Everything you need to know about timber sliding sash windows
Often, a sliding sash window needs replacing because it rattles, doesn’t protect against draught, is under-weighted
or the sashes are stuck. On many older properties, a sliding sash window has broken glass, rotted frames or a rotten
sill, they might be stuck or even painted shut and or have broken cords. Anyone of these issues individually or
combined are reason enough to look into buying new sliding sash windows for your heritage property.
But does
some of the terminology leave you scratching your head? Here’s what we mean:
Add weights / Make weights | small metal weights which help counterbalance a sliding sash. |
Back lining / Box lining | the timber outer lining on either side of the window between the stone surround and window frame. It gives additional draught protection and keeps dust out of the window frame. |
Bead | a strip of wood with a moulded, usually rounded face. Often used decoratively or to reinforce the meeting of two straight edges. Generally referred to as beading. |
Bottom rail | the rail that forms the bottom of the lower sash. |
Box / Case | the outer and inner lining, cheeks, box head and box lining combined form the sash box or sash case which is the framework that contains and supports the sashes. |
Box head | rests on top of the two cheek uprights, forming the upper surface of the window box. The top of the upper sash will rest against this when it’s closed. |
Box sash window / Sash window | a traditional timber frame window with movable sashes. Typically from Georgian, Victorian and Edwardian eras and can also be known as single or double hung sash windows depending on whether one or both sashes move. |
Cheek | the grooved vertical wooden sections either side of the window frame which stands between the sill and top of the sash window box. They provide the running surfaces for the sashes to slide against. You’ll find the cheeks have pulleys which the counterweighted sash cords pass through. |
Cord / Rope | a rope used to connect a sliding sash and a counterweight. Every sash will be connected to cords on both sides of the frame. Usually made from thick braided cotton, sash cords come in different gauges of thickness to suit the weight of the sash it needs to support. |
Cord plug | a metal ring used to hold the cord knot in place inside the sash box. |
Counterweight |
this metal weight counterbalances the weight of the sash holding it in position at any height. Sashes have
concealed counterweights on both sides in the cavity and are connected to the sash with the cords. They can
be made from steel, iron or lead, the latter being the choice when space is an issue. If a sash needs
rebalancing, add weights can be used to adjust the counterweight.
*An alternative to the traditional counterweight is a spiral balance. |
Drifting | if the sash isn’t counterbalanced correctly and doesn’t stay in place, it is said to be drifting. The sash might move at its own accord so it needs to be rebalanced. |
Drip groove | a channel cut into the underside of the exterior window sill to stop rainwater flowing back underneath the sill. If this happens rot or damage to the outside wall can occur. |
Exterior cill | a hardwood beam which acts as the lower surface of a sash window. On occasion this could be stone not timber but it is what the lower sash rests on when it’s shut. It will slope so rainwater runs off it and will include a drip groove. |
Fastner | the security lock that latches the bottom of the upper sash and top of the lower sash when they’re both closed. |
Glazing bar / Muntin | a strip of wood that divides the window either horizontally or vertically into smaller panes of glass; can also be known as sash bars. Georgian sash windows typically have six individual panes of glass separated by muntin bars. |
Horns | where the vertical stiles of a sash reach beyond the height of the sash frame, this extra bit is known as a horn. This can be ornately sculpted and provide extra strength to the frames. A lower sash would have the horns at the top and an upper sash would have the horns at the bottom. |
Inner cill | the wooden cill on the inside of the window. |
Inner and outer lining | timber side pieces that help form both the inside and outside box of the sash window frame. |
Lite | an individual pane of glass in a window frame, sometimes held by muntin bars. |
Lower sash | bottom sliding window frame of a sash window. The lower sash goes to the building interior. |
Meeting rail | the bottom horizontal rail of the upper sash and the top horizontal rail of the lower sash are known as the meeting rails as they meet in the middle of a closed sash window. |
Parting beads | the long wooden strips that sit in a grooved channel in the cheek and box head. They separate the lower and upper sashes so they can move easily. They can also be fitted into weatherpile carriers to reduce draughts. |
a removable cut out section in the cheek which allow access to the sash weights behind. A pocket cover conceals these. | |
Pulley | a roller which the weighted sash cord passes through as the sashes are opened and closed. Often metal or plastic. |
Rail | a horizontal wooden piece that forms the top and bottom parts of the sash frame. |
Rebalancing | overtime a sash can get heavy, causing it to become unbalanced and drift as its counterweights no longer hold it in place. When this happens the sash needs to be reweighted and rebalanced and the counterweights need to be readjusted. |
Re-cord | if a cord holding the sash breaks or deteriorates due to age it should be replaced and rebalanced. The sash cords should be replaced as a pair. |
Router (pronounced raow-ter) | a specialised carpentry power tool that cuts grooves or channels into wood. |
Routing | the term for using a router to cut a channel in a piece of wood to a precise size. |
Running surfaces | inner face of the sash box which the sashes make contact with. |
Sash | the sliding window frame made with timber rails and stiles, containing panes of glass. An outer wooden box holds the sash frame and a set of cord ropes, pulleys and counterweights support the heavy frame enabling it to move up and down. A sash window generally consists of a lower and upper sash, otherwise known as a sliding sash. |
Side rail / Stile | the structural timber section which forms one vertical side of a sash. |
Cill | the general term for the outer cill and inner cill. |
Spiral balance / Spring balance | the tube which contains a stainless steel rod and tension springs. This is an alternative to the traditional counterweight, cord and pulley arrangement and frees up space. |
Staff beads | moulded wooden strips that hold the lower sash in place, preventing it from falling into the room. If it’s fitted with a weatherpile carrier it helps reduce draughts. |
Top rail | the horizontal rail that forms the top of the upper sash. |
Upper sash | the top sliding window frame of a sash window. The upper sash sits on the outer side of the window. |
Weatherpile / Brush strip | a flexible fin or brush shaped strip. This seals gaps and keeps out draughts whilst allowing the sashes to move freely. |
Weatherpile carrier / Weatherstrip | a narrow and plastic grooved channel where a draught proofing weatherpile is placed. |
Weight cavity / Weight pocket | the concealed space on the sides of the window frame where the counterweights hang. |
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