Single Piece Manufacturing. No Joints, No Leaks

Complex & Bay

Window Cills

Bay windows and complex angles need precision. Our segment-by-segment designer lets you capture exact dimensions for 3-segment, 5-segment, and curved bay cills. Every cill is manufactured as a single seamless piece in 2mm marine-grade aluminium. No joints. No leaks.

Trusted by 1000+ contractors

3-5 day turnaround

Free delivery over €150

Made in Dublin

Enter measurements segment by segment

See exact cill shape before ordering

Single-piece, no joints or leaks

Every complex cill is handmade as a single seamless piece in our Dublin workshop. No interpretation. No surprises.

Order Without Second Guessing

Watch Demo

No credit card required • Segment-by-segment designer • Single-piece manufacturing

2mm

Marine-Grade Aluminium

1 Piece

Seamless Manufacturing

3-5

Business Days Turnaround

Joint Failures

Single Piece Precision

Drawings Look Simple.

But They Cause Mistakes.

You draw a line. You add a note. You think it is clear. But the person reading it sees something different. CILLS changes that.

Handmade as a single seamless piece

Made in our Dublin workshop

No interpretation errors

No surprises on delivery

Start Designing Free

Watch Demo

1 Piece

No joints, no leaks

Choose Your Service Level

Pick the plan that suits your workflow - self-service, split responsibility, or full-service.

You Measure -
We Manufacture

Measure in-app, we fabricate. Collect or delivery options available.

What's included:

Guided measuring with 3D preview to avoid errors.

Made-to-measure aluminium cills, flashings and trims.

Fast manufacture - choose factory collection or delivery.

Start Measuring

Perfect for builders who want speed and full control.

We Measure -
You Fit

Book a site visit. We take the measurements and deliver ready-to-fit parts.

What's included:

On-site measurement using calibrated devices for exact RAL matching.

Perfect for complex bay and angled cills.

Delivered to site - parts ready for your installers.

Book a Measure

Ideal for retrofit contractors who want professional measuring without the hassle.

We Measure -
Deliver & Fit

Full service: measurement, manufacture, delivery and professional fitting.

What's included:

End-to-end service - we manage the process and fit on-site.

Engineer-validated installation and QA on completion.

Perfect for homeowners or busy contractors who want turnkey solution.

Request Full Service

Full peace of mind - we handle everything from A to Z.

The Real Problem Is Not Skill

Why Complex Cills Fail More Often

Bay window cills involve multiple angles that compound errors. A small mistake on one segment affects every segment after it.

Complex Angles = Costly Remakes

Bay window cills require precise angle calculations. A 2° error compounds across segments, resulting in cills that don't fit. Remake costs for bay cills often exceed €400.

€400+

Average bay cill remake cost

Multi-Point Cold Bridging

Each segment joint in a poorly designed bay cill creates a thermal bridge. Victorian bay windows can have 5+ potential cold bridge points if measured incorrectly.

5×

More cold bridge risk than standard cills

Joint Failures & Water Ingress

Multi-piece bay cills rely on sealant at every joint. Sealant fails over time. Single-piece manufacturing eliminates joint failures entirely.

100%

Of joint failures eliminated with single-piece

Measure Right, Order Once

Complex Cill

Measurement Tips

Bay windows require extra care. Here's how to get it right first time —or why you might want our professional measurement service.

Measure Each Segment Individually

Take the full length of each bay segment separately. Don't try to calculate total span—our system handles the geometry.

Use a Digital Angle Finder

Bay window angles are rarely exactly 45° or 135°. A £20 digital angle finder prevents hundreds in remake costs.

Account for External Insulation at Every Segment

EWI systems wrap around bay windows. Each segment projection must account for the insulation depth at that point.

Consider Our 'We Measure' Service

Complex bays with curved profiles or 5+ segments benefit from professional on-site measurement. It's our most popular service level.

±1°

Angle precision

Every Bay Configuration Supported

From simple three-segment bays to complex Victorian curves, design any configuration.

◇

3-Segment Bay

Classic three-panel bay window. Front panel and two angled sides. Most common configuration.

⬡

5-Segment Bay

Five-panel bay with multiple angles. Common in Victorian and Edwardian properties.

◠

Curved Bay

Smooth curved profile for bow windows. Manufactured to your exact radius specification.

