Introduction
Old timber sashes look great, but the rattles and cold streaks drive clients mad. You know the story: gaps, paint build‑up, sticky cords, then call‑backs when the wind picks up. This guide breaks down a proven draught‑proofing system for box sashes—what it is, why it works, how to fit it properly, and where contractors commonly lose time. We’ll cover practical specs, production rates, and a clean way to capture the scope on site and turn it into a signed proposal quickly.
Table of Contents
Key Takeaways
- Many contractors find that a proper brush‑seal system eliminates rattles and noticeably reduces draught complaints, especially on windy gables.
- Common pile sizes are 5–8 mm; matching pile height to real gap sizes is the difference between smooth travel and stuck sashes.
- A two‑person team commonly completes 4–6 sashes (two windows) per day when frames are sound and repairs are minimal.
- Using on‑site voice, text, and photos to capture each window’s condition reduces rework and speeds proposals; it often cuts admin by hours per week.
Why Sash Windows Leak Air
Many period sashes have cumulative wear: shrunken timber, painted‑over tracks, distorted meeting rails, and loose beads. Add 1–2 mm of clearance per side across the full perimeter and, in general, the equivalent open area adds up fast—clients feel that as cold streaks and whistle noise.
The Problem You’re Solving
- Gaps at the meeting rails and staff bead create continuous leakage paths.
- Hardened paint and misaligned latches stop the meeting rails from compressing.
- Loose pulleys or stretched cords tilt sashes, opening gaps top or bottom.
Why Traditional Fixes Fall Short
- Heavy caulk lines and paint “seals” look fine in summer, then shear off by winter.
- Foam strips crush unevenly and often snag; many don’t survive a repaint.
The Draught‑Proofing System
A modern retrofit uses discrete brush (pile) carriers in beads and rails so the sash still slides freely but seals when closed.
Components That Matter
- Staff bead with integrated pile carrier (commonly 5–6 mm pile).
- Parting bead with pile or twin‑pile carrier for the channels.
- Meeting rail carrier with low‑profile pile (often 4.8–5 mm).
- Top head seal (pile or compressible strip) for the upper sash.
- Bottom rail carrier for the cill seal (helps stop wind‑driven ingress).
Practical Specs
- Typical router cutter: 3–4 mm; groove depth 8–10 mm to seat the carrier firmly.
- Pile options: 4.8, 5, 6, 8 mm are common; choose by measured play, not guesswork.
- Fixings: pins or small brads; many fitters use 25–30 mm brads for beads.
What Success Looks Like
- Sashes glide but don’t rattle when slammed or in gusts.
- Latch closes with modest pressure; no meeting‑rail daylight.
- Even compression along both stiles; cords track smoothly.
How It Works On Site
Step 1: Survey And Measure Gaps
- Remove staff bead section to check play and cord condition.
- Measure travel clearance at multiple points; aim for less than 2 mm variance per side after works.
- Note repairs: softwood splices, pulley screws, loose weight knots. Many contractors find that pulling in a new cord or two saves more time than fighting a tilted sash all day.
On‑Site Capture That Saves Time
Talk through each window while you’re in the room: “Front lounge, bay, 3 sashes; top sash sticks; cords frayed; 6 mm pile at parting bead; 5 mm at meeting rail; minor sill splice.” Add photos of the meeting rails and pulley stiles. In Donizo, the voice‑to‑proposal flow turns this into a structured scope and a professional PDF you can send before you leave the street. Clients can sign digitally with legally binding e‑signature, and accepted proposals convert to invoices in one click.
Step 2: Strip, Clean, And Square Up
- Remove staff bead fully and the lower sash; lift the parting bead to free the upper sash.
- Scrape paint ridges in channels; check pulleys are square and solid.
- Sand mating surfaces; don’t remove historic profiles beyond what’s needed for a consistent track.
Step 3: Route And Fit Carriers
- Rout grooves for meeting rail and bottom rail carriers (8–10 mm deep). Keep the cutter centred; a wandering groove is the fastest route to a stuck sash.
- Install parting/ staff beads with the correct pile. Start long; trim only after test fit.
- Fit the head seal channel and test the upper sash for smooth travel.
Step 4: Balance And Re‑Cord As Needed
- If a sash creeps down, adjust weights; many period windows have mismatched or paint‑bound weights.
