A sash window only stays up because something is pushing back against gravity on both sides of the sash. In an original window that's a cast iron weight on a cord. In a lot of newer double hung windows, and in plenty of retrofits, it's a spring balance instead. Get a cheap one and you'll be back inside the frame within a couple of years. Get the right one and you won't think about it again.
We get asked often enough about ordering balances that it's worth being straight about which ones we actually fit, and why.
The problem with a generic imported balance
Search "sash balance" online and you'll find plenty of unbranded options, usually sold by tube diameter alone with no real fitment guidance. The spring rate is a mystery, the rebate fit is approximate, and there's often no way to match the balance to the actual weight of your sash. Fit one that's underrated for the sash and it fails early, the window drops, and you're pulling the sash back out to do the job again. Fit a mismatched tube and it doesn't even sit in the groove properly.
It's the same false economy as a $2 tube of hardware-store filler on a rotten sill: cheaper today, more expensive the day it fails.
Why we only fit UNIQUE Sash Balances
We use UNIQUE Sash Balances, an Australian company based in Bayswater, Victoria with more than 30 years in sash hardware. They're not a generic reseller bundling in whatever's cheapest that quarter. Sash balances are the business, and the fitment chart behind our own calculator comes straight from their engineering, not a guess.
Every balance is specified to the window rather than sold as a one-size-fits-most part: the tube diameter matched to the rebate groove, the spring rated to the actual weight of the sash, and the top and bottom balances sized separately when the sashes aren't equal. That's the difference between a part that's rated for your window and one that's just rated for "a window."
The four balance types
| Type | Tube diameter | Rebate groove | Carries a sash up to |
|---|---|---|---|
| Type A | 10mm | 11mm x 11mm | 8.16kg |
| Type B | 13.4mm | 14 to 15mm | 14kg |
| Type D | 14.5mm | 16mm x 16mm | 13.6kg |
| Type HD | 13.4mm | 14 to 15mm | 18kg (heavy duty) |
Made to order for your exact window
Because each balance is built for one window rather than pulled off a generic shelf, they're made to order, which means a minimum lead time and no returns once an order's placed. That's exactly why we built a proper sizing tool instead of leaving people to guess: our sash balance calculator takes your window height, sash width, glazing and rebate size and gives you the balance type and product numbers for both sashes, ready to order, including the case where the top and bottom sashes are different sizes.
What this looks like in our own work
We didn't pick this part because it happened to be sitting in a supplier catalogue. It's what we fit across our own retrofit work Australia-wide, on the windows we stand behind with our own name. A balance has to hold a sash up every day for years without anyone thinking about it, so "cheap and generic" isn't actually cheap. It just moves the cost further down the track, to the day the sash starts dropping and the window has to come apart again to fix it properly.
Ordering a UNIQUE Sash Balance
All balance sizes are currently out of stock. You can still run your measurements through the sash balance calculator to get your exact type and product numbers, and send the spec through to join the waitlist for that size. We'll hold it and let you know the moment it's back.
If your window still has its original weight pockets, converting to balances usually isn't necessary at all: rebalancing with lead weights is simpler and the parts are in stock now. Balances are for windows built without weight pockets, or where the pockets have been lost. If your sash still runs on cords rather than a spring balance, our guide on replacing a broken sash cord and our sash cord buying guide cover that job instead.