The Hidden Problem That's Costing Irish Builders Time and Money
You've been there. It's 7am on a wet Tuesday morning. The client's been on your back about when the windows are going in. The insulation's done, the render crew is booked for next week, and you still don't have the cills.
You ring your usual supplier. "Two to three weeks," they say. "And we'll need you to fill out a spreadsheet with all the measurements. Can you email it over?"
So you pull out your phone, try to remember what dimensions you took last Thursday, scribble them onto the back of an envelope, and spend your lunch break typing them into a spreadsheet. You email it. You wait. You chase. You wait some more.
When the cills finally arrive, two of them are wrong. One's 50mm too short. Another has the wrong RAL colour. The render crew is already on site.
Sound familiar?
This is the reality for contractors and builders across Ireland. And it's exactly the problem we built the Cills app to solve.
What Actually Goes Wrong With Window Cills?
Before we talk solutions, let's be honest about the problems. Because if you've worked on retrofit or new build projects in Ireland, you've probably experienced at least one of these:
Problem 1: The Measurement Nightmare
Window cills aren't complicated. But getting the measurements right? That's where projects fall apart.
You're on site with a tape measure. You've got 15 windows to measure. Each one needs at least 6 different dimensions – upstand, projection, length, returns, drip edge, fascia. That's 90 measurements to record accurately.
Now add in the pressure. The site is busy. Someone's asking you questions. You're trying to hold the tape with one hand and write with the other. It's raining.
By the time you get back to the office, your notes look like a doctor's prescription. Which window was number 7 again? Was that 1200mm or 1020mm?
How the Cills App Fixes This:
The app walks you through each measurement step by step. Interactive 3D diagrams show you exactly where to place your tape. You enter the numbers directly into your phone – no scribbled notes, no transcription errors.
Every measurement is validated in real-time. Enter something that doesn't make sense? The app flags it before you leave site. No more discovering mistakes three weeks later when the wrong cill arrives.
Problem 2: The Spreadsheet Hell
Even if you get the measurements right on site, you still need to communicate them to your supplier. That usually means:
Typing everything into a spreadsheet
Attaching photos with vague labels like "IMG_4521.jpg"
Writing long emails explaining which cill goes where
Waiting for someone to call you back with questions
Repeating yourself three times
It's not 1995. Why are we still doing business this way?
How the Cills App Fixes This:
There's no spreadsheet. No email attachments. No phone tag.
You create a project in the app. You add your measurements directly. You attach photos to each window – the app knows exactly which photo belongs to which cill. You tap "Submit for Review" and you're done.
Your entire order history lives in one place. Need to reorder the same cill you used on a project six months ago? It's all there. No hunting through email threads.
Problem 3: The Bay Window Headache
Standard rectangular cills are straightforward. Bay windows? That's where things get painful.
Bay windows have multiple segments at different angles. Each segment needs its own measurements. The angles need to be precise – a degree or two off and the joints won't close properly. And heaven help you if you're trying to explain a complex bay window configuration over the phone.
Most suppliers struggle with bay windows. Some won't even quote them. Others add weeks to the lead time and charge a premium for "complexity."
How the Cills App Fixes This:
We built the app specifically to handle complex cills. The bay window designer lets you:
Add as many segments as you need
Specify exact angles (90°, 135°, 120°, or any custom angle)
Preview how the finished cill will look
See exactly how segments connect together
No phone calls. No confusion. The app captures everything our manufacturing team needs to get it right the first time.
Problem 4: The Colour Matching Chaos
You've specified RAL 7016 to match the windows. The cills arrive. They're... grey. But not quite the right grey. They're RAL 7015 – close, but not close enough.
Now what? Send them back? Install them and hope the client doesn't notice? (They will.)
Colour mismatches happen because of miscommunication. Someone writes "anthracite grey" instead of the RAL code. Someone mishears "7016" as "7015" on the phone. Someone assumes "dark grey" means the same thing to everyone.
How the Cills App Fixes This:
You select your RAL colour in the app. There's no ambiguity. You see the exact colour on screen. You can preview how it looks against different backgrounds. The colour code is locked in – it can't be misheard or mistyped.
And if you're not sure which colour to choose? The app shows the most popular options for Irish projects. RAL 7016, RAL 9005, RAL 7016 – these aren't random selections. They're the colours that match what window manufacturers are actually using.
Problem 5: The EWI Calculation Confusion
External wall insulation changes everything. Suddenly your cills need to project 150-300mm instead of 50-80mm. But how much projection exactly?
It depends on:
Your existing wall thickness
The insulation depth (80mm? 100mm? 150mm?)
The render system (another 10-15mm)
How much overhang you want past the insulation face
Get it wrong and water drips onto your expensive new insulation. Within a year, you've got algae staining. Within five years, the render starts failing.
How the Cills App Fixes This:
The app has EWI projects built in. When you're measuring for an external insulation project, it prompts you for the information that matters:
Insulation depth
Expected render thickness
Desired overhang
Then it calculates the projection you need. No mental arithmetic. No forgetting to add the render thickness. No expensive mistakes.
The Real Problems With Traditional Cill Materials
It's not just the ordering process that's broken. The materials themselves cause problems.
Timber Cills: The Maintenance Trap
Timber looks great on day one. By year five? You're looking at:
Flaking paint
Water ingress
The beginnings of rot
In coastal areas, salt spray accelerates the decay. In shaded areas, moss and algae take hold. Either way, you're repainting every 2-3 years or watching your cills deteriorate.
That's fine for a DIY homeowner with time on their hands. For a professional project? It's a callback waiting to happen.
Concrete and Stone: Heavy, Cold, and Cracking
Traditional stone cills have their place – period properties, heritage buildings. But for modern construction?
