Staff Bead and Parting Bead: What They Do and When to Renew

The top sash rattles in a south-westerly. The bottom one has been painted shut for years and when you finally free it, it drops like a guillotine. Both of those faults usually come down to two strips of softwood that cost a few pounds a length and that nobody has looked at since the house was built.

They are the staff bead and the parting bead. Between them they hold the sashes in, keep the two sliding past each other without touching, and set the clearance that decides whether the window runs, sticks or rattles. Get them right and a hundred-year-old window works like a drawer. Get them wrong and no amount of new cord, new weights or new seals will fix it.

Where each bead sits and what it holds in

Stand inside the room and look at the window. The moulded strip running up each side and across the head, sitting proud of the frame and framing the bottom sash, is the staff bead. It is sometimes called the inner bead or the guard bead. It is pinned to the inner face of the pulley stile and the head lining, mitred at the top corners, and its only job is to stop the bottom sash falling into the room. Take the staff bead off and the bottom sash lifts straight out.

Now look at the vertical gap between the two sashes where they overlap. Set into a groove ploughed down the middle of the pulley stile is a plain flat strip, usually 7mm to 10mm thick and around 25mm deep. That is the parting bead. It separates the outer sash from the inner one so that they can pass without rubbing, and it stops the top sash tipping into the room. It is held by friction alone, in its groove. It is not nailed, it is not glued, and it is not meant to be.

There is a third piece nobody sees. Inside each side of the box, hanging from a nail at the top, is a thin lath called the wagtail or parting slip, which keeps the two weights in that box from clattering into each other as they pass. When you hear a dull knock inside the frame as the sash moves, the wagtail has usually dropped out or broken. Our glossary of sash window parts sets out the rest of the anatomy if you want the full picture.

Why the parting bead is the hardest-working timber in the window

The parting bead has three jobs at once, and they pull against each other.

It has to be thick enough to keep the sashes apart. On a typical London box sash the two sashes are separated by no more than the thickness of that bead, and the outer sash face runs within a millimetre or two of it. Wear the bead down, or fit a thin one where a thick one belongs, and the top sash gains sideways play. That play is the rattle. Wind pressure moves the sash across the gap and it knocks against the bead, twenty times a minute, all night.

It has to be thin enough to be pulled out. The only way to get the top sash out, and therefore the only way to renew a top cord, is to remove the parting bead first. It is a consumable, and it is designed to be levered out and pushed back in.

And it has to be stable. Bead is usually a straight-grained softwood, historically Baltic redwood, and it is a long thin section with almost no strength across its width. Left unpainted on the outer edge, it takes up moisture, swells, jams the top sash and then splits when someone forces it. Painted heavily on the inner face, it gets fatter and the sash binds.

That is why bead thickness is a diagnosis in itself. Feel the top sash: push it firmly towards the room and then towards the street. If it moves noticeably, the bead is worn or undersized. If you cannot move the sash at all and it takes real force to slide, the bead is either swollen or painted up.

Sections, profiles and why they vary house to house

There is no single national standard. What you find depends on when and where the window was made, and there is a good chance the beads in one room are a different section from the ones next door.

Staff bead profiles matter more than people expect, because they are the visible moulding in the room. Common ones are ovolo, lamb's tongue, torus and a plain splayed-and-rounded section. If you replace a staff bead with the nearest thing the merchant has, one window in the room will look subtly wrong forever. A joiner with a spindle moulder can run a matching profile from a sample; on a listed building, matching it is not optional.

Measure the groove rather than the old bead. Old parting bead is usually worn thinner than it started, so copying it perpetuates the rattle. A slip of card cut to fit the groove snugly gives you the width; the thickness you want is whatever leaves the top sash with a whisker of clearance, around 1mm to 2mm of total side play, no more.

Diagnosing which bead is at fault

Work through these in order. Most sash faults declare themselves in under a minute.

