The delivery-day protocol
Substitution is almost never discovered on a finished job, because finished joinery looks identical whichever grade of board is inside it. It is discovered two monsoons later when a bottom rail swells. The only reliable moment to catch it is the twenty minutes when the material is on the landing and not yet inside the flat.
- Ask for the challan before unloadingIt should name the brand, grade, thickness, sheet count and IS number. A challan that says 'plywood 19mm' and nothing else is a red flag on its own.
- Photograph the stack edge-onPly mill stamps run along the edge. One photograph of the stack captures twenty sheets of evidence.
- Spot-measure three sheetsA ₹400 vernier caliper. 19 mm ply should measure 18.4–19.2 mm. Under 18 mm is a different product sold as this one.
- Open one hardware cartonCheck the brand moulding on the hinge cup itself, not only the box. Boxes get reused.
- Count against the BOQQuantities delivered should reconcile with the quantity you are paying for. Short delivery is quietly common on running-foot items.
- Sign the challan with a note'Received subject to inspection' costs nothing and preserves your position for 48 hours.
What to look for, material by material
| Material | The mark to find | The quick test | Typical substitution |
|---|---|---|---|
| Plywood | IS:710 or IS:303 + mill name on the edge | Vernier the thickness; check core gaps at a cut edge | MR ply sold as BWR; 18 mm sold as 19 mm |
| Laminate | Brand and grade printed on the reverse | Vernier: 1 mm reads 0.92–1.05 mm | 0.8 mm supplied as 1 mm |
| Hinges / channels | Brand moulded into the metal, batch code on carton | Soft-close should stop a shutter without a bounce | Unbranded lookalikes in branded cartons |
| Quartz / granite | Slab number and quarry batch on the reverse | Water drop on an offcut: should bead, not darken | A different lot from the approved slab |
| Adhesive | Sealed tin, batch and expiry printed | Check the expiry — expired PVA fails at the glue line | Decanted or rebranded adhesive |
| Paint | Sealed tin with dealer sticker and shade code | Tin should be factory-sealed and machine-tinted | Hand-tinted shade close to the code |
| Aluminium sections | Anodising or powder-coat grade on the invoice | Micron thickness on the test certificate | Lower micron coating, fails near the sea |
Design and build under one accountable roof
The three payments that need a check attached
Most Mumbai contracts run a 4–5 tranche payment schedule. Two of those tranches should be conditional on material verification rather than on elapsed time: the material advance and the pre-installation release. Tie them in writing, and the entire supply chain behaves differently.
- Material advance (typically 30–35%): released on signed BOQ plus approved sample set, not before. The sample set is the physical record of what was promised.
- Delivery tranche (typically 25–30%): released against photographed challans matching the BOQ, with IS marks visible. This is the single most useful clause you can add to a contract.
- Installation tranche (typically 20–25%): released after hardware is fitted and demonstrated — every soft-close tested, every drawer pulled to full extension.
- Retention (5–10%): held 30–45 days past handover against the snag list. Do not let this be waived for a discount; it is the only leverage that survives handover.
What a substitution actually costs you
| Substitution | Saving to the contractor | Cost to you | When it shows |
|---|---|---|---|
| MR ply instead of BWP, kitchen carcass | ₹14,000–₹19,000 | Carcass replacement, ₹85,000+ | Monsoon 2–3 |
| 0.8 mm laminate as 1 mm | ₹6,000–₹9,000 | Edge chipping, visible wear | Month 8–18 |
| Unbranded soft-close hinges | ₹7,000–₹12,000 | Sagging shutters, no warranty claim | Month 10–24 |
| MS screws in place of SS | ₹900–₹1,800 | Rust bleed staining shutter faces | Monsoon 1 |
| Lower-micron anodising | ₹4,000–₹7,000 | Pitting on balcony frames | Year 2–3 near the coast |
Every figure is ex-GST and based on a typical 2BHK scope in Mumbai, 2026.
Nobody substitutes material on a site where the client opened the first carton.
Greenbox site lead
The checks that belong at fabrication, not delivery
Some quality problems are invisible in the raw material and obvious in the assembled unit. These need a second inspection window, ideally when the carcasses are built but before the shutters go on — usually around week four of a 2BHK joinery programme. At that point a carcass can still be corrected; a week later it is inside a laminated box.
- Look inside a carcass. Are the internal faces laminated or raw ply? A quotation that says 'inner laminate' and a carcass with raw ply inside is a ₹22–₹30 per sq ft difference you are paying for.
- Check the shelf spans. Any 19 mm shelf longer than 900 mm without a centre support will sag under books or steel utensils within two years. Ask for a mid support or 25 mm board.
- Count the dowels and confirm the joinery method. Butt-jointed and screwed, or dowelled and glued with a minifix? The second holds; the first racks.
- Test drawer runners loaded. Put 15 kg in a drawer and open it fully. A 45 kg-rated telescopic channel should not tilt or bind.
- Check the back panel thickness. Six mm is the minimum for a wardrobe; 3.5 mm backs bow and are a common quiet saving.
- Verify the hinge count. Two hinges on a 2,100 mm shutter is not enough; it needs four, and five above 2,200 mm.
These six checks take twenty-five minutes on site and are the highest-yield inspection in the entire project. Nothing about them requires technical training — only the willingness to open a carcass and load a drawer while the work is still accessible.
None of this requires suspicion as a posture. Most Mumbai contractors we work alongside supply exactly what they quoted, and the ones who do are usually pleased to be checked because it settles the question early and protects them from a later accusation they cannot disprove. The problem is not widespread dishonesty; it is that an unverified supply chain has no mechanism for catching an honest error either — the wrong pallet delivered, the substitute sent because the specified board was out of stock, the hardware shipped in a batch that was recalled. A photographed challan and an opened carton catch those too, and they catch them on the day they are still free to fix.
Selected work by Greenbox Design Studio. Tap any image to enlarge.
Frequently asked questions
What IS number should plywood carry?+
IS:710 for boiling-waterproof (BWP or marine) ply, and IS:303 for MR and BWR grades, with the grade printed alongside. The stamp runs along the sheet edge with the mill's name. Sheets with no edge marking should not be accepted regardless of what the challan says.
How do I know if hardware is genuine?+
Genuine Hettich, Hafele and Blum hardware carries the brand moulded into the metal component itself, plus a batch code and often a QR on the carton. Loose components in unmarked polythene are the clearest warning sign. All three brands let you verify a batch code through their India customer service.
Can I test materials myself without tools?+
Partly. A ply edge shows core gaps and overlaps to the naked eye; a good sheet has tight, even plies with no voids. Tap-testing a sheet gives a dull thud when the core is patched. But thickness and laminate grade need a ₹400 vernier caliper, which is worth owning for the duration of a project.
What if material has already been installed?+
Ask for the challans and photographs retrospectively; a legitimate contractor will have them. If they do not exist, negotiate an extended written warranty on the affected element rather than a dismantling exercise. Dismantling fitted joinery to verify a board grade usually costs more than the difference in dispute.
Should the client or the designer check materials?+
The studio should, and a good one documents it without being asked. But sign-off is yours, so attend at least the first two material deliveries. After that the supply chain knows the site is watched, which is most of the benefit.