In-House Duct Manufacturing vs Outsourced — Why It Matters on Dubai Fit-Outs

A retail fit-out in Mall of the Emirates ran on a 6-week construction window. The duct fabrication was outsourced to a workshop in Al Quoz. The shop drawing was issued on day 14. Standard galvanised rectangular, nothing exotic. The first ducts arrived on day 26 — twelve working days later. The contractor lost a full week of schedule on a single line item, the schedule slid into mall management’s no-extend zone, and the opening was pushed three weeks.

This is not unusual. On Dubai fit-outs, ductwork is one of the longest-lead MEP elements when it is outsourced, and one of the most schedule-critical when it is not on site. This article is for fit-out project managers, commercial property managers and developers running fit-outs across Business Bay, DIFC, the malls, the free zones — the people whose schedules live or die by how quickly the ducts arrive. It compares in-house versus outsourced duct manufacturing on three axes that actually matter: lead time, margin, and quality control.

What “in-house duct manufacturing” actually means

Some fit-out contractors say “in-house” when what they mean is “we have a preferred subcontractor”. A true in-house workshop has:

• A facility you can walk into during a site visit.
• Owned machinery — typically a coil line, a plasma cutter or beading machine, a TDC/TDF flange former, a press brake, a Pittsburgh seamer.
• Direct material stock — galvanised sheet on the floor in standard gauges, not ordered per job.
• A foreman who reports to the fit-out company, not a separate vendor.
• A schedule controlled by the same project manager running the construction.

When you ask a fit-out contractor “are you in-house on ducts?” — those five points are the test. If the answer is “we have a great relationship with a fabricator”, that is outsourced.

The lead-time saving — what you actually get back

Standard outsourced duct fabrication in Dubai, for typical rectangular galvanised work, runs 7 to 14 working days from drawing approval. In peak fit-out season — which in Dubai means anytime there is mall pressure for opening dates or anytime free-zone fit-outs surge — it stretches to 10 to 18 days.

A capable in-house workshop turns the same scope in 1 to 3 working days. On a 6-week fit-out, that recovers a full week of schedule. On a 12-week fit-out it recovers two weeks. The maths is simple — fabrication moves from the critical path to a parallel workstream.

Why the gap exists:

• Queue position. An outsourced fabricator is running jobs for 30+ contractors. Your job sits in the queue. An in-house workshop is running jobs for one contractor — the one paying the rent.
• Drawing-to-cutting handoff. Outsourced, the shop drawing is reviewed, BOQ’d, the order is approved, the material is allocated, the job is scheduled. In-house, the shop drawing goes to the foreman the same day it is signed off.
• Delivery scheduling. Outsourced fabrication has to schedule deliveries between other clients. In-house deliveries are scheduled by your site engineer.
• Rework cycles. Site changes always come up — a beam in the wrong place, a service crossing, an ELV tray clash. With an in-house workshop, a piece comes back, gets modified, returns the same day. Outsourced, it is another 2–5 days in the queue.

For commercial property managers running fit-out programmes — multiple units, multiple openings — this matters compoundingly. Across ten fit-outs, in-house duct manufacturing saves 50 to 100 working days of schedule slack.

The margin saving — where it actually shows up

Outsourced duct fabrication carries a fabricator’s margin on top of the material and labour cost. That margin is real — typically 18–28% on standard galvanised work, more on bespoke. When the duct work passes through a main contractor on the way to you, there is another mark-up.

An in-house workshop is paid for once — the contractor’s own labour and material at the contractor’s own cost base. On a typical office fit-out where ductwork is 8–12% of the BOQ, eliminating the fabricator margin is worth 1.5 to 3% of the total BOQ. On a AED 1.5m office fit-out that is AED 22,000 to 45,000 of avoidable cost — without changing scope, finish, or specification.

The honest caveat: not every in-house contractor passes that saving to you. Some keep it as additional margin. Ask in the negotiation. The fabricated AED per sqm rate is benchmarkable — if the in-house workshop’s rate matches the outsourced rate, you are paying for the workshop’s overhead, not benefiting from it.

Quality control — the bit no one talks about until it goes wrong

Ductwork quality issues do not always show on day one. They show six months in, when the building has been balanced and the office is occupied. Then you start to see:

• Excess noise from joints that were not properly sealed.
• Pressure drops higher than design — fans running harder, DEWA bill creeping.
• Air leakage into the ceiling void rather than into the room.
• Vibration transmission from the AHU because the flex connector was undersized.
• Insulation pulling away from the duct because the adhesive class was wrong for the application.

These are not glamorous problems but they are real and they are expensive to fix retroactively. They come from three places: wrong gauge for the duct size, wrong sealing method for the joint type, and wrong insulation class for the route.

Gauge selection

SMACNA — the Sheet Metal and Air Conditioning Contractors National Association — publishes the standard reference for rectangular duct construction. The gauge of galvanised steel sheet you use depends on the duct’s longest side and the static pressure class. A 600mm side at low pressure can use 0.7mm gauge. A 1500mm side at the same pressure class needs 1.0mm. Get it wrong and the duct deforms, oil-cans on starting torque, and leaks at the seams.

