Buying Guide

What Is a Veranda Actually Made Of?

A proper look at the aluminium, glass, polycarbonate, rubber, and steel that goes into a quality veranda — and why each material is there

Posted 13 April 2026

Most veranda brochures tell you a structure is “made from aluminium” and leave it at that. It's true, technically. But it's a bit like describing a Mercedes as “made from metal.” The interesting part is which metal, in what form, processed how — and whether the manufacturer has cut corners on any of it.

This guide goes into the detail that usually gets left out. Not into materials science territory, but enough that you'll understand what you're actually buying, why certain specifications matter, and what separates a veranda that lasts 60 years from one that doesn't.

If you just want a quick overview before diving in, the summary below shows what every model is made of at a glance.

The Frame: 6063-T6 Aluminium

The posts, beams, gutters, and wall plates that make up a veranda frame are all extruded from aluminium alloy 6063 — also known in the industry as the “architectural alloy.” It's the same family of alloys used in aircraft fuselage frames, automotive structural components, and aerospace fittings — applications where engineers need a material that's genuinely strong, corrosion-resistant, and reliably consistent over a long service life. When you're told your veranda is made from T6 structural aluminium, that's not marketing language — it's a materials specification with a real engineering pedigree.

The “6063” part refers to the alloy's composition: it's primarily aluminium, with around 0.5–0.9% magnesium and 0.2–0.6% silicon added in. Those two elements — magnesium and silicon — are what allow the aluminium to be heat-treated into something genuinely structural. Without them, you'd have soft, weak raw aluminium. With them, and with the right heat treatment, you get something strong enough to span several metres between posts under wind and snow loads while remaining lightweight enough to handle without heavy machinery.

What the T6 means

The “T6” is the temper designation — it describes the heat treatment the aluminium has received. T6 is the most common and most important temper for structural aluminium, and understanding it takes about thirty seconds.

Fresh off the extrusion press, 6063 aluminium is relatively weak. To harden it, manufacturers heat it to around 520°C — dissolving the magnesium and silicon into the aluminium at the atomic level — then rapidly cool it (this is called quenching), and finally reheat it gently to around 170°C for a few hours. This final step, called artificial ageing, causes the magnesium and silicon to precipitate out of solution as incredibly fine particles distributed throughout the metal. Those particles are what give T6 its strength — they act as barriers to the tiny movements within the crystal structure that cause metal to deform. The result is aluminium that's roughly 4 to 5 times stronger than the same alloy without the treatment.

T6-tempered aluminium is the specification of choice for aircraft frames, automotive structural parts, and high-performance engineering components — anywhere that lightweight material needs to hold its shape under sustained load without corroding. The same process that keeps an aircraft fuselage rigid and reliable for decades does the same job in your veranda frame.

Why aluminium rather than steel or timber

Steel is stronger, but it's also three times heavier and requires ongoing protection against rust. Timber looks beautiful but needs regular repainting or staining, swells and contracts with moisture, and is vulnerable to rot. Aluminium's great advantage is that it forms its own protective oxide layer when exposed to air — it doesn't corrode in the way steel does. For an outdoor structure that's designed to need minimal maintenance for decades, it's the obvious choice.

How the profiles are made: extrusion

The frame profiles aren't machined from solid bar — they're extruded. A heated aluminium billet is pressed under enormous hydraulic pressure through a shaped steel die, emerging as a continuous length of precisely shaped profile. Think toothpaste being squeezed through a nozzle, but with enormous force and temperatures above 450°C.

This matters because extrusion is the only process that allows the complex internal shapes that make veranda frames work. The integral gutter channel, the hidden fixing slots, the hollow post sections that let cables run through invisibly — none of these could be drilled or machined economically. Extrusion forms them all in a single pass. The quality of a manufacturer's die engineering — and the tolerances they work to — is what separates a veranda that goes together cleanly from one that requires shimming and adjustment on site.

