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When it comes to traditional sash windows, the mechanism that supports the movement of the sashes is a crucial factor in their longevity, ease of use, and overall aesthetic. There are two primary systems: counterbalanced sash weights and spring mechanisms. While both serve the purpose of supporting the window’s operation, they differ significantly in performance, durability, and maintenance requirements.
At Traditional Sash Windows and Carpentry, we champion the timeless reliability of sash weights, but let’s explore the differences in detail so you can make an informed decision.
Sash weights are the traditional counterbalance system used in classic wooden box sash windows. This mechanism relies on:
Cast iron or lead weights, concealed within the window frame.
A cord and pulley system, where the weights move up and down in response to the sash’s movement.
Perfect balance, ensuring smooth, effortless operation without the need for modern tensioning devices.
This system has been used for centuries in Georgian, Victorian, and Edwardian windows and remains the gold standard for traditional sash window function.
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Spring-balanced sash windows use coil springs or spiral balances instead of weights. These are housed in slim plastic or metal tubes, which are fixed to the window jambs. Instead of a counterweight, the tension from the spring provides resistance, supporting the movement of the sash.
There are several types of spring mechanisms used, including:
Spiral Balances – A metal rod encased in a plastic tube with a spring inside, offering controlled movement.
Torsion Springs – A twisted metal coil that exerts force to counterbalance the sash.
Block & Tackle Springs – A more complex system combining pulleys and corded springs to provide smoother action.
While spring balances offer a slimmer profile, they come with certain disadvantages compared to the weight-based system.
Both sash weights and spring balances can be used with different types of sash openings, but their efficiency varies:
Only the bottom sash moves, while the top sash remains fixed.
Best suited to: Spring balances (but can also be made with weights).
Downside: Limits ventilation compared to a full sash window.
Both top and bottom sashes move, allowing for better airflow.
Best suited to: Traditional sash weights (better long-term performance).
Why? Spring-balanced versions can wear unevenly over time, leading to imbalance.
Allows the sashes to tilt inwards for easy cleaning.
Best suited to: Spring balances (due to their compact nature).
Downside: More moving parts = higher risk of mechanical failure.
Larger sash designs often used in bay windows or oriel-style projections.
Best suited to: Sash weights (supports heavier, wider sashes).
Why? Spring mechanisms often lack the strength to properly balance larger windows.
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Sash Weights: Can last 100+ years with minimal upkeep.
Spring Balances: Tend to fail within 10-20 years, requiring full replacement.
Sash Weights: Provides effortless movement, perfectly counterbalanced.
Spring Balances: Can become stiff or inconsistent over time.
Sash Weights: Ideal for heritage properties, maintaining authentic design.
Spring Balances: Often looks modern and less traditional.
Sash Weights: Simple to repair – replacing the cord restores function.
Spring Balances: More complex – springs degrade and require complete unit replacement.
Sash Weights: Silent operation, with no tensioning sounds.
Spring Balances: Can become creaky and loud over time.
Sash Weights: Suitable for all sash weights and materials, including heavy timber and double glazing.
Spring Balances: Limited weight capacity, often unsuitable for heavier double glazing.
At Traditional Sash Windows and Carpentry, we always recommend sash weights over springs for several reasons:
✅ Heritage Authenticity – Perfect for period properties, maintaining the original charm.
✅ Exceptional Durability – Many sash-weighted windows have lasted over a century with minimal upkeep.
✅ Simple Repairs – No need to replace the entire system – just a new cord or minor adjustment keeps it working.
✅ Smooth & Silent – No tension-based failures, noisy springs, or jerky movement.
✅ Ideal for Double Glazing – Can support the weight of modern double-glazed sashes without issue.
If you’re considering restoring, replacing, or upgrading your sash windows, it’s crucial to choose a mechanism that will stand the test of time.
If you have a heritage property or want long-lasting quality, sash weights are the best option.
If space is a constraint and you’re prioritising a compact design, spring balances might be a consideration—but be aware of their limitations.
At Traditional Sash Windows and Carpentry, we specialise in traditional sash windows with expert craftsmanship, high-quality materials, and proven longevity.
When it comes to selecting the best counterbalance system for your sash windows, the choice is clear. While spring balances may offer a more compact design, they simply can’t compete with the longevity, reliability, and smooth operation of traditional sash weights.Sash weights have stood the test of time for centuries, providing effortless functionality, minimal maintenance, and timeless aesthetics. Whether you're restoring a heritage property or upgrading to modern double glazing, a traditional weight-and-pulley system ensures superior performance and a more authentic look.
At Traditional Sash Windows and Carpentry, we specialise in expertly crafted, traditionally built sash windows that preserve the beauty and character of your home. If you’re considering a sash window upgrade or restoration, we’re here to help.
Last updated 2025-01-30