Your double hung window used to stay wherever you left it. Now you’re propping it open with a paint tin, or it drops the moment you let go — which is a genuine problem if it’s ever your fingers, or your child’s, underneath it when it falls. Here’s what’s actually failed inside the window, and why it isn’t something you can just tighten or spray with WD-40.
Why won’t my double hung window stay open?
A double hung window that won’t stay open, feels heavy, or slams shut usually has a worn or broken spring or spiral balance — the mechanism inside the frame that counterbalances the sash weight. Once these wear out, the sash can no longer hold its position at any height, and the balance needs replacing rather than the whole window.
Every double hung sash is heavier than it looks, and it relies entirely on a hidden mechanism in the frame to offset that weight. When that mechanism is working, lifting the sash feels almost effortless, and it stays exactly where you leave it. When it’s worn out, none of that holds — the window either won’t budge, or it moves and then drops the moment you stop supporting it.
Spring balances vs spiral balances: what’s actually inside your window
There are two common versions of this mechanism, and which one you have affects how the fault shows up. A spring balance uses a coiled spring under tension inside a tube in the frame channel. A spiral balance uses a twisted metal rod inside a tube, with a spring-loaded tensioner at one end.
Both do the same job — they just wear out slightly differently. A spring balance tends to fail suddenly, snapping or losing tension all at once, so the sash goes from fine to completely unsupported. A spiral balance tends to weaken gradually, so you’ll often notice the window getting harder to hold before it stops holding altogether.
You can get a rough read on which one you have without removing anything: look into the channel at the side of the sash. A coiled spring visible through a slot points to a spring balance; a straight tube with no visible coil usually means a spiral balance inside.
What is a window spiral balance?
A spiral balance is a sealed tube containing a twisted metal rod under tension, fitted into the side channel of a double hung window frame. As the sash moves up and down, the rod twists and untwists, creating enough resistance to hold the sash at any height without you needing to prop or latch it.
The safety risk of a window that won’t stay up
This isn’t just an annoyance. A sash that drops without warning is a real risk to fingers and hands, particularly for young kids who don’t yet know to keep clear of a window they’re leaning on. It’s also a security gap, since a window that won’t stay open on its own often gets propped with whatever’s on hand, which usually isn’t something that holds firmly if someone pushes on it from outside.
There’s a compliance angle too, particularly in strata buildings and rental properties across NSW, where windows above a certain height are required to have a working safety device that limits how far they can open. A failed balance doesn’t remove that requirement — if anything, it makes it more important that the window’s hardware is actually functioning as intended.
Why does my window keep falling down?
A window that keeps falling almost always has a balance that’s lost its tension entirely, rather than one that’s just stiff or slow. Once a spring snaps or a spiral rod loses its twist, there’s nothing left inside the mechanism to counteract the sash’s weight, so gravity takes over completely and the sash drops as soon as it’s released.
Can you replace a balance yourself, or is this a call-a-pro job?
Balances are a genuine parts-and-labour repair, not a lubrication fix — no amount of spray oil restores tension to a spring that’s lost it. Replacing one involves removing the sash, extracting the old balance from its channel, and fitting a new one matched to the exact weight and height of that specific window, which varies more than most people expect across older and non-standard sashes.
It’s technically a DIY-possible job for someone comfortable removing a sash and working with a loaded spring under tension, which is exactly where it goes wrong for a lot of people, since a spring balance under load can spring back forcefully if you’re not expecting it. Matching the correct replacement part for an older or aluminium-framed double hung window adds another layer that most hardware stores can’t help with.
Balance gone? Book a free assessment, and we’ll have it fixed, usually in one visit.
Can a double hung window be repaired?
Yes — a double hung window with a failed balance is one of the more straightforward window repairs, provided the frame and sash themselves are still in good condition. It’s the balance mechanism that’s failed, not the window, and replacing it restores full function without needing to replace anything else.
What a spring and spiral balance replacement involves
A proper repair starts with identifying which type of balance is fitted and matching a replacement to the sash’s actual weight — too light and the sash won’t stay up, too heavy and it won’t come down easily. The sash comes out, the worn balance is removed from the channel, and the new one goes in and is tensioned correctly before the sash is refitted and tested through its full range.
Done properly, it’s a same-visit job with our spring and spiral balance replacement service, and it’s the fix for this exact fault — not a full window replacement, which almost nobody actually needs for a worn balance.
How do you fix a window that won’t stay open?
The fix is to replace the worn spring or spiral balance mechanism inside the frame, matched to the correct weight for that specific sash, rather than attempting to adjust, lubricate or tension the existing one — a balance that’s lost its tension can’t be restored, only replaced.
A window that won’t stay up on its own isn’t a fault you need to live with or work around. Once you know it’s the balance and not the window itself, it’s a same-visit fix, and one less thing propped open with whatever’s within reach.
Book your free assessment today and get your double hung windows staying exactly where you leave them again.
This guide is prepared by Lock & Roll’s licensed window and door technicians (Master Lic. 000104324). Individual cases vary — the guidance above is general and not a substitute for an on-site assessment.