They're heavy. They need specialist lifting on larger sizes. They're thermally conductive – creating cold bridges that contribute to condensation. And in Irish weather, the freeze-thaw cycle eventually cracks them.
PVC: Cheap Today, Brittle Tomorrow
PVC cills are cheap. That's about the only thing they have going for them.
After 10-15 years of Irish sun and rain, they become brittle. The colour fades. They yellow. And good luck finding a replacement that matches when one cracks – the manufacturer probably changed the formulation years ago.
Aluminium: The Material That Actually Works
Aluminium solves these problems:
The Problem | How Aluminium Fixes It |
|---|---|
Rot and decay | Aluminium doesn't rot. Ever. |
Thermal bridging | Powder coating provides insulation |
Colour fading | UV-stable finish lasts 30+ years |
Weight and handling | Lightweight – easy one-person install |
Colour matching | Any RAL colour, matched exactly |
Maintenance | Zero. Wipe clean occasionally. |
Understanding What You're Measuring
A (Upstand Height) – The vertical edge at the back that tucks behind your window frame. Usually 20-30mm. For EWI projects, go 25-40mm to allow the render and mesh to lap over.
B (Projection Depth) – How far the cill sticks out from the wall. This is the critical dimension for EWI. Too short and water hits your insulation. For external insulation, calculate: insulation depth + render + 50mm overhang.
DE (Drip Edge) – The front nose that throws water clear of the wall. This is what prevents staining on your render.
F (Fascia Depth) – The vertical face at the front. Visible from ground level. Usually 40-50mm.
G (Opening Width) – The width of your window opening at cill level. Measure between the reveals.
H (Overall Length) – Total length including returns. Usually G plus returns on each side.
J (End Returns) – The turned-down ends. Typically 50mm each side, but depends on your detail.
A Real Measurement Sheet
Here's what a completed project looks like:
All dimensions in millimetres
The External Insulation Reality
If you're working on SEAI-funded retrofits, external wall insulation is probably involved. And that means your cill requirements change dramatically.
What Happens When You Get It Wrong
We've seen it too many times:
Someone measures for cills before the insulation goes on
They order based on the existing wall face
Insulation adds 100-150mm to the wall thickness
The cills now sit flush with (or behind) the insulation face
Water runs off the window, down the cill, and drips onto the insulation
Within months: algae staining, green streaks, unhappy clients
This isn't a minor issue. Render failures from water damage can cost thousands to repair. And the root cause? A cill that's 100mm too short.
How to Get EWI Cills Right
Wait until insulation is installed before measuring. Seriously. The boards need to be on the wall before you take final measurements.
Calculate your projection properly:
Measure from window frame to insulation face
Add render thickness (typically 10-15mm)
Add overhang (minimum 40mm, ideally 50mm)
Specify the right upstand. The mesh and render need to lap onto the cill upstand. 25-40mm gives the EWI installer room to create a proper seal.
Don't forget end caps. Factory-fitted end caps seal the cill ends. Without them, water tracks along the cill and behind your insulation.
Common Mistakes (And How to Avoid Them)
After years of manufacturing cills for Irish projects, we've seen every mistake. Here are the ones that keep happening:
❌ Measuring before insulation is complete The insulation adds significant depth. Measure after it's on.
❌ Forgetting to account for render thickness That's another 10-15mm. It matters.
❌ Ordering without end caps Water will find its way in. Factory-fit them.
❌ Getting bay window angles wrong Measure the actual angle, don't assume it's 135°. Use the app's angle guide.
❌ Specifying colour by name instead of RAL code "Anthracite grey" can mean different things. RAL 7016 is unambiguous.
❌ Using the wrong sealant Check with your EWI system supplier. Some sealants don't bond to aluminium.
Why We Built the Cills App
We got tired of the back-and-forth.
Contractors would call with measurements. We'd type them into our system. They'd arrive differently from how they were spoken. Mistakes happened. Cills arrived wrong. Everyone's time was wasted.
So we built something better.
The Cills app puts you in control:
✅ Measure on site with guided 3D diagrams
✅ Enter dimensions directly – no transcription errors
✅ See your order before you submit
✅ Track progress from manufacturing to delivery
✅ Reorder easily from your project history
✅ Get help when you need it – upload drawings, request assistance
It's not a complicated concept. It's just doing what should have been done years ago: making it easy to order the right cills, first time.
Frequently Asked Questions
How long do aluminium window cills last? 30+ years with proper installation. The powder-coated finish is UV-stable and won't fade in Irish conditions.
Can I order just one cill? Yes. There's no minimum order. Need one cill for a repair job? No problem.
What if I'm not sure about measurements? Use the "I need assistance" option in the app. Upload your drawings or photos and our team will help you spec it correctly.
What about bay windows and complex shapes? This is what we do. The app handles bay windows, angled cills, multi-segment configurations – anything you need.
Do you deliver nationwide? Yes, we deliver across Ireland. Track your order status directly in the app.
What if I make a mistake in the app? Edit your measurements before you submit. The app validates entries in real-time, catching obvious errors before they become expensive mistakes.
Ready to Stop Fighting With Spreadsheets?
Getting aluminium window cills shouldn't be complicated. It should be:
Measure – with clear guidance on what to measure and where
Enter – directly into an app that validates your inputs
Submit – with confidence that your order is correct
Receive – precision-manufactured cills that fit first time
That's it. No spreadsheets. No phone tag. No wrong cills arriving on site.
Get started in under a minute:
📱 Download the app: iOS | Android
💻 Or create your account at: app.cills.ie
Your next project deserves cills that fit.
Aluminium Cills Ireland - Custom Manufacturing for EWI
Step-by-step guide to ordering custom aluminium cills for external wall insulation projects across Ireland.
Daniel Ganea
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