BALANCING MODERN SASH WINDOWS
Modern double hung sash windows are balanced by a spring lift mechanism. These have a metal spiral rod inside a metal or plastic tube, fixed to the sides of the framework. The rod is attached to a spring inside the tube, tensioned to balance the weight of the window. The mechanism is easier to maintain than sash cords, though after a time the spring can lose its tension — in which case the window will not shut properly.
To cure this problem, unscrew the tube, and using the screw as a lever turn clockwise a few times to tighten the spring. If the spring has actually broken, you will have to remove the whole mechanism — it will be housed in the stile or the sash frame —and replace it. Spares are normally available from joinery suppliers which hold complete windows in stock.
To do this, remove the beading holding the sash in place and lift it from the frame.
Remove the mechanism from the frame. If it is housed in the stile, it will be secured by an Lbracket. Take it with you as a pattern when buying a replacement unit.
1. Put the new unit in position and raise the sash to its half height position.
2. Insert the screw through the tube and turn it to tension it, according to the maker’s instructions, in a clockwise direction.
3. Screw the back of the tube to the frame, replace the window and refit the beading in position. When the window is in the closed position, the tubes attached to the top sash are completely hidden, but the tubes attached to the bottom sash are visible.
These can be painted to match the window, but take care not to get paint on the springs.
The spring lift mechanism is housed in a groove down the side of the window. The tube contains a spring, tensioned by twisting it clockwise.