- Replace cords where frayed; a clean pulley and fresh cord can feel like a new window.
Step 5: Test, Adjust, Finish
- Close sashes, latch, and check even contact. You’re aiming for a snug close that doesn’t require forcing the latch.
- Pin beads carefully; bury brads and fill for a clean paint line.
- Final run: sashes should travel without snagging the pile.
Real Results And What Clients Notice
Many contractors report that the combination of bead carriers plus a head and cill seal:
- Stops rattles completely in everyday wind.
- Cuts draught complaints noticeably—especially in rooms with exposed elevations.
- Reduces dust ingress and street‑noise transmission to a degree clients can hear.
Production And Timeframes
- In general, a two‑person team completes 4–6 sashes per day when frames are sound and only light cord work is needed.
- Add time for timber repairs or seized pulleys; complex bays can add an extra hour or two.
Example: Semi‑Detached, London Brick, Front Elevation
Problem: Two street‑facing windows rattled, meeting rails gapped at the centre, and one upper sash wouldn’t stay up.
Solution: New cords, bead carriers with 6 mm pile on channels, 5 mm at meeting rails, head seal, and a bottom‑rail carrier.
Outcome: Client reported immediate stop to rattles and a much calmer room on windy nights. The team completed both windows (four sashes) in a day, including re‑cording and latch alignment.
Pricing, Specs, And Common Mistakes
Pricing Factors You Can Explain Clearly
- Access: bays, shutters, or heavy curtains add time.
- Repairs: splices, new cords, pulleys, weight adjustments.
- Finish: making good and paint touch‑ins.
- Extras: security restrictors, refurbished latches, discreet stops.
Using Donizo, you can capture these as line items by voice (“re‑cord upper sash”, “pulley fix left”, “sash restrictors x2”). Clients see exactly what they’re paying for, and with e‑signature they can approve on the spot. Once accepted, convert to invoice and track payments without retyping.
Specs That Keep You Out Of Trouble
- Match pile height to measured play: too short and you’ll leak; too tall and the sash binds.
- Keep grooves straight and consistent: 8–10 mm depth is typical—shallow grooves let carriers ride out.
- Aim for even compression: the latch should close with firm finger pressure, not body weight.
Common Mistakes (And Fixes)
- Over‑routing thin meeting rails: use a depth stop; if in doubt, use a low‑profile carrier.
- Stuck sashes after installation: downsize pile by 1 mm or ease paint ridges in the channel.
Compliance And Heritage Notes
- Listed buildings: draught‑proofing is often treated as maintenance, but always confirm with the local authority/ conservation officer before altering original fabric.
- Lead paint: assume pre‑1960s coatings may contain lead; use safe removal methods and PPE.
Frequently Asked Questions
Do I Need To Remove The Sashes To Draught‑Proof Them?
You’ll remove at least the lower sash to do the job properly and usually lift the parting bead to free the upper sash. Working only from the room side without removal often leaves paint ridges and misalignments that defeat the seals.
Will Draught‑Proofing Stop Rattles Completely?
In general, yes—when the bead carriers and meeting‑rail seal are correctly sized and the sash is balanced. If you still hear a rattle, check uneven compression at the meeting rail or loose staff bead fixings.
How Long Do The Brush Seals Last?
Contractors commonly see quality pile and carriers holding up for many years under normal use. Expect periodic repainting and the odd cord replacement as routine maintenance.
Can I Use This On Slightly Warped Sashes?
Mild bowing can be accommodated by choosing the right pile height and ensuring even compression. Severe warping may need timber splices or straightening before seals will work properly.
Do I Need Permission For Listed Homes?
Often, draught‑proofing is viewed as a reversible maintenance upgrade, but policies vary. Always check with the local authority or conservation officer before you rout or alter historic profiles.
Conclusion
Draught‑proofing sash windows isn’t a gimmick—it’s a tidy, durable upgrade when you choose the right pile heights, keep grooves straight, and balance the sashes. Survey well, fix the fundamentals (cords, pulleys, latches), then fit the carriers and seals. To speed the business end, capture the scope on site with voice, text, and photos in Donizo, send a branded PDF, get a legally binding e‑signature, and convert the accepted proposal to an invoice in one click. Less admin, warmer rooms, happier clients.
