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The thin strip of timber that lets both sashes of a box sash window slide past each other independently — and why it's one of the first things removed for a proper repair.
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The thin timber strip hidden inside every box sash window frame — what it does, what goes wrong, and when it needs replacing.
Window sticking, rattling, or won't stay up? This is often a parting bead problem — see our sash window stuck guide for the other common causes.
Open up the side of a traditional box sash window and, hidden between the two sashes, you'll find a thin strip of timber running the full height of the frame. This is the parting bead — a small, unglamorous component that does an important job: keeping both sashes running smoothly in their own separate channels. It's also one of the first things a joiner removes when working on your window, which is exactly how it's meant to be used.
A parting bead is a thin timber strip set into a groove running down the middle of the pulley stile — the vertical side member of the box frame. It sits between the outer (upper) sash and the inner (lower) sash, physically separating the two channels they slide in. Without it, both sashes would share the same open groove and could swing sideways, rub against each other, or jam.
The parting bead works alongside the staff bead — the innermost strip on the room side, which retains the lower sash against the frame. Together, these two beads (plus the meeting rail where the sashes overlap) are what make the whole weight-and-pulley sliding mechanism possible.
Both sashes share the same box frame opening, sliding vertically past one another so the window can open from the top, the bottom, or both. Without something separating their channels, the two sashes would occupy the same space and interfere with each other every time the window was opened. The parting bead solves this simply: it splits the frame into two independent tracks, so the outer sash and inner sash can pass each other smoothly without touching.
Unlike most of the frame, a parting bead is traditionally fitted so it can be taken out again — not glued or permanently fixed. This is deliberate: to reach the weight compartment for a sash cord repair, or to lift the upper sash out for painting or draught-proofing, a joiner needs to slide the parting bead free first. A well-fitted original sash window is designed to be serviced this way for its entire working life, which is often well over a century.
The most common issue on London period properties. Successive coats of paint bridge the gap between the sash and the parting bead, bonding the two together until the sash won't move at all. This needs to be carefully scored and freed rather than forced.
If a window has been forced open awkwardly, or the bead was replaced with one of the wrong thickness, it can bow inward and create a pinch point. The sash then binds tightly on that one side throughout its travel, even though nothing else is wrong.
Over decades, a parting bead can shrink, split, or simply go missing during a previous repair. The gap it leaves lets the sash rattle in the wind and draughts pass straight through — a common finding on unrestored Victorian and Edwardian sashes.
Parting beads come out most often as part of other work: withdrawing a sash for sash cord replacement, fitting brush seals during draught-proofing, or freeing a stuck sash window. If the old bead is split, warped, or the wrong size for a smooth fit, we replace it rather than reuse it — reusing a damaged bead is a false economy that just brings the customer back with the same problem.
Getting the fit right matters more than it looks. A new bead cut slightly too thick will bind the sash and make it feel stiff; cut too thin, and the sash will rattle exactly as it did before. We machine each replacement to match the original clearance for that specific window, and where a window is being draught-proofed at the same time, the brush seal is routed into the new bead as part of the same job.
Parting bead and staff bead replacement typically starts from £100 per sash, and is usually carried out alongside cord replacement, draught-proofing, or a full sash window restoration rather than as a standalone job.
A parting bead is a thin timber strip set into a groove in the pulley stile of a box sash window. It sits between the outer (upper) and inner (lower) sash, keeping each one running in its own separate channel so they can slide past each other without rubbing or jamming.
Repeated coats of paint applied over the years can bridge the gap between the sash and the parting bead, bonding the two together. The fix is to score carefully through the paint film along the joint rather than forcing the sash, which can split the timber or crack the glass.
Parting bead and staff bead replacement typically starts from £100 per sash. It's usually carried out alongside sash cord replacement, draught-proofing, or a full restoration rather than as a standalone job. We can confirm exact pricing during a free site survey.
Yes. The parting bead, along with the staff bead, is carefully slid out to release the sash so it can be withdrawn from the frame and the weight compartment accessed. Both beads are designed to be removable for exactly this kind of maintenance.
It's often a parting bead or staff bead issue — get in touch for honest advice and a free, no-obligation quote.
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