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A double-hung window that feels unusually heavy, drops unexpectedly or refuses to stay open may have a problem with its balancing system. That does not automatically mean the whole window needs replacing. Where the sash and frame remain sound, repairing the operating hardware can help preserve the existing window—including the character of older timber joinery.
The important part is choosing the correct replacement. Similar-looking balances can have different lengths, weight capacities and fittings, so buying the closest match by appearance is not enough.
At Keeler Hardware, we help take the uncertainty out of the process. Our Window Sash Balance Finder is a guided search tool that asks a series of questions to help you identify the right balance. You will find it on our Window Sash Balances page—select Open Finder to get started.
Watch Our Sash Balance Measuring Video
Before ordering, watch our Keeler Hardware Spiral Sash Balance Product Finder video alongside this guide. Its chapters cover the measurements and window details used when selecting a replacement.
Pause at the relevant section, record your details and keep photographs of the existing hardware handy.
Use the video for measuring and selection guidance; follow the instructions for your exact replacement balance when it comes to installation and tensioning.
First, Identify Your Window’s Balancing System
The sash is the framed, glazed section that moves. Before measuring replacement hardware, establish how that section is supported.
Spiral sash balances
A spiral balance has an outer tube containing a spring mechanism, with a spiral rod and an attachment connecting it to the sash. Whitco’s spiral system, for example, uses a torsion spring and variable-pitch spiral for timber or aluminium double-hung windows.
Other spring balances
“Spring balance” is not always a precise description, because spiral balances also contain springs.
Other spring-operated systems use different mechanisms and fittings. Whitco’s Spring Sash Balance, for example, uses a tension spring and an adjustable friction foot. It is a different system from its spiral balance range, so identify the mechanism rather than relying on the word “spring”.
Traditional weight-and-cord systems
Traditional timber sash windows may use cords running over pulleys to counterweights concealed inside the frame. Broken cords or problems with the weights require a different repair from replacing a spiral balance.
For these windows, particularly heritage joinery, we recommend seeking advice before changing the original operating system.
How to Measure a Spiral Sash Balance Correctly
Start by photographing the complete assembly, its top fixing, the lower foot or shoe and any identifying numbers.
Do not disconnect a balance while relying on it—or the remaining balance—to support the sash. Support the sash independently and follow the appropriate procedure for controlling spring tension.
1. Measure the balance body accurately
Record the rigid body or tube length using the manufacturer’s specified measuring points. Do not confuse it with the length of the extended spiral or a measurement that includes the foot.
For example, Keeler’s Whitco No. 410 listing distinguishes between a 749 mm body length excluding the foot, a 775 mm closed length including the foot, and a 1,473 mm maximum extended length. The number “410” is a product size reference—not a length in millimetres.
“My balance measures 740 mm. Which one do I buy?”
First, confirm what you have measured. An approximate overall measurement is not enough to identify the correct replacement.
Our advice is to recheck the body length, note the brand and markings, and photograph both ends. Do not simply round 740 mm up to the nearest advertised size. Use our finder or ask the Keeler team to confirm the match before ordering.
2. Record the window and sash heights
Balance selection may also require the internal window-opening height, measured from the inside of the head to the sill, and the height of the upper sash, including any projecting sash horns.
Do not assume the top and bottom sashes need identical balance lengths. UNIQUE’s ordering guidance makes separate allowances for the upper sash and for sash horns. Follow the instructions for the system being selected.
Keep the measurements for each sash clearly labelled.
3. Identify the window material
Record whether the window is timber or metal, and photograph how the balance attaches.
It is worth recording the attachment details even when the existing balance looks familiar. Whitco, for example, offers standard-foot versions and versions prepared for an adjustable foot, with some components supplied separately.
4. Establish the complete sash weight
The relevant weight is the complete moving sash—including its frame and glass—not just the glass and not the entire window assembly.
For Whitco’s spiral system, select the published weight range using that complete sash weight. Do not divide it by two simply because two balances support the sash. Other systems may describe their ratings differently, so check the applicable selection guide.
A stronger balance is not automatically a better balance: the spring force must suit the sash. Excessive tension is not a substitute for correct selection.
Have an installer establish the weight when doing so requires disconnecting a heavy or difficult-to-access sash.
