Estimation & Costing for Aluminium & Glass Façade Works

**Why façade estimation matters**

Façade costs can make or break a project budget, especially when dealing with aluminium and glass systems. Underestimating the amount of extrusions, brackets, or glazing can lead to cost overruns, delays, and disputes with contractors.

**Who this helps**

This guide is for quantity surveyors, estimators, project managers, and site engineers working on buildings with curtain wall or structural glazing. It is particularly useful for those new to aluminium and glass works who need a methodical approach to take-off, costing, and quality control.

## Foundations: components of an aluminium & glass façade

A building façade consists of framing members (vertical mullions and horizontal transoms), glass panels, anchor brackets, brackets and bolts, sealants, insulation, and sometimes aluminium composite panels or louvers. Each component has specific measurement rules. For extrusions, you measure running metres; for glass, you measure area; for fixings and brackets, numbers.

## Step-by-step quantity take-off

1. Review architectural elevations and schedules. Identify façade zones (stick system vs unitised system).

2. Calculate the overall façade area (height × width) for each elevation.

3. Divide into bays based on grid spacing. Determine mullion lengths and transom lengths for each bay; multiply by number of bays.

4. For glass panels, calculate clear opening width and height, then multiply by number of panels. Add allowances for edge cover and cutting waste.

5. List ancillary items: pressure plates, caps, gaskets, brackets, screws, sealants. Quantify based on per metre of frame or per joint.

6. Assess special elements: corner profiles, spandrel panels, louvers, doors, windows. Quantify individually.

7. Apply thickness and performance specification: glazing thickness (6mm, 12mm etc.), coating type (clear, tinted, low-E). This influences weight and cost.

## BOQ & rate analysis

Here is an example of a simplified Bill of Quantities for a mid‑rise façade system:

| Item | Unit | Qty | Rate (₹) | Amount (₹) |

|---|---|---|---|---|

| Aluminium mullions 75mm x 50mm | m | 1,200 | 600 | 720,000 |

| Aluminium transoms 50mm x 50mm | m | 900 | 550 | 495,000 |

| 6mm clear tempered glass panels | sqm | 650 | 1,100 | 715,000 |

| Brackets & anchors | pc | 1,000 | 120 | 120,000 |

| Sealant (silicone) | ltr | 200 | 450 | 90,000 |

| Labour and installation | lumpsum | 1 | 400,000 | 400,000 |

## Key formulas

- Mullion length = storey height + splice allowance

- Glass panel area = panel height × panel width

- Section weight (kg) = sectional area (mm²) × length (m) × density (kg/mm³)

## India vs GCC: site examples

In India, extrusions often use aluminium alloy AA6063 T6, with typical mullion spacing of 1.2–1.5 m. Glass is often 6+12A+6 mm double‑glazed. Sealants must comply with IS 11056. In GCC countries like UAE or Qatar, extrusions may be heavier due to higher wind loads (up to 4 kPa), using unitised systems. Glazing may be 8+12A+6 mm or incorporate low‑e coatings to reduce solar gain. Fixings should be stainless steel to resist corrosion from saline environments.

## Common mistakes & how to avoid them

- Ignoring edge cover when measuring glass leads to undersized panels; always add 10‑20 mm on each edge.

- Underestimating waste factor for extrusions; include at least 5–7% for cutting and splicing.

- Assuming identical panel sizes across elevations; check each bay individually.

- Overlooking accessories like EPDM gaskets; account for them per metre of framing.

- Failing to include scaffolding or access equipment; incorporate into installation cost.

## Mini QA/QC checklist

1. Verify aluminium alloy grade and temper against specifications.

2. Check extrusion dimensions and tolerances using callipers.

3. Ensure glass panels are tempered or laminated as required; verify thickness and coatings.

4. Inspect factory fabrication: drilling of holes, slotting, corner keys.

5. Check the quality of powder coating or anodizing on extrusions.

6. Confirm bracket and anchor bolt sizes and embedment depth.

7. Examine sealant batch numbers and expiry dates.

8. Conduct water penetration test after installation.

9. Ensure proper thermal break installation to prevent condensation.

10. Review installation torque for fasteners.

## Frequently asked questions

**Q: How is the weight of aluminium sections estimated?**

A: Determine the cross‑sectional area in mm² (from the supplier catalogue). Multiply by length in metres and the density of aluminium (approx. 0.0027 kg/mm³).

**Q: What is the difference between stick and unitised systems?**

A: Stick systems are assembled piece by piece on site, requiring more labour. Unitised systems are pre‑assembled panels delivered to site, reducing installation time but requiring precise fabrication.

**Q: How do you account for wind load in cost?**

A: Higher wind loads necessitate larger section sizes and thicker glass, which increases material quantities and cost. Use structural calculations to determine section sizes.

**Q: Why include waste in take‑off?**

A: Extrusions and glass come in standard lengths; cutting to exact sizes results in off‑cuts. Including a waste factor ensures you procure enough material.

**Q: What are typical payment stages for façade works?**

A: Typically, payment is tied to procurement of materials (30–40%), fabrication completion (30%), installation milestones (20–30%), and final testing and handover (10%).

## Call to Action

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