What Architects Should Ask Before Specifying a Polycarbonate System

Polycarbonate is one of the most versatile materials in the building envelope toolkit. It offers daylight, thermal performance, impact resistance, low weight, and form flexibility that glass simply cannot match at scale. But it is also a category where specification quality varies dramatically — and where a poorly specified product creates a building that yellows, leaks, or rattles within a decade.

This post is a working checklist for architects and building envelope consultants. Use it during pre-specification briefings, product evaluations, and tender reviews.

1. What is the UV protection specification — exactly?

This is the single most important question to ask. All polycarbonate exposed to sunlight degrades over time without UV protection. The industry standard method is co-extrusion: a UV-absorbing layer is molecularly bonded to the polycarbonate during manufacturing.

What to specify:

Top (sun-exposed) layer: Minimum 45–50 microns of co-extruded UV protection
Bottom (interior) layer: Minimum 15 microns co-extruded UV protection

Ask whether the UV protection is co-extruded or surface-applied. Co-extrusion is permanent — it cannot peel, flake, or be washed away. Surface coatings are not equivalent. A supplier who cannot confirm co-extrusion thickness in writing should be treated with caution.

2. What are the tested panel dimensions — and why does width matter?

Panel width affects structural behaviour more than most buyers realise. Wider panels flex more under wind load, are more prone to oil canning (visible waviness under wind pressure), and create more visible vibration at intermediate purlin spans.

Industry-standard best practice for standing seam polycarbonate systems is 900mm panel width. This width delivers:

Optimal wind uplift resistance
Reduced oil canning tendency
Better visual flatness over the span
Controlled thermal expansion behaviour

Specifications that allow "minimum 900mm" or "any width" effectively open the door to wider, cheaper panels that underperform. A well-written specification should set width as a performance variable, not an afterthought.

Also check: standing seam height. A minimum 15–20mm vertical standing seam on both sides of the panel is required for proper connector grip and uplift resistance. Welded or glued standing seams are not acceptable substitutes for extruded ones.

3. What third-party test certificates exist, and are they current?

A serious manufacturer provides third-party test certificates from NABL-accredited laboratories. The minimum test set for a standing seam polycarbonate system should cover:

Test	Standard
Yellowness Index (UV ageing)	ASTM E-313 / ASTM D1925 after 500 hrs ASTM G-155
UV Exposure (accelerated weathering)	ASTM G-155 (Xenon arc)
Dart Drop Impact	IS 14443-97 (post UV exposure)
Flammability	UL-94 (minimum V2 classification)
Thermal transmittance (U-value)	EN ISO 10077-2
Fire reaction (for premium systems)	EN 13501-1 (B-S1-D0)

Test certificates should be dated within the last 5–8 years and should cover panels that have actually been installed in comparable Indian climate conditions for the stated duration. Ask for PO copies showing a minimum of 3,000 sqm of comparable installations in India.

4. What is the fixing system, and what is its pull-out resistance?

The fixing system determines wind uplift performance. For standing seam systems, the correct fixing method is an I-shape notching aluminium cleat — a pre-built cleat that grips the standing seam from at least one side using a locking mechanism.

Minimum pull-out load: 7,000 N (7 kN) per ISO 6892.

Systems that rely only on fasteners through the panel face are not standing seam systems. Fastener-through-face fixing creates leak points and limits uplift resistance.

Also check: Does the connector system use a double-tooth interlocking grip-lock mechanism? Single-lock connectors are weaker and more prone to uplift failure in high-wind conditions.

5. How is watertightness achieved at panel ends?

Leaks in polycarbonate roofing almost always originate at the ends, not the panel joints. End treatment must include:

Aluminium U-profile / glazing bar on all exposed panel ends
Aluminium tape sealing the open cellular structure at the ends
Polycarbonate end caps to prevent dust ingress into the cell structure
Minimum roof slope of 5–7° for adequate drainage

Any system that relies on sealant alone for end closure is a maintenance liability. Aluminium closure profiles with tape are the correct specification.

6. What is the manufacturer's India experience and warranty terms?

This is a due diligence question, not a brand question. The relevant checks:

Own manufacturing plant in India (not just an importer or trading company)
Minimum 8–10 years of manufacturing experience for the specific system type
Projects installed at least 5–8 years ago still performing adequately (request references)
10-year warranty against manufacturing defects, in writing

The Indian climate — particularly UV intensity, thermal cycling, and monsoon loading — is different from European test environments. A product manufactured and installed for 8+ years in Indian conditions has demonstrably survived local stresses. An imported or newly manufactured product has not.

Summary Specification Checklist

□ Co-extruded UV protection: 45–50 microns top / min. 15 microns bottom
□ Panel width: 900mm (not more, not less — stated as performance requirement)
□ Standing seam: extruded, min. 15–20mm height, both sides
□ Test certs: ASTM E-313, G-155, IS 14443-97, UL-94, EN ISO 10077-2
□ Certs from NABL-approved labs, within last 5–8 years
□ Fix method: I-shape notching AL cleat, double-tooth grip-lock
□ Pull-out load ≥7,000N (ISO 6892)
□ End closure: AL U-profile + AL tape + PC end cap
□ Minimum slope: 5°–7°
□ Manufacturer: own plant, 8–10+ years India experience
□ Warranty: 10 years against manufacturing defects
□ Reference projects: 3,000+ sqm, installed 5–8 years ago

Coxwell supplies standing seam polycarbonate systems manufactured at our facility in Alwar, Rajasthan. All systems are backed by third-party NABL-certified test reports. Request our full technical datasheet or specification assistance for your next project.