Crittall-style steel windows in London (2026): costs, specs and the honest trade-offs

Steel-framed, black-gridded glazing — the "Crittall" look — comes two ways in London, and the right one depends on where it's going. Authentic Crittall (and other genuine steel windows) is the real article for heritage elevations, but it's single-glazed-derived, slower to deliver, and harder to make thermally efficient. Steel-look aluminium systems mimic the slim black profiles with modern double glazing, far better thermal performance, and shorter lead times — usually the sensible choice for a new opening or an internal screen. Internal Crittall-style screens, the most popular use of the look in London, run roughly £1,250–£3,600 per square metre installed. This guide sets out which to use where, the thermal trade-offs, and how a builder handles the look on a period home.

Authentic Crittall vs steel-look aluminium

The two are easy to conflate and important to separate. Genuine steel windows — Crittall being the best-known name, with makers like Clement also in the field — are rolled-steel frames, the original article on which the look is based; they're the right answer where a heritage elevation needs a true like-for-like, but they derive from single-glazed construction, carry longer lead times (often three to five months), and need careful detailing to reach modern thermal standards. Steel-look aluminium systems — from the likes of Reynaers and similar — reproduce the slim black sightlines in a thermally broken aluminium frame with modern double glazing; they perform far better on heat loss, arrive quicker (typically a couple of months), and are usually the pragmatic choice for a new internal screen or a non-heritage opening. The headline question is simple: are you matching protected historic windows, or creating the look afresh?

The thermal reality on an external elevation

This is where the romance meets physics. Original-style single-glazed steel has a poor thermal value — heat pours out and condensation forms readily on the cold metal in winter. A thermally broken modern equivalent is dramatically better, which matters because replacement windows generally have to meet the Building Regulations Part L standard of a 1.6 watts-per-square-metre-kelvin whole-unit figure. Where a window faces the street within a conservation area, the council may accept a like-for-like steel replacement on character grounds, while a switch to aluminium usually needs evidence that the new units match the slim sightlines and perform thermally. The practical reading: externally, steel-look aluminium gives you the appearance without the cold-frame condensation, unless heritage rules specifically require genuine steel.

Internal screens — the high-value, low-risk use

The most rewarding place to use the look isn't a window at all — it's an internal screen. A steel-style glazed partition between a kitchen and a dining area, or framing a hallway, delivers the whole aesthetic with none of the weather, thermal or planning headaches an external window carries. Because it's internal, there's no U-value to meet, no condensation risk, and usually no consent needed (unless the building is listed). A bespoke powder-coated internal screen runs about £1,250–£3,600 per square metre installed, depending on the size, the number of opening doors and the glazing. For most London homeowners chasing the Crittall look, an internal screen is where the budget does the most work for the least risk.

Costs and lead times at a glance

What to budget and how long to wait:

• Authentic steel windows: the premium route, with lead times commonly running three to five months from order — plan the programme around them.
• Steel-look aluminium windows: a shorter wait, typically around two months, and easier to hit modern thermal standards.
• Internal steel-style screens: £1,250–£3,600 per square metre installed, powder-coated to the colour you choose.

Order early whichever you pick — steel-framed glazing is a specialist-fabrication item, not something pulled off a shelf, so a late order is a late job.

Conservation areas and listed buildings

On a protected elevation the rules shape the choice. In a conservation area, a like-for-like steel replacement of existing steel windows is generally the path of least resistance, because it preserves the character the designation protects; moving to aluminium tends to require showing that the replacement matches the original sightlines and meets the thermal requirement. On a listed building, expect to need listed building consent for any window change, and to be steered firmly toward genuine steel that matches what's there. The thread is consistency: the more historic and protected the elevation, the more the answer tilts toward authentic steel, detailed to perform as well as it can within those constraints.

The builder's part

Steel-style glazing lives or dies on the install detail, and that's where a builder earns their place. The opening has to be formed and squared precisely, because slim steel frames are unforgiving of a wall that's out; the structural support above the opening has to be right; the frame has to be set, sealed and flashed so water and draughts are kept out; and an internal screen has to be fixed plumb into a sound, prepared opening. PrimeCraft Surface Solutions forms and prepares the opening, coordinates the specialist glazing supplier, and fits and finishes the surround — pricing the screen or window as its own line so you can see exactly what the glazing costs against the building work around it.

Closing CTA

Whether you want the look on a window or as an internal screen changes the cost, the lead time and the rules — so it's worth scoping properly before you order anything specialist. PrimeCraft Surface Solutions advises on authentic-versus-look-alike for your situation, forms and finishes the opening, and coordinates the glazing supplier — working throughout London and out into the neighbouring counties. Set up a free site assessment, and the right route for your home and your elevation becomes clear.