The Finish: Powder Coating (and What Marine Grade Actually Means)

Raw extruded aluminium is dull silver. The colour and long-term protection come from polyester powder coating — a process that's genuinely different from wet paint and considerably better for outdoor use.

The powder — a dry blend of polyester resin, pigments, and hardener — is given an electrostatic charge and sprayed onto the pre-treated aluminium. The charge makes the powder particles cling uniformly to every surface, including recesses and edges. The coated profile then passes through a curing oven at around 180–200°C, where the powder flows, levels, and undergoes an irreversible chemical reaction that transforms it into a hard, dense film. Once cured, it cannot be melted back. It's harder, more flexible under impact, and more scratch-resistant than wet paint of equivalent thickness.

The most important step, however, is what happens before the powder goes on. The aluminium surface must be chemically etched to remove extrusion contaminants and create a proper key for the coating to bond to. Without it, the powder coating would eventually lift — not because the powder failed, but because the surface beneath it wasn't properly prepared.

QUALICOAT Seaside — what “marine grade” actually means

There's a specific standard for this pre-treatment on architectural aluminium: the QUALICOAT Seaside specification, introduced in 2008 for structures in coastal and exposed environments. Standard powder coating requires the aluminium surface to be etched to a depth of 1 gram per square metre. Seaside class requires 2 g/m² — twice as deep. That deeper etch removes more contaminants, creates a more robust surface for the coating to grip, and gives significantly better resistance to the type of creeping corrosion that salt air causes.

QUALICOAT licences are audited by an independent body twice a year, unannounced. When we say our British-made models — the Haven, Pavilion, and Vista — come with marine grade coating as standard, we mean they're coated to this specification. It's one of the reasons those models carry a 60-year life expectancy. It's included in the price.

The Roof: Toughened Glass (6mm)

Glass is the premium roof choice — it looks spectacular, is acoustically superior to polycarbonate in rain, and doesn't yellow or discolour. The glass used on our British-made glass-roofed models (Haven, Pavilion, Vista) is 6mm toughened safety glass.

Where glass starts: the float process

All architectural glass begins as float glass. Molten glass — primarily silica sand, soda ash, and limestone melted together at around 1,500°C — is poured onto a bath of liquid tin. The glass floats on the tin surface, spreads out under gravity and surface tension, and forms a sheet of perfect flatness and uniform thickness with fire-polished surfaces on both sides. It then travels through a long controlled-cooling tunnel (called an annealing lehr) to relieve internal stresses before being cut to size. This process, developed in the 1950s, is how virtually all flat glass in the world is made today.

How toughening works

Float glass is cut to its final dimensions — any edge work, drilling, or notching must happen before toughening, because the glass cannot be cut or altered afterwards. The panel is then washed, loaded into a tempering furnace, and heated to approximately 620°C — just above the temperature at which the outer surface begins to soften slightly.

The glass then passes immediately into a quenching station where high-pressure air jets blast both surfaces simultaneously. The surfaces cool and harden almost instantly. The interior is still hot and contracting. As the core eventually cools, it tries to shrink — but it's locked between the already-rigid surfaces. This sets up a permanent state of compressive stress at the surfaces and tensile stress in the interior.

It's this stress that gives toughened glass its properties. The surface compression is what you have to overcome before the glass can fail — making it roughly 4 to 5 times stronger than the same float glass untreated. The same residual stress also explains the breakage pattern: when toughened glass does break, the stored energy releases instantly, causing the panel to disintegrate into small, blunt granules rather than large, sharp shards. That's the safety feature.

The same type of glass is used in car side windows, shower screens, glass balustrades, and glass table tops — anywhere that both strength and safe breakage behaviour are needed.

