Buyers often ask us for a price per square metre of duct. We do not publish one, because the price follows from what is in the bill of quantities (BOQ): the duct type, the thickness of the steel, the fittings, the insulation and accessories, and who installs it. This guide explains each factor, so you can read a quotation and compare like with like.
GI or PI duct: the first cost decision
The first decision is the duct itself. GI duct is fabricated from galvanized steel with a minimum zinc coating of 275 g/m² (BS EN 10346), in rectangular, circular and oval profiles. Pre-insulated (PI) duct is made from panels with a rigid foam core and aluminium foil faces, so the insulation is part of the duct.
| Cost driver | GI duct | PI duct |
|---|---|---|
| Material | Sheet thickness and the amount of steel | The core (phenolic or PIR) and the panel thickness |
| Insulation | A separate material and a separate labour step on site | Arrives insulated |
| Installation | Installed first, insulated afterwards | Assembled from factory-cut panels |
| Weight and supports | Heavier with its insulation; hangers and supports must suit the weight | Light, which matters on light ceilings |
Our GI vs PI duct guide compares the two in detail, including where each one fits. If you are unsure, send one BOQ and we will quote both options: GI duct with the insulation you specify, and phenolic or PIR duct.
Sheet gauge, duct size and pressure class
For GI duct, the amount of steel depends on the sheet thickness, or gauge. Our GI duct datasheet covers sheet from 0.4 mm up to 3 mm (for rectangular duct, the SMACNA tables give 0.60–1.5 mm), and the thickness is not a free choice: it follows the duct size and the pressure class.
We fabricate rectangular GI duct to the SMACNA gauge and joint tables for the 500 Pa, 750 Pa and 1000 Pa pressure classes. A larger duct or a higher pressure class can call for a heavier gauge, so the same route can need more steel in a higher class. Our guide to SMACNA pressure classes and duct gauge explains how the tables work.
Fittings, insulation and accessories
A duct order is more than straight duct. These lines in the BOQ also decide the total:
Fittings vs straight runs
Elbows, branch connections and other fittings are listed apart from straight duct, and the mix of the two changes the price of the order.
Insulation for GI duct
GI duct is not insulated when it is made. Insulation, such as NBR rubber foam sheet, is a separate material with its own site labour.
Flanges and joints
TDC/TDF flanges, corner pieces and S-drive or standing drive cleats join the duct sections.
Sealant and tape
Acrylic duct sealant bonds and seals joints, and aluminium foil tape seals joints and seams on foil-faced insulation.
PI duct has its own accessories, such as the aluminium F, U and chair profiles for 20 mm panels. You will find all of them in our accessories range.
Supply, installation and delivery
We offer both supply only and supply and installation, so state on the BOQ which one you need. Delivery terms are the same for every customer:
- Delivery is free within Doha for duct orders above 100 m².
- Delivery is free within Doha for accessory orders above QAR 6,000.
- Delivery to other areas of Qatar is available; ask for the cost with your quote.
- There is no minimum order: we supply any quantity, from a single fitting to a full project.
- Standard GI and PI duct orders are usually ready within 2 working days of order confirmation; large or special orders are scheduled with you when we quote.
How to get an accurate quotation
Send your BOQ or product list
Use the quote form, or email the BOQ, drawings or specification to hvac@tawreed.ltd or send them on WhatsApp to +974 7097 0111, quoting your project name.
Give sizes, quantities and the pressure class
List each product type with its quantity and unit (m, pcs, m² or sets), dimensions in mm and notes such as sheet thickness or fire rating.
State the scope and delivery
Say whether you need supply only or supply and installation, the delivery location and the required delivery date.
Receive a formal quotation
Our technical team replies with a formal quotation within 4 business hours.