Cortizo 4900 Sliding HI Doors: A Review

The Cortizo 4900 Sliding HI is the in-line sliding window and door system Cortizo describes as a standard slider with casement-like performance. It sits alongside the 4700 Sliding Patio in Cortizo's range, and the slim-sightline Cor Vision family is the step to take when the narrowest junction is the goal. We fabricate and fit the 4900 regularly from our Uxbridge workshop, and this review sets out how it performs, where it earns its place against the 4700, and who should specify it.

What Is the Cortizo 4900 Sliding HI?

The 4900 Sliding HI is a conventional in-line aluminium slider, meaning the sashes glide past each other on parallel tracks rather than lifting clear for operation. What sets it apart from the 4700 Sliding Patio is sealing and layout: the 4900 reaches class 4 air-tightness, runs a slimmer 35mm central junction and comes in more track layouts, including 4-track. Sashes run up to 2.2m wide by 3m high at 240kg, with glazing units from 24mm to 36mm.

Sightlines and Glass Area

The 4900's central junction is 35mm, slimmer than the 47mm interlock on the 4700 Sliding Patio, though wider than the 20mm junction on Cor Vision. For most household rear extensions, that balance is the right one: the sightline is slim by conventional standards, and the system's air-tightness and locking matter more day to day than shaving a few extra millimetres off the frame.

Thermal Performance

Every 4900 installation we specify takes A-rated double glazing as standard, with the energy category confirmed at survey once the exact glazing and configuration are set. Cortizo quotes Uw from 1.2 W/m²K for the 4900, and its standout figure is air-tightness: class 4, which keeps draughts out on an exposed elevation. On U-value alone the 4700 Sliding Patio does slightly better, at Uw from 1.0 W/m²K, so where insulation is the deciding figure the 4700 is the stronger choice. Both systems are rated for sound reduction up to Rw 40dB.

Security and Hardware

The 4900 is specified with multi-point locking hardware as standard, with the exact security specification confirmed at survey based on the configuration ordered. Where a project needs a PAS 24 rated door, such as a new dwelling under Approved Document Q, the 4700 Sliding Patio or the standard Cor Vision Sliding is the Cortizo slider to specify, as both can be specified to PAS 24 (the 4700 is tested to PAS 24:2016).

Colour and Finish

Like the rest of the Cortizo range, the 4900 is available across the full RAL colour spectrum in powder-coat, including a dual-colour option for a different finish inside and out. Anthracite grey remains the most requested colour on the projects we fit, though the full palette is available to match any elevation.

How It Compares to the 4700

Both systems share Cortizo's in-line sliding mechanism, colour range and multi-point locking, so the buying decision comes down to the opening. The 4700 Sliding Patio takes larger and heavier sashes (up to 2.5m wide by 3m high, at 280kg in-line or 300kg lift-and-slide), comes in a lift-and-slide version and has the better U-value, from 1.0 W/m²K against the 4900's 1.2. The 4900 answers with a slimmer 35mm central junction against the 4700's 47mm interlock, class 4 air-tightness and more track layouts, including 4-track. For the widest, heaviest panels, specify the 4700; for a standard-sized opening where a finer junction, a tighter seal or an extra track matters, the 4900 earns its place.

Our Verdict

The Cortizo 4900 Sliding HI is a well-judged performance slider rather than a flagship statement piece, and that is exactly its strength. It brings casement-like air-tightness and a slimmer junction than the 4700 without moving into the sightline-focused Cor Vision tier, which makes it the system we recommend for standard-sized openings on exposed or draught-prone elevations, and for layouts that need a third or fourth track. Where the panels are very large or heavy, or lift-and-slide operation is wanted, the 4700 Sliding Patio is the better fit.

We fabricate and install the Cortizo 4900 Sliding HI in-house at our Uxbridge workshop, cutting, machining and assembling every unit to the exact opening measured on site. Every installation is FENSA registered and carries a 10-year CPA insurance-backed guarantee.

Frequently Asked Questions

What does "HI" mean in Cortizo 4900 Sliding HI?

HI is part of Cortizo's system name for the 4900's thermally broken profile. On Cortizo's own figures the 4700 Sliding Patio insulates slightly better, at Uw from 1.0 W/m²K against the 4900's 1.2 W/m²K. What the 4900 adds over the 4700 is class 4 air-tightness, a slimmer 35mm central junction and more track layouts, including 4-track.

Is the Cortizo 4900 Sliding HI a lift-and-slide door?

No. The 4900 Sliding HI is a conventional in-line slider, with the sashes gliding past each other on parallel tracks. If you want lift-and-slide, the Cortizo option is the lift-and-slide version of the 4700 Sliding Patio, with sashes up to 2.5m wide by 3m high at 300kg; see our Cortizo lift-and-slide page. The slim-sightline Cor Vision family is the system to look at if an even narrower junction is the priority.

When should I choose the 4900 over the standard 4700?

Choose the 4900 when the sashes sit within its 2.2m by 3m limit and you want class 4 air-tightness on an exposed elevation, a slimmer 35mm central junction, or a 4-track layout. Choose the 4700 when the sashes need to be larger or heavier (up to 2.5m by 3m), when you want lift-and-slide operation, or when the lower U-value is the priority, since the 4700 reaches Uw from 1.0 W/m²K against the 4900's 1.2.

What glazing does the Cortizo 4900 Sliding HI take?

The 4900 takes glazing units from 24mm to 36mm thick. We specify A-rated double glazing as standard, with the exact specification and configuration confirmed at survey based on the size and orientation of your opening.

Does the Cortizo 4900 Sliding HI come with a guarantee?

Yes. Every Cortizo 4900 Sliding HI installation we carry out is FENSA registered and backed by a 10-year CPA insurance-backed guarantee, covering the workmanship of the fit.