5. Measure the tube diameter and rebate
The rebate is the recessed groove that accommodates the balance. Measure its width and depth, as well as the outside diameter of the existing tube.
Tube diameter and rebate size are not the same measurement. For example, UNIQUE specifies an 11 × 11 mm rebate for its 10 mm balance and a 16 × 16 mm rebate for its 14.5 mm balance. Whitco recommends a 15 × 15 mm rebate for its spiral system.
Check the requirements for the exact replacement. A balance that matches the length but does not fit the groove is not a suitable replacement.
6. Check the feet, fittings and included accessories
Before placing your order, confirm whether the balance includes the required foot, fixing accessories and any tensioning tool. Do not assume everything shown in an illustration is included. Whitco’s adjustable-foot configuration, for example, requires the foot and accessory pack to be purchased separately.
Do Sash Balances Come in Pairs?
There are two separate questions: how many the window uses and how many the listing supplies.
A conventional two-balance arrangement uses one balance on each side of each moving sash. A double-hung window with two operating sashes therefore commonly has four balances in total.
However, used in pairs does not mean sold in pairs. Whitco lists individual balances in trade packs, so check the quantity supplied before ordering.
For a worn system, our recommendation is to replace the two balances supporting the affected sash as a matched pair, rather than pairing a new unit with another of uncertain condition. The other sash should be assessed separately.
Are There Left- and Right-Hand Versions?
Do not assume that components fitted on opposite sides need different part numbers.
Whitco’s spiral balance selection guide identifies the balance by size, weight range, foot option and finish rather than by separate left- and right-hand tube versions.
Nevertheless, check the entire assembly. Photograph the orientation of the feet and brackets, and record any left/right markings. Where a particular product specifies handing, follow that manufacturer’s convention rather than guessing which viewing direction it uses.
How to Replace Sash Balances: A Step-by-Step Overview
This is a general workflow for a like-for-like spiral balance replacement, not a universal fitting procedure. Attachment and tensioning methods vary between systems.
1. Confirm the replacement before dismantling
Use your measurements, photographs and the Window Sash Balance Finder to identify the replacement. Check the supplied components and read the fitting instructions before starting.
2. Support the sash and control the tension
Secure the sash independently. Follow the manufacturer’s release procedure and use the specified tool to control the loaded mechanism. Do not undo a loaded attachment and let the spiral spin freely.
3. Remove the old hardware and inspect the window
Remove the balance according to the window’s construction. Check the surrounding timber, joints and fixing locations. Deteriorated timber or paint-bound components need attention; replacing the balances alone will not resolve those defects.
4. Fit the replacements and required stops
Install the correct balances on the appropriate sash, following the specified fixing sequence. Ensure the feet engage properly and fit or reinstate the required stops.
5. Set the tension correctly
Use the specified winding direction and initial adjustment for that model. There is no universal turn count for every spiral balance. Adjust the paired balances equally and avoid overtensioning.
6. Test the operation carefully
Keep control of the sash while checking movement and support at intermediate positions. Confirm that it closes correctly and that the stops function. A sash that still drops or rises by itself needs further checking—not unlimited additional tension.
When to Call a Window Repair Specialist
We recommend professional assistance when the sash is large or heavy, the work is at height, or you cannot securely support the window and control the spring tension.
A specialist is also the sensible choice for damaged glazing, deteriorated timber, loose joints or a traditional cord-and-weight system requiring restoration. Assess the whole window rather than assuming every operating problem comes from the balance.
For heritage windows, seek advice before modifying the joinery or replacing the original operating system. Identifying the right hardware is only one part of a successful restoration.
Find the Right Sash Balance with Keeler Hardware
Successful sash window balance replacement starts with accurate identification—not choosing the closest-looking product.
Keeler Hardware’s range includes UNIQUE and Whitco sash balances, with different sizes and configurations for different applications.
Start with our Spiral Sash Balance Product Finder video, gather your measurements and photographs, then open the Window Sash Balance Finder on our website. The guided questions help you work towards the right replacement.
For an older or unfamiliar assembly, contact the Keeler Hardware team before ordering. Getting the balance type, dimensions, weight capacity and fittings right from the start is the foundation of a successful repair.
Call us on 1300 533 500, or contact us via chat or email.