The self-cleaning upgrade

Available on glass-roofed models, self-cleaning glass has a nano-scale titanium dioxide (TiO₂) coating fused into the outer surface. TiO₂ is photocatalytic — UV from daylight triggers a reaction that breaks down organic grime (pollen, algae, general dirt) into compounds that wash away easily. It's also hydrophilic when UV-activated, meaning rainwater spreads as a thin sheet rather than beading, carrying loosened particles cleanly off the surface. In the UK climate — moderate UV plus reasonable rainfall — it meaningfully reduces how often you need to clean your roof.

The Roof: Laminated Safety Glass (44.2)

The Dutch-made Sanctuary model uses a different type of glass roofing entirely: 44.2 laminated safety glass. The “44.2” is a construction code — two 4mm glass panes with two layers of PVB film between them.

What PVB is and where it came from

PVB stands for polyvinyl butyral — a tough, transparent plastic film. It was developed in the 1930s for car windscreens: the goal was to stop windscreens shattering into razor-edged shards in crashes. PVB bonds strongly to glass and has high tear resistance — so fractures don't propagate through it. The same technology that protects car occupants in accidents is what makes laminated glass safe for overhead use in verandas.

The two glass panes and the PVB film are bonded together under heat and pressure in an industrial autoclave. Once fused, the assembly is a single inseparable unit. The glass panes themselves are non-toughened (annealed) — deliberately so. Toughened glass breaks into granules that can detach from the film. Annealed glass fractures into larger pieces that the film holds together more effectively as a continuous sheet.

Why it matters for overhead glazing

When laminated glass breaks — from impact, thermal stress, or a structural fault — the PVB film acts as a carrier. The fragments stick to it. The panel cracks but stays in position rather than falling. For a glass panel directly above people, this is a meaningful safety advantage over toughened glass, which shatters completely on failure even if the fragments are blunt.

PVB also filters up to 99% of UV radiation, protecting furniture and flooring beneath the roof from fading — a useful bonus for a space you're likely to furnish properly. And it adds acoustic damping: rain on laminated glass is noticeably quieter than rain on toughened glass of the same thickness, because the viscoelastic film absorbs sound energy.

Why the Sanctuary needs a steel-reinforced gutter for glass

Laminated glass is heavier than toughened glass of similar thickness. A full glass roof on a wide, deep veranda creates significant loading on the front beam. Without extra stiffness in that beam, it would flex under the weight — and movement in the gutter causes the glass panels to shift, eventually cracking them. The Sanctuary's gutter beam has a steel reinforcement strip bonded inside the aluminium profile to prevent this deflection. It's invisible from outside, but it's the structural feature that allows the model to carry a glass roof across its full span.

The Roof: Structured Polycarbonate (16mm)

Polycarbonate sometimes gets unfairly dismissed because of its association with cheap, thin 1990s conservatory roofs that yellowed within a few years. The structured polycarbonate used in modern verandas is a very different product.

First, the material itself. Polycarbonate is a high-performance thermoplastic with exceptionally high impact resistance — it's used in bulletproof glazing, riot shields, aircraft canopies, and safety visors. It's significantly harder to break than glass of equivalent thickness. The problem outdoors, historically, was UV: without protection, UV radiation degrades polycarbonate chains, causing yellowing and hazing. Modern panels solve this with a UV-absorbing layer co-extruded into the outer surface during manufacture. It's not a coating applied afterwards that can peel or wear away — it's fused into the material. Quality panels carry a warranty against discolouration.

Multi-wall structured panels

The panels in our verandas are 16mm thick and multi-wall — not flat sheet. If you looked at a cross-section, you'd see multiple parallel internal chambers, like a very refined honeycomb. These chambers do three things: they dramatically increase the panel's stiffness and load-bearing strength relative to its weight; they provide meaningful thermal insulation (trapped air is a good insulator); and they contribute to impact resistance by allowing the panel to absorb energy as it flexes slightly rather than cracking.

The weight difference versus glass is significant. A polycarbonate roof places far less loading on the frame than a glass roof of the same area, which is why polycarbonate-roofed models don't need the steel-reinforced gutter that a glass-roofed Sanctuary does.

