How to repair a sash window like a pro

With a step-by-step guide.
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Repair your period sash window like a pro and it will last another century!

Old houses come with lots of beautiful features… but they also come with lots of problems, too.

Adam’s helping out Jess, whose home has 100-year-old sash windows that are in really bad shape. Not only are the sashes broken, but some of the glass panes are too, and getting these windows fixed professionally isn’t cheap!

Luckily, with the right tools and some know-how, this is a job you can easily do yourself. 

Step-by-step guide to sash window repair

Federation sash windows are a stunning architectural feature of your period home. (Credit: Getty)

Gather your supplies

  • Contact paper
  • 3mm glass pane (cut to order)
  • Framing pins
  • Putty
  • 8mm x 15m sash cord
  • 30mm screws
  • 40mm bullet nails

You will also need 

Step 1

(Credit: Sue Ferris/

Cut paint in groove between stop bead and surrounding frame with utility knife. Prise stop bead away from frame with scraper or chisel. 

Step 2

(Credit: Sue Ferris/

Bend bead in middle to remove it from mitred cut at top and bottom. Use pincers to remove old nails from sash and back of stop bead. Identical beading is available to buy from your timber supplier.

Step 3

(Credit: Sue Ferris/

Remove stop bead from other side. Remove lower sash window. If cord is still attached, cut cord while you support the weight.

Step 4

(Credit: Sue Ferris/

Score paint around pocket covers and parting bead with utility knife. Use scraper and chisel to loosen, then pry off parting bead that separates upper and lower sash windows.

Step 5

If pocket cover is jammed, drill a small screw halfway into cover. Use pliers to pull screw and remove pocket cover.

Step 6

(Credit: Sue Ferris/

Remove weights from inside pockets with remains of cord attached. Note which weight goes with which sash. Remove old cord from weights. Remove old cord and nails attached to sash sides with pincers.

Step 7

Lay window on workbench. Wearing eye protection and gloves, tape up glass with contact paper to contain glass fragments. With a scraper and chisel, remove old putty.

Step 8

Use pincers to remove any old nails around glass. Use scraper to cut paint away from underside of window. Carefully remove and dispose of glass.

Step 9

Clean up sash frame with scraper and chisel. Brush away debris.

Step 10

Measure new window pane at width and length of internal frame. Check internal distances at each end, then with lowest measurements, take 5mm away from width and length to allow a small gap around the glass. 

Step 11

Insert new glass pane into bottom window slot, then lower into frame. Use framing pins to hold glass to frame, push in place with back of chisel.

Step 12

Apply putty around frame with scraper, then smooth out.

Step 13

(Credit: Sue Ferris/

Oil pulley with WD40. Tie a screw to a piece of lightweight string, then tie other end of string to new cord. Feed screw through top of pulley, then down. Pull cord through pocket. Cut cord at about 1.5 times window height. Repeat on other side.

Step 14

To replace cord or glass on upper sash, repeat Steps 4-13 as required Reinstall parting bead once upper sash work is complete.

Step 15

(Credit: Sue Ferris/

Remove screw and string from hanging cord, then secure to weight with a figure 8 knot. Reinsert weight into pocket, then insert and push pocket covers into place. Repeat on other side.

Step 16

(Credit: Sue Ferris/

Pull cord to raise weight to the top of frame. Stand sash upright on sill, then insert cord into grooves. Insert 6 screws through cord, then screw tight into sash. Insert top screw 200mm from top of window.

Step 17

Check sash moves. Reattach stop beads with bullet nails. Fill nail holes and gaps with wood filler.

Step 18

Allow putty to cure for 6 weeks before painting. Scrape, sand and touch up with primer, then paint frame and sash.

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