Crittall Steel vs Velfac Aluminium for a Slim Internal Glass Partition

Where fabrication changes the price

Crittall-pattern partitions begin with a surveyed opening, then the fabricator cuts W20 or the slimmer T60 steel profiles to suit that exact size. The sections are welded, dressed, hot-dip galvanised, and powder-coated before glazing. For a single 2.4m by 2.1m screen with a door, UK fabricators commonly quote between £1,800 and £4,500 supplied, with the final number moving according to the number of glazing bars and the inclusion of an integrated door. The steel sections themselves are inexpensive; the invoice grows during welding, cleaning up each junction, and finishing the frame.

Velfac is a Danish system sold through fixed dealer networks, so the price is built in a different way. Its internal screens follow the same aluminium-timber composite logic used in its windows, and a comparable opening tends to land 15 to 30 percent below a hand-fabricated steel screen of similar size. The visual compromise sits at the perimeter. Velfac aluminium members are wider than a true W20 steel section, so the fine black-grid look associated with Crittall becomes broader and softer. An aluminium system marketed as a Crittall-style alternative may share the colour and broad layout, while the frame proportions remain those of a system product.

Frame depth and the glass it can carry

W20 steel sections have a face width of around 20mm to 25mm. That slim face still carries load because steel resists deflection at sections where aluminium would flex. A Crittall screen can therefore take larger panes with fewer intermediate glazing bars, which matters when the design calls for clear glass areas and a thin grid in the sightline.

Aluminium needs more material to achieve similar stiffness. A slim aluminium internal frame usually sits at 40mm to 60mm face width once the glazing channel and any specified thermal break are included. Velfac frames also carry a polyurethane thermal break and a timber inner face. That helps on an external wall, although on an internal screen it adds bulk around each pane.

Glass specification matters whichever frame you pick. Most internal partitions use 8mm or 10mm toughened safety glass to BS EN 12150. At 10mm thickness, toughened glass weighs about 25kg per square metre, so a full-height pane roughly 1m wide and 2.4m tall comes in near 60kg. Steel can hold that load in a narrow section, and aluminium can hold it too, provided the frame is enlarged enough to keep movement under control.

A worked cost comparison for one opening

Use a real opening as the test case: 2.6m wide, 2.4m from floor to ceiling, one 900mm hinged glass door, and the remaining fixed panes divided into three bays with horizontal bars at 600mm centres.

For the Crittall-pattern steel route, a regional fabricator quotes about £3,400 supplied for the powder-coated steel screen and door in RAL 9005 matt black, including 10mm toughened glass. Delivery adds £150 to £250 because the screen travels as heavy welded sub-assemblies. Installation by a fitter used to steel screens runs £400 to £700 for a day on site. The total comes out near £4,100.

For the Velfac aluminium route, the dealer price is about £2,600 supplied for the same opening, including glass and door. The unit travels lighter and in more pieces, so two people can carry it without a lifting frame. Installation is similar, at £350 to £600. The total comes out near £3,150.

Around £950 separates the two totals in this example. In the steel version, the eye sees 20mm bars and a denser true-divided-light grid. The Velfac unit has about 50mm of perimeter framing and a softer line around the glass. So the choice sits between a tailored steel fabrication and a lighter system product that speaks a related visual language.

What the floor underneath has to carry

Weight controls more of the installation than many quotes show. A full-height steel screen across a 3m opening can weigh 120kg to 180kg after glazing. On a solid concrete slab that figure rarely matters. On a suspended timber floor, especially a Victorian joisted floor with joists running the wrong way below the partition line, the point load can become the limiting detail.

Steel screens usually fix through a base channel bolted into the substrate, with additional head and jamb fixings. If the partition runs parallel to the joists and sits between them, the base load lands on a board span with no joist directly below. Fitters then add noggins between the joists or shift the screen by 50mm to 100mm so the base fixings hit solid timber. When that step disappears from a rushed quote, the result can be a base that flexes and a decorative finish that cracks.

The same fixing logic applies to nearby joinery. A partition is often paired with floating shelves on the adjacent wall. A floating shelf bracket pulls at the wall fixing, and a 60kg glass pane loads the floor fixing. Both rely on structure behind the visible finish. The secure route is fixing into timber or masonry, never into plasterboard or a loose board span.

Velfac aluminium is lighter per metre, which eases the floor problem without removing the need for bearing under the base channel. Even at two thirds of the weight, a glazed aluminium screen still needs a solid line below it.

The finish nobody prices carefully enough

Powder coating gives steel much of its reputation and much of its lead time. A galvanised and powder-coated W20 screen in matt black resists corrosion and holds its colour for decades indoors. The finish is applied before delivery, so a chip made on site leaves the installer using touch-up paint that rarely matches the factory coat exactly. Fabrication and coating together push lead times to six to ten weeks at many UK suppliers.

Aluminium takes powder coating to the same RAL references, and Velfac applies its coating in factory conditions as well. Its advantage is corrosion behaviour. If the coating is scratched, aluminium does not rust, so the damage stays cosmetic. A deep scratch through a steel coating exposes metal that can oxidise over years.

Door hardware

The door is where the hardware budget concentrates: pivot or hinge sets, a flush pull, and a magnetic catch usually run £120 to £400 depending on brand. The quality of those parts determines whether the door still closes cleanly after five years of use.

Measuring the opening before anyone quotes

The survey is the pricing document for both systems because both are made to measure. Take the opening at three heights and three widths, since plastered reveals are rarely square and the smallest dimension controls the frame size.

Floor finish thickness belongs in the same notes. A screen sized to the subfloor may fail to seat once the underlay beneath a sisal stair runner or a 22mm engineered board has gone down. Any finished floor build-up around the partition base changes the available height.

Head deflection is the measurement that often gets missed. A ceiling can drop several millimetres across a 3m span under live load. A rigidly fixed full-height screen can bind at the head or pass that movement into the glass.

Steel fabricators usually design the head with a small expansion gap hidden behind a trim. Velfac uses a packed head channel for the same purpose. A quote should state which head detail is included, because a screen fixed hard at top and bottom has no planned movement allowance and can develop a hairline glass crack during its first heating season.

The survey also sets the door swing. That detail feeds back into hardware choice, threshold clearance, and the way the base channel meets the floor finish.

Bar layout and glazing weight follow from the same visit. More bars can change the fabrication time, and larger panes alter the load that returns to the floor. A quote issued without a site survey can miss the smallest opening dimension, the head movement, and the bearing required under the base channel.

The line in the room

A 20mm steel sightline reads differently from a 50mm aluminium perimeter once the screen is installed and painted black. The steel route also means a welded screen made to the measured opening. Aluminium cuts the weight and makes handling easier on site, and because it does not rust, a scratch stays a scratch. The trade is the broader frame, which pulls the look away from the original Crittall grid.

The gap in the worked example came to about £950, set against a partition that someone will look at every day for twenty years. What none of the neat drawings tend to settle is exactly how the head channel will conceal its movement gap where the trim, the plaster, and the top of the glass all arrive at the same line, and that joint is usually decided on site rather than on paper.