An outsourced fabricator working to a generic spec may default to the lighter gauge to save cost. An in-house workshop where the fit-out company also runs the BMS commissioning has a direct interest in getting it right — they are the ones who have to fix the noise complaint six months later.

Joint sealing

Joints between duct sections are made in four ways depending on size and pressure class:

• TDC (Transverse Duct Connector) — bolted, gasketed flange. The current Dubai standard for medium and large rectangular duct. Tight seal, low leakage, faster install.
• TDF (Transverse Duct Flange) — similar concept, slightly different geometry.
• Slip-and-drive — older method, still used for smaller ducts. Cheaper, more leakage if not sealed properly.
• Pittsburgh seam — longitudinal seam, not transverse. Inside the duct itself.

Sealant matters. Mastic-based duct sealant rated to the pressure class, applied properly, makes a TDC joint effectively airtight. The same sealant applied wet or to a dusty flange is half-effective. Quality control is the difference between a properly leak-tested duct and a duct that bleeds 15% of its conditioned air into the ceiling void.

Insulation class

Insulation choice depends on the duct’s route:

• Fibreglass blanket — for internal runs within conditioned space.
• Armaflex or Aeroflex elastomeric closed-cell — for runs through unconditioned spaces. Vapour barrier built in.
• Fire-rated insulation — where DCD or building regulations require, typically near fire dampers, plant-room penetrations, and shaft routes.
• Foil-faced — where vapour barrier is critical, condensation risk exists, or as required for cleanability.

The wrong class fails. Fibreglass in an unconditioned ceiling void with a high vapour load sweats — condensation forms inside the insulation, the foil-faced layer pulls away, mould appears on the duct exterior. Fixing this retroactively means pulling ceilings, stripping insulation, re-wrapping with the correct class. It is one of the most expensive HVAC retrofit jobs we see, and almost always tracks back to a fabricator who specified one class for the whole job rather than reading the route.

What good in-house duct fabrication looks like

• Standard 0.7mm or 1.0mm galvanised steel on the workshop floor in stock — not ordered per job.
• SMACNA-aligned rectangular duct construction. Round duct where the route or pressure class demands it.
• TDC flange forming integrated into the production line — not a separate sub-operation.
• Pittsburgh-seamed longitudinal on the duct itself.
• Fire dampers coordinated with the DCD-approved spec, installed under the workshop drawing.
• Insulation applied in-workshop where the route is known and pre-fabricated, on-site where last-mile flexibility is needed.
• Pressure-class confirmation on the shop drawing — Class 1, 2 or 3 specified, gauges sized accordingly.

What to ask any fit-out contractor before signing

• Are you actually in-house, or do you use a preferred fabricator? The five-point test above.
• What is your standard lead time from approved shop drawing to first delivery? 1–3 days is in-house. 7+ days is outsourced.
• What SMACNA class are you fabricating to? If they cannot tell you, walk away.
• What gauges are you using for which duct sizes? Should be on the shop drawing.
• What joint type and sealant? TDC, TDF, slip-and-drive — for which sizes, with which sealant.
• What insulation class for which routes? Should be specified on the drawing per route, not a single class for the whole job.
• Are fire dampers in scope, and is DCD coordination handled? If yes, who lodges what.
• Can the rate be benchmarked against outsourced fabrication? AED per sqm rate is the right comparison.
• What is the workmanship warranty? Six months on workmanship is the floor. Material warranties from the steel and insulation manufacturer pass through directly.

When outsourced is fine

To be fair to outsourced fabrication: there are scopes where it is the right answer. Specialist round-duct work with custom fittings, very large industrial ducts beyond standard workshop capacity, spiral duct in exotic gauges, fire-rated steel duct for plant rooms. Most workshops, in-house or not, sub these specialty items out. The point is not “in-house always wins” — it is “in-house wins on the 80% of standard rectangular fit-out work that drives most schedules”.

Cost ranges to benchmark against

For Dubai fit-out work in 2024–2026, rough AED per sqm rates including fabrication, supply and install:

• Standard rectangular duct, fabricated and installed: AED 250–450 per sqm.
• Spiral round duct, fabricated and installed: AED 350–600 per sqm.
• Fire-rated duct, fabricated and installed: AED 600–1,200 per sqm.
• Insulation — fibreglass: AED 50–90 per sqm. Elastomeric Armaflex/Aeroflex: AED 90–160 per sqm. Fire-rated: AED 150–250 per sqm.

These are install-on-site rates. Pure workshop fabrication without installation runs lower. Get a line-item BOQ — fabrication and installation broken out — so you can compare apples with apples.

If you are running a Dubai fit-out programme

Send us your shop drawing — or your architectural plus mechanical floor plan if the drawings are not yet at shop stage — and we will quote duct fabrication on AED per sqm with a clear lead time. Our workshop runs standard galvanised in 1–3 working days from approved drawing. SMACNA-aligned, TDC-flanged where the size and class demand it, insulation specified per route. Fabricated and installed by the same in-house MEP team, so the joint sealing, the hangers, the balancing, the commissioning are all under one warranty.

WhatsApp +971 52 423 0419 or send drawings by email. We will come back with an AED per sqm rate and a fabrication lead time inside two working days — and on a real fit-out schedule, that is the answer that actually matters.