▢

Box Bay

Square projection with 90° returns. Clean modern aesthetic for contemporary builds.

Purpose-Built for Complex Cills

Every feature designed specifically for multi-angle, multi-segment cills.

Segment-by-Segment Design

Complex bay windows broken into simple steps. Add segments one at a time, each with its own length, angle, and projection.

Visual Angle Calculator

Enter your angles and the app calculates exact dimensions. No more trigonometry on site or hoping you got it right.

Single Piece Manufacturing

Your entire bay cill manufactured as one seamless piece in 2mm marine-grade aluminium. No joints, no leaks, perfect aesthetics.

Full RAL Colour Selection

Match windows, doors, or any existing finish with the complete RAL Classic library. 3D preview shows exact colour before ordering.

Technical Drawings Included

Every complex cill order includes detailed technical drawings for installation reference, client sign-off, and quality assurance.

30+ Year Coating Warranty

Premium polyester powder coat finish with 30+ year lifespan. Complete peace of mind for your clients and your reputation.

Technical Specifications

Material

Marine-Grade Aluminium

Thickness

2mm Standard

Maximum Span

4000mm

Projection Range

50mm - 400mm

Finish

Polyester Powder Coat

Colour Options

Full RAL Classic Range

Manufacturing

3-5 Business Days

Warranty

30+ Year Coating Life

Customer Reviews

Trusted by Contractors Across Ireland

See why builders and installers are switching to Cills.ie for their

aluminium cill orders.

"We specialise in Victorian restorations with complex bay windows. The segment-by-segment designer finally makes measuring these manageable. Single-piece delivery is a game-changer—no more joint failures."

James Brennan

Director, Brennan Heritage Restorations

Dublin

"Had a 7-segment curved bay that would have been impossible to measure ourselves. Booked the 'We Measure' service and received a perfect single-piece cill. Worth every cent."

Aisling Connolly

Project Manager, Connolly Construction

Cork

"The angle calculator is brilliant. I used to spend 30 minutes doing trigonometry for each bay. Now I just enter the angles and the app does the rest. Massive time saver."

Dermot Flynn

Owner, Flynn Window Installations

Galway

"Switched from jointed bay cills to single-piece from Cills.ie. Zero callbacks in 18 months. My installers love them because they just drop in perfectly."

Ciara Walsh

Operations Manager, Walsh Windows & Doors

Limerick

Stop Guessing. Order with Confidence.

Complex bay cills made simple. Design segment by segment, receive a single seamless piece.

Start Designing Free

Book Measurement Service

Custom Powder-Coated Colours for Every Aluminium Window Cill

Match any facade with RAL-certified powder coating. Our aluminium window cills, flashings, cappings,

and trims are made-to-measure and finished in your exact colour.

Match any facade with RAL-certified powder coating. Our aluminium window cills, flashings, cappings,

and trims are made-to-measure and finished in your exact colour.

RAL 7016

Slate Grey

RAL 7015

Anthracite Grey

RAL 7032

Pebble Grey

RAL 7044

Silk Grey

RAL 8028

Terra Brown

RAL 9003

Signal White

Why Colour with Cills.ie?

Any RAL colour: hundreds of architectural finishes with UV-stable,

durable coating.

Any RAL colour: hundreds of architectural finishes with UV-stable,

durable coating.

Perfect matching: on-site measuring devices capture the exact RAL

shade for windows and facades.

Perfect matching: on-site measuring devices capture the exact RAL

shade for windows and facades.

Made-to-measure aluminium: precision fabrication for cills, bay/angled

cills, parapet cappings & weatherproof flashings.

Made-to-measure aluminium: precision fabrication for cills, bay/angled

cills, parapet cappings & weatherproof flashings.

Retrofit-ready: designed for SEAI external wall insulation systems with

clean, watertight detailing.

Retrofit-ready: designed for SEAI external wall insulation systems with

clean, watertight detailing.

Order in minutes: measure, preview colour, and track manufacturing &

delivery inside the app.

Order in minutes: measure, preview colour, and track manufacturing &

delivery inside the app.

Open Colour Picker

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Frequently Asked

Questions

Have another question? Please contact
our team!

What makes complex cills different from standard cills?

Complex cills involve multiple angles, segments, or curves—typically for bay windows, oriel windows, or non-rectangular openings. They require precise angle calculations and are manufactured as single seamless pieces to eliminate joints and potential failure points.