What is actually in the coat build-up
PU means an isocyanate-cured two-pack coating. The film is hard, chemically cross-linked and continuous, which is why it can be sprayed over a routed profile and read as one piece of moulded material. Getting there takes more passes than clients imagine.
| Stage | Coats | What it does | Sanding between |
|---|---|---|---|
| Substrate preparation | — | HDHMR or MDF routed, edges sealed, dust blown off | 180 grit |
| PU putty | 1 – 2 | Fills router marks and board texture; the flatness of the final panel is decided here | 240 grit, thorough |
| PU sealer | 2 | Builds film and stops the colour coat sinking into the board | 320 grit |
| Colour coat | 2 | Tinted to the approved shade; sprayed wet-on-wet | 400 grit, light |
| Clear topcoat | 1 – 2 | Carries the sheen and the abrasion resistance | Buff only |
Total dry film thickness should land between 90 and 120 microns. Under 70 microns the board texture telegraphs through within a year.
2026 rates, and what moves them
| Specification | Rate (₹/sq ft of elevation) | When it is the right choice |
|---|---|---|
| Site-sprayed PU, matte, on MDF | ₹640 – 780 | Budget bespoke colour on low-touch panelling |
| Booth-sprayed PU, matte, on HDHMR | ₹820 – 980 | Our default for kitchen and wardrobe shutters |
| Booth-sprayed PU, high gloss, buffed | ₹950 – 1,150 | Show kitchens; requires three buffing passes |
| PU over routed shaker or fluted profile | ₹900 – 1,250 | Profiled work — the profile adds surface area and masking time |
| Matt PU over natural veneer | ₹150 – 220 over the veneer rate | Clear system only; no colour coat |
| Touch-up and re-coat of existing PU | ₹180 – 320 | Year 8–12 refresh, done in situ |
A 10 ft × 8 ft wardrobe elevation in booth-sprayed matte PU is roughly ₹66,000–78,000 of finish alone, before carcass and hardware.
Sheen: the specification clients forget to give
Sheen is measured at 60 degrees on a gloss meter and it is the difference between a panel that looks like furniture and one that looks like a car door. Decide it on a sample, in your own light, at the time of day you use the room.
- Dead matt, 5–10 sheen. Beautiful, shows every fingerprint and every wipe mark. We use it on bedroom panelling, rarely on kitchens.
- Matt, 15–30. The sensible default. Hides marks, cleans easily, photographs well.
- Satin, 35–50. Slight lift for darker colours that would otherwise look flat and chalky.
- High gloss, 85+. Requires buffing and a dust-free booth. Any imperfection in the putty stage is magnified, so it costs more in preparation than in paint.
Mumbai conditions: the two things that ruin PU
PU cures by chemical reaction, not by evaporation, so it is less humidity-sensitive than NC lacquer. What it is sensitive to is airborne dust and surface moisture at the moment of spraying.
- Dust. Spraying in an occupied flat during civil works guarantees a nibbed finish. If site spraying is unavoidable, the room is sealed with polythene, the floor is wetted, and no other trade works that day. We prefer to spray in the workshop and bring finished panels in.
- Monsoon moisture. Board absorbs moisture in a humid room and the sealer then blisters. We check board moisture content before spraying and will push the schedule rather than spray a damp panel.
- Salt. Near the sea, deposits build on a matte PU surface and dull it. The answer is dry dusting weekly, not a harder coating.
One genuine advantage in this climate: a damaged PU panel is sanded locally, re-sprayed and blended, with no dismantling. Laminate, acrylic and membrane all have to be taken off and replaced.
Care, life and the BOQ clauses that matter
- Clean with a soft damp cloth. No alcohol, no thinner, no ammonia glass cleaner — all three soften a fresh film in the first 30 days.
- Allow 7 days before hanging heavy items against the surface; full cure is 14–21 days even though the panel feels hard in 24 hours.
- Expect 12–18 years of service with one in-situ re-coat around year nine.
- BOQ: “Two-pack PU system on 18 mm HDHMR — PU putty, two coats PU sealer, two coats tinted PU, one clear topcoat; minimum DFT 90 microns; sheen 20 ± 5 at 60°; sprayed off site in controlled conditions.”
- BOQ: “Approved sample panel 300 × 300 mm to be signed by client for both shade and sheen before bulk spraying. Site touch-up of edges included in rate.”
Specification summary
| Property | Specification |
|---|---|
| System | Two-pack polyurethane, isocyanate cured |
| Substrate | 18 mm HDHMR preferred; MDF acceptable for dry, low-touch work |
| Coats | Putty + 2 sealer + 2 colour + 1 clear |
| Dry film thickness | 90 – 120 microns |
| Sheen | Stated at 60°; 20 ± 5 for general work |
| Rate | ₹640 – 1,150 per sq ft of elevation, ex-GST |
| Repairability | Full — sand, re-spray, blend in situ |
| Avoid | Site spraying in an active dusty flat; pure white in strong daylight |
Frequently asked questions
Is PU better than acrylic?+
They solve different problems. Acrylic is a bonded sheet with a flawless flat face and huge scratch resistance, but it only comes in flat panels and set colours. PU is sprayed, so it takes any colour, any sheen and any profile, and it can be repaired. On flat slab shutters acrylic usually wins; on profiled or curved work PU is the only real option. Our acrylic versus PU page works through it.
Does white PU turn yellow?+
Slightly, yes. Aliphatic topcoats resist it far better than aromatic ones, but over five to seven years a pure brilliant white will warm perceptibly, most visibly where sunlight falls. If you want white joinery to hold for a decade, pick an off-white with a grey or warm base rather than the purest white on the fan deck.
Can PU be sprayed inside my flat while I am living there?+
It can, but we advise against it. The overspray travels, the solvent smell lasts three to four days, and dust nibs in the film are permanent. We spray in the workshop and install finished panels, which reduces your disruption to a day of fitting.
How do I know I actually got seven coats?+
Ask for a wet-film thickness reading during application and a dry-film reading on a test coupon at the end, and keep the signed sample panel. A shortfall shows up as board texture visible through the film in raking light within twelve months — by which time the argument is expensive.
What does re-coating existing PU cost?+
In Mumbai, ₹180–320 per sq ft of elevation for a scuff, one colour coat and a fresh clear, done in place over two to three days per room. It is the cheapest way to make a decade-old kitchen look new, and no other opaque finish on this site offers it.