Why Custom Windows and Doors Cost More
Avoid Wasting Money on Custom Windows
One of the most common mistakes in designing a house is not about aesthetics or structure. It is about something that seems trivial: the openings for windows and doors.
Paradoxically, the places where you assume it will be fixed during construction are exactly where serious money is lost. And no, it is not the joinery company’s fault. The problem comes directly from how the project was originally planned.
The problem: poor material coordination.
Most projects treat windows and doors as abstract shapes on the plan. Designers draw ‘nice’ openings, visually proportioned, without considering how they are actually built.
For aluminum joinery, profiles usually come in bars of 6 meters, sometimes 7.5 meters.
This is where the issues start.
In Practice:
Every door, window, or sliding system is cut from these bars. If the dimensions are not optimized, it leads to:
material waste
unused leftover pieces
more joints than necessary
These losses don’t disappear—they are built into the final cost. This is perfectly normal, as the manufacturer cannot operate at a loss.
Easy Examples:
You need a fixed panel measuring 1730 × 1340 mm.
It seems like a standard choice in design.
The problem is that from a 6-meter bar:**
the required piece exceeds the bar length
the manufacturer is forced to use a new bar
You need a fixed panel measuring 1420 × 1300 mm.
The problem is that from a 6-meter bar:**
the total used from the bar will be about 5440 mm
the manufacturer will include the waste in the panel’s cost
The Classic Mistake:
The architect or client:
chooses dimensions ‘by eye’
does not consult the joinery supplier in advance
ignores the production process
The result is simple:
higher costs with no real benefit
sometimes even technical compromises later
What Standard Sizes Really Mean
There is no strict universal standard, but there are clear guidelines:
repetitive modules, such as 600 mm, 900 mm, 1200 mm
dimensions that divide efficiently into 6-meter bars
proportions that minimize material waste
It doesn’t mean making all windows identical. It means designing them intelligently.
Where the Cost Difference Comes In
At first glance, the differences may seem small. But across an entire house, with dozens of openings and complex systems, the losses add up.
The result can mean thousands of extra euros.
A Reality Often Overlooked
The cost of joinery is not just a price per square meter.
It reflects:**
the actual material used
inevitable waste
the complexity of execution
If the project is not optimized, the client pays for inefficiency. And that’s fair, because production follows the rules of the material, not the drawing.
How to Do It Correctly
For an efficient project:
Plan the joinery from the concept phase
Consult a specialist early
Use modular dimensions, not random ones
Avoid unnecessary variations between openings
Align the design with production
Conclusion
The difference between a well-drawn house and a well-thought-out one lies in details that aren’t obvious at first glance.
Openings for joinery are one of those details.
They are not just spaces for windows. They are points where design meets the reality of the material. Ignoring this can lead to higher costs without understanding why.
We hope you found this article informative and engaging.
Author: Eng. Robert M. Berzuc
Date: April 8, 2026
