. If the cut-out or IP rating differs, it’s a no.

Document On Site, Prevent Repeat Issues

Good documentation turns one bad delivery into a system improvement.

Photograph And Log Critical Items

• Snap deliveries of: boards with rating stamps, fixings (box labels), adhesives/sealants (batch and expiry), electrical accessories (model and rating), valves/fittings (material and WRAS-type marks where relevant).
• In general, keeping these photos with the job record shortens any dispute with suppliers to a single email.

Batch, Expiry, And Storage

• Adhesives, sealants, and compounds: log batch and expiry; rotate stock so “soonest expiry” gets used first.
• Store boards flat, fixings dry, and paints in temperature-stable areas; many failures trace back to site storage rather than the product itself.

When You Discover A Swap Mid-Install

• Stop. Isolate the area. Photograph what’s in place and what’s left in boxes.
• Notify the supplier and client with the photos and the signed spec extract.
• Decide: remove and replace or, if performance truly matches and the client agrees in writing, keep and log the change.
• Contractors often report that acting within the same day avoids schedule creep; leaving it “to sort later” stretches into a week.

Example

A concealed cistern arrives without the specified service valve assembly. You halt, photograph the box and part list, and send a side-by-side of the spec page. Merchant agrees to courier the correct valve by 10:00 the next day. Install resumes without opening tiles twice.

Frequently Asked Questions

What Counts As A Critical Spec And What Can Be Flexible?

Critical specs affect safety, compliance, durability, or visible finish: fire ratings, IP ratings, moisture classes, structural fixings, potable-water components, thickness, colour/finish, and interface dimensions (cut-outs, centres). Flexible items are usually hidden ancillaries where performance is identical and certified—still get written approval if in doubt.

How Do I Handle A Client Who Wants Cheaper Alternatives Mid-Job?

Price the alternative properly and state the impact. Provide the exact model/SKU and note any warranty or performance differences. Get a signed variation or updated acceptance. With Donizo, you can generate a fresh proposal section from voice notes and photos, send it for e‑signature, and keep the paper trail tidy before proceeding.

How Do I Prove A Supplier Sent The Wrong Product?

Photograph the delivery on arrival: labels, stamps, and quantities. Keep the delivery note. A side-by-side of your signed spec (brand/SKU) and the box label typically settles the issue quickly. In general, suppliers respond faster when they see clear label photos and the relevant spec line in one message.

Is An “Equivalent” Ever Acceptable?

Yes—if it truly matches performance, dimensions, visible finish, and certifications. Compare datasheets and confirm with the client in writing. Record the change and keep product photos. If any one of those attributes differs (e.g., cut-out size, IP rating, corrosion class), it’s not equivalent for your job.

What’s A Simple Wording To Block Unauthorised Swaps?

“Materials shall be as specified by brand and model. Acceptable equals are limited to [list]. No substitutions without written approval. Unapproved substitutions will be removed and replaced at supplier/subcontractor cost.”

Conclusion

Material swaps don’t have to drain your week or your profit. Lock the spec in writing with exact brands and SKUs, catch problems at the door with a quick intake check, enforce a clear “no swaps without approval” rule, and document the critical items with photos. Do this and most “equivalent” debates vanish before they start. If you want the fast, practical way to capture specs and get clean acceptance, use Donizo to dictate the spec with photos, generate a professional proposal, and secure an e‑signature. When the client says yes, you can turn that into an invoice in one click—less back-and-forth, more time on tools.