Sas How to Repair a Window Sash
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How to Repair a Window Sash

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Window sash built in the 18th and 19th century were assembled with mortise and tenon joints using wooden peg to hold the joints tight. The beauty of this construction is that it can be taken apart, repaired and put back together with simple hand tools. The three most common repairs are the glazing bars on the exterior, muntins and rot typically on the bottom rail against the sill and the upper sash meeting rail.

Glazing Bar Repair
Glazing bars on antique sash are frequently damaged due to weathering or rot when the sash have not been kept painted and glazed. These are easily repaired.

Dissassembling a Sash
A sash can be dissassembled by removing the wood peg(s) on the components you want to work on. There is a peg on each mortise and tenon joint which can be removed with a pin punch and hammer. Frequently one side of the peg is larger than the other so you will want to drive the peg out from the smaller end so as not to damage the sash.

Once the peg(s) are removed, use a mallet or soft faced hammer to separate the rail and stile. This will prevent damage to the profile of the sash. You can now examine the joints and see if any repairs are needed. Once the rail and stiles are moved apart, the muntins will be easily removed or fall out without assist.

Replacing Muntins
Muntin are the vertical and horizontal pieces of wood that separate the panes of glass. The front has the molded contour seen from the interior. The back of the muntin is used to support the glass and glazing.

Replacing Pegs
Sash pegs or pins get loose over time from expansion and contraction due to moisture. This can distort the pegs to the point where the joints are quite loose. At this point the old pins should be replaced or some addtional repairs may be needed to repair the joints.