WINDOW SYSTEMS

Made to measure window systems

Our wide range of window systems are designed to suit a broad variety of architectural designs. Choose from our slim casement windows to a steel look design from the Legacy Range. All of the Sieger window systems are fully thermally broken for high levels of insulation with a choice of ironmongery.

Bespoke made to order

Ten alternative systems

Design, supply & installation

Southern England coverage

Bring more light into your home

Our bespoke window systems combine slim aluminium frames, high-performance glazing and flexible configurations to maximise natural light, views and architectural impact. Designed around each individual project, they offer a refined balance of appearance, performance and everyday functionality.

Compare window systems

Choosing glazing systems for a premium property involves more than aesthetics, with performance, efficiency, sightlines and compliance all playing a key role.

Picture windows

Large fixed windows designed to frame external views and maximise natural light with minimal visual interruption.

Sightline

Slimline / frameless

Max panel width:

Project dependent

Max panel height:

Project dependent

Oriel windows

Frameless structural glass projections that create panoramic views while bringing light in from multiple directions.

Sightline

63mm / 72mm fixing

Max panel width:

Up to 5740mm*

Max panel height:

Up to 5000mm*

Gable end windows

Bespoke frameless glazing designed to fill pitched gable elevations with natural light and uninterrupted views.

Sightline

63mm / 72mm fixing

Max panel width:

Project dependent

Max panel height:

Project dependent

Eaves windows

Frameless up-and-over glazing that connects vertical glass with the roofline for a seamless architectural finish.

Sightline

63mm / 72mm fixing

Max panel width:

Up to 5740mm*

Max panel height:

Up to 5000mm*

Sieger HD casement windows

A heavy-duty aluminium casement system designed for larger openings with secure, flexible opening configurations.

Sightline

58mm / 70mm frame

Max panel width:

1400mm

Max panel height:

2400mm

Innovare windows by Sieger

A flush-glazed aluminium window with edge-to-edge glass, concealed framing and Uw values from 1.1 W/m²K.

Sightline

Edge-to-edge glass

Max panel width:

2200mm

Max panel height:

1600mm

Sieger legacy windows

A slim steel-look aluminium window combining traditional character with modern thermally broken performance.

Sightline

58mm

Max panel width:

2100mm

Max panel height:

2100mm

Sieger flush casement windows

An ultra-minimal flush casement window combining a slim 45mm sash with secure, weather-tested performance.

Sightline

45mm sash

Max panel width:

1400mm

Max panel height:

1400mm

Sieger slim casement windows

An award-winning aluminium casement window combining 65mm sightlines with Uw values from 1.1 W/m²K.

Sightline

65mm

Max panel width:

1200mm

Max panel height:

1300mm

Sieger 70 TT windows

A contemporary tilt and turn window combining large opening panels with thermally broken aluminium framing.

Sightline

Slim frame

Max panel width:

1300mm

Max panel height:

2400mm

System comparison	Picture	Oriel	Gable End	Eaves	HD Casement	Innovare	Legacy	Flush Casement	Slim Casement	70 TT
Application	Fixed	Structural	Structural	Structural	Opening / fixed	Opening / fixed	Opening / fixed	Opening / fixed	Opening / fixed	Tilt & turn
Sightline / profile	Slim / frameless	63 / 72mm fixing	63 / 72mm fixing	63 / 72mm fixing	58 / 70mm frame	Edge-to-edge glass	58mm	45mm sash	65mm	Slim aluminium
Max panel width	Project dependent	Up to 5740mm*	Project dependent	Up to 5740mm*	1400mm	2200mm	2100mm	1400mm	1200mm	1300mm
Max panel height	Project dependent	Up to 5000mm*	Project dependent	Up to 5000mm*	2400mm	1600mm	2100mm	1400mm	1300mm	2400mm
Thermal performance	System dependent	From 1.1 W/m²K	From 1.1 W/m²K	From 1.1 W/m²K	Thermally broken	From 1.1 W/m²K	From 1.5 W/m²K	Thermally broken	From 1.1 W/m²K	Thermally broken
Opening options	Fixed	Fixed	Fixed	Fixed	Multiple	Side / top hung	Multiple	Multiple	Side / top hung	Tilt & turn
Security	Project specific	Structural glazing	Structural glazing	Structural glazing	PAS 24	PAS 24	PAS 24	PAS 24	PAS 24	Concealed locking
Glazing options	Double / triple	Performance glass	Performance glass	Performance glass	Double glazed	Performance glass	Double glazed	Double glazed	Up to 44mm	Up to 40mm

Window solutions for every setting

From large fixed picture windows and slim opening casements to projecting oriel glazing, glazed gable ends and frameless eaves windows, our window systems can be designed around the architecture of your home. Bespoke sizes, shapes, opening configurations and glazing specifications provide the flexibility to maximise natural light while creating a cohesive glazing design.

Performance without compromise

Our window systems combine slim aluminium or frameless detailing with high-performance glazing, thermally broken construction and secure hardware. Each system can be specified around the thermal, security and architectural requirements of the individual project.

From

45mm

sash profiles

From

1.1 Uw values

Up to

2.4m

opening height

All

PAS 24

options available

Double or

triple

glazing

Who we can help

For homeowners

Bespoke window systems that maximise natural light, improve performance and complement the character of your home.

For architects

Bespoke window systems with flexible configurations, slim profiles and technical support for architectural projects.

For builders & developers

Bespoke window systems with reliable performance, flexible specifications and support from design through to installation.

Sieger windows in real homes

August, 2026

Bosham

July, 2026

Burdon Lane

July, 2026

Finnmoor

July, 2026

Rosegarth

July, 2026

Bentley Manor

July, 2026

Hatcham Park Road

Our easy 5-step process

1. Consult

Discuss your project
and objectives

2. Specify

Choose the right system
and configuration

3. Survey

Accurate site survey
and measurements

4. Manufacture

Precision engineering
in our UK factory

5. Install

Expert installation
by our own team

Serving the home counties & the south-west of England

Local expertise, fast response and nationwode peace of mind.

Serving the home counties & the south-west of England

Local expertise, fast response and nationwode peace of mind.

FAQs

Find answers to some of the most common questions about our made-to-measure window systems..

What types of window systems are available?

Sieger offers fixed picture windows, structural glass windows, casement windows, flush-glazed windows, steel-look windows and tilt and turn systems for a wide range of architectural projects.

What are the benefits of aluminium windows?

Aluminium provides strong, durable frames with slim profiles, allowing larger areas of glass while supporting excellent thermal, weather and security performance.

How slim can aluminium window frames be?

This depends on the system selected. The Sieger Flush Casement Window features a slim 45mm sash, while other systems offer different profiles to suit their design and performance requirements.

Are aluminium windows energy efficient?

Yes. Sieger window systems use thermally broken frames and insulated glazing, with selected systems achieving Uw values from 1.1 W/m²K.

Are Sieger window systems secure?

Yes. Selected Sieger aluminium window systems are PAS 24 certified and incorporate secure locking hardware for residential and commercial applications.

Can window systems be made to measure?

Yes. Sieger window systems are designed around the dimensions, glazing requirements, opening style and architectural details of each individual project.