• Rattle, top sash only. Parting bead worn, or the wrong section fitted at some point. Occasionally the bead has shrunk and sits loose in its groove.
• Rattle, bottom sash only. Staff bead set too far off the sash face. It can often be prised, moved 2mm and re-pinned rather than replaced.
• Both sashes rattle, plus a howling draught. Both beads are tired and the window has probably never been draught-proofed. This is the standard case for draught proofing a sash window rather than for individual repairs.
• Bottom sash stiff, top sash fine. Staff bead swollen or painted against the sash. Run a knife down the joint, then check the bead is not cupped.
• Top sash stiff or immovable. Parting bead swollen, or painted into its groove from the outside. Very common on windows repainted from a ladder without opening them.
• Top sash tips into the room at the top. The parting bead has been lost or is short at the head. This wants doing straight away, because the sash is only being held by its cords.
• A bead that has gone soft when you press a bradawl into it. Wet rot, usually at the bottom 150mm where water sits on the cill. Renew the bead, but also look hard at the cill and the bottom of the pulley stile, because the rot rarely stops at the bead. There is more on that in our guide to wet rot in sash windows.

Taking the beads out without damaging anything

If you are doing this yourself, the order is not negotiable. Staff bead first, then the bottom sash, then the parting bead, then the top sash.

1. Cut the paint line. Run a sharp knife or a thin scraper down both edges of the staff bead, inside and outside, and across the mitres. Every layer of paint bridging that joint is glue.
2. Start the staff bead in the middle, not at the end. Slide a wide chisel or a bolster behind the long side piece halfway up and lever gently against a scrap of ply so you do not bruise the lining. The bead will bow away from the frame; work the gap outwards from the centre. Levering at a mitre snaps the mitre.
3. Pull the pins through from the back. Do not hammer them back out through the moulded face. Grip each pin with pincers and draw it through the bead. That keeps the face clean.
4. Mark the beads. Pencil on the back: "front bedroom, left, staff". They are not interchangeable, even within one window.
5. Take the bottom sash out. Lift it clear, hold the cords under tension, drive a nail through each cord knot into the pulley stile so the weight cannot run away down the box. Cut the cord if you are renewing it.
6. Now the parting bead. Cut the paint line on both faces. Grip it near the top with a pair of pincers or long-nose pliers and pull it straight out of the groove, working down its length. On a stubborn one, a proper parting bead tool, essentially a slim pry with a fork, saves a lot of splitting.
7. Free the top sash. It comes out the same way once the bead is gone.

Reassembly is the reverse, but do not paint the beads in place. Prime all four faces of every new bead, including the edge that disappears into the groove, before you fit it. That one detail is the difference between a bead that lasts thirty years and one that swells in the first wet winter.

When a bead should be renewed rather than refitted

Renew the parting bead if it is worn, split, soft, painted so thick that the section is no longer true, or the wrong thickness for the sash. Frankly, if the window is coming apart anyway, renew it regardless. It is a few pounds of timber and it is the single cheapest way to take play out of a top sash.

Keep the staff bead if you possibly can. It carries the original moulding, it is usually sound because it lives inside, and a bead that has been on a window for a century has settled into its position. Refit it, adjust it, ease it, but do not throw a good moulded bead away because it is easier to buy new.

Two situations force new beads even when the old ones are fine. The first is draught-proofing: standard parting bead at 7mm or 8mm is too thin to take a routed groove for a 4.8mm seal fin on both faces, so it gets swapped for a thicker grooved section or a bead supplied with the pile already fitted. Our article on brush seals and pile heights explains why that is sound practice rather than an upsell. The second is a change of glass. Fit heavier units and the sash sits differently against the beads, which is one of several knock-on effects covered in our piece on slimline double glazing.

The order of work that actually holds

Beads are the last thing to fit and the first thing to consider. If the window needs cords, the beads have to come off anyway, so do the whole job at once: cords, weights checked and matched, pulleys freed, beads renewed and set, and only then paint. Doing them separately means paying twice for the same dismantling.

And if the window is being painted, the beads should be finished off the window and refitted afterwards, or at the very least the sliding faces should be left with a thin, hard, fully cured coat rather than a thick soft one. The order of work for that is set out in our guide to painting sash windows.

What to do next

Open both sashes. If the top one moves at all, or if you can rock either sash sideways, take a torch and look at the beads before you spend money on anything else. A rattling window is very often a five-pound problem that has been quoted as a two-thousand-pound one.

If the beads are sound but the sash will not move, the fault is more likely paint, swelling or a broken cord, and our guide to a stuck sash window will get you further. If the beads are soft, split or missing, or if you would rather not lever century-old joinery apart on a Saturday, our sash window repair service covers London and this is bread-and-butter work: half a day for a typical window, beads renewed and the sashes properly balanced afterwards. If several windows in the house rattle and howl, it is usually more economical to have them draught proofed as a set, because the beads get renewed as part of that work anyway.