Tint options affect how the space feels underneath. Clear maximises light — the brightest, most open feel. Opal diffuses light softly, eliminating direct glare and creating an even, pleasant light quality. Solar Control and Heat Guard variants reduce heat gain on south and west-facing installations. Bronze gives a warm tinted midpoint. None of them affect waterproofing — all options keep you completely dry.

The Seals: EPDM Rubber Gaskets

Tucked between every glass or polycarbonate panel and the aluminium frame that holds it are rubber gaskets — thin black strips that most people never think about. They're doing more work than they get credit for.

EPDM stands for ethylene propylene diene monomer. It's a synthetic rubber chosen specifically for its outdoor durability. Natural rubber fails outdoors because ozone in the atmosphere attacks its chemical structure, causing brittleness and cracking within a few years. EPDM doesn't have this vulnerability — its molecular structure is resistant to ozone, UV, and weathering. It maintains its flexibility from well below freezing to over 120°C, resisting both hard UK winters and summer heat without hardening or softening.

The gaskets do three things: they hold the glass or polycarbonate panels securely in their channels without point-loading the glazing (distributed pressure rather than hard contact, which would risk cracking panels); they form a continuous weather seal preventing water ingress; and they provide a degree of thermal break between the cold aluminium frame and the glazing. Critically, EPDM has excellent compression set recovery — after years of being compressed between glass and frame, it springs back to its original shape rather than permanently deforming and losing its seal.

Two main gasket profiles are used. Wedge gaskets are pushed between the glass edge and the frame channel — the tapered shape means the more it's compressed, the tighter the seal. Bubble or bulb gaskets have a hollow section that deforms under compression and recovers elastically — used where there's thermal movement in the frame that needs to be accommodated without the seal breaking.

The Fixings: 316 Marine Grade Stainless Steel

The bolts, screws, and anchors that hold a veranda to your house and to its foundations are a detail that most people never ask about. On British-made models in our range, every structural fixing is 316 grade stainless steel.

There are two common stainless steel grades for outdoor use: 304 and 316. Both resist corrosion through a thin chromium oxide layer on their surface. The difference is that 316 has a 2–3% molybdenum addition, which makes its protective layer far more stable in the presence of chlorides — the salt compounds found in coastal air, road salt, and some groundwater. In non-coastal conditions, the difference matters less. But over 60 years of outdoor use in the British climate, 304 fixings can develop pitting corrosion and rust staining. 316 doesn't.

316 stainless steel is the standard for marine hardware, surgical instruments, food processing equipment, and coastal architectural metalwork — anything that needs corrosion resistance in chloride environments for long service life. In a veranda, it's the bolts you'll never see but that are still holding the structure to your wall on its 50th birthday.

The Guttering: Extruded In, Not Bolted On

All our verandas use integral aluminium guttering — the gutter channel is formed as part of the front beam extrusion itself, not attached as a separate component. This is one of the clearest markers of a quality veranda over a budget canopy.

A bolt-on plastic gutter has several ways to fail over time: the fixing clips corrode; the plastic becomes brittle with UV exposure; the gutter sags as clip spacing increases under load; the joint between gutter and structure becomes a leak point. An integral aluminium gutter has none of these failure modes. It's the same material as the frame with the same life expectancy. There's nothing to corrode, sag, or separate. Water is channelled through the beam profile to internal drainage points and routed down through the hollow posts to ground-level outlets — no external pipework, no separate component to maintain.

The drainage connects to standard UPVC downpipe fittings and can discharge at surface level or tie into underground drainage depending on your garden setup.

How It All Compares by Model

The British-made models carry longer warranties and life expectancies as a direct result of their alloy specification, marine grade coating, 316 stainless steel fixings, and manufacturing standards. The Dutch-made models are high-quality products in their own right — but they're engineered to a different specification, and the warranty and longevity figures reflect that honestly.

Frequently Asked Questions