Double Hung Window Systems - Which Type is Yours? Weight and Pulley vs Spiral Balance
Double Hung Window Systems — Which Type is Yours?
For a vertical sliding sash to stay in the open position, some form of counterbalance system is needed to offset the weight of the sash. Most double hung sash windows in Australia use one of two systems: the traditional Weight and Pulley System, or the more modern Spring / Spiral Balance System. Here's how to tell which one you have, and how to remove the bottom sash for each.
Why sash windows need a counterbalance
A vertical sliding sash is heavy — without something to offset that weight, it would simply drop under gravity the moment you let go of it. A counterbalance system takes care of this, holding the sash wherever you leave it, with little or no effort needed to lift or lower it.
Knowing which system your window uses matters if you're planning to install Ecobead parting bead — the bottom sash needs to come out to get access to the parting bead, and the way you release and refit it depends entirely on which counterbalance system is behind it.
The two systems compared
Weight & Pulley System
This is the more traditional system, relying on cast iron or lead weights to counterbalance the weight of the sash. The sash is attached to and suspended by lengths of sash cord. Each cord passes over a sash pulley fitted into the window jamb near the top of the opening, with the other end attached to the counterweight — housed in a pocket, or box, built into the side of the window.
When the window is correctly weighted, the sash requires little or no effort to operate and will remain open or closed as desired.
Removing the bottom sash
Untie the cord from the bottom sash to release it, then tie it off to hold it in place and stop it slipping back into the box. Once the Ecobead parting bead has been installed, untie the knot and tie the cord back onto the bottom sash.
Spring / Spiral Balance System
The counterbalance principle is similar to the weight and pulley system, but achieved differently. Spiral balances are made up of a spiral rod and spring housed inside a metal or plastic tube. The rod connects to the spring, which provides the tension that supports the sash. Each balance is held in place with a single screw at the top corner of the jamb, and one or two screws on the bottom sash — with two balances (one on each side) needed to properly support each sash.
Removing the bottom sash
Unscrew the spiral balance from the bottom sash. Take care here — the balance is under tension, so it may spin dramatically as the tension releases once unscrewed. Once the Ecobead parting bead has been installed, simply screw the spiral balance back onto the bottom sash.
Ready to install Ecobead?
Now that you know which counterbalance system you're working with, you're ready to remove the bottom sash and get started on installing your parting bead.
