Do all sash windows have weights? — A closer look at sash window options

What are sash window weights?

Before the invention of spiral balance sash windows (more on this later), sash windows operated using a system of cords, pulleys, and counterweights to adjust the windows’ aperture, from fully closed to fully open, and anywhere in between. Sash window weights were typically made from lead or cast iron, and later steel, cast into either a round or square tube and featuring a loop to connect to the cable or cord at the top.

Connected to the bottom sash, the weights would counterbalance the sash as it was lifted open. This style of sash window, also referred to as the ‘box sash window’, remained the norm during the Georgian, Victorian, and Edwardian eras.

Do all sash windows use weights?

Patented in the 1930s, the spiral balance sash window, or spring balance window, dropped the counterweight balance system for a spring-based system and quickly gained popularity. This new system was more compact, making it better suited for small apartments or windows with limited installation space.

You can imagine a spiral or spring counterbalance as a tightly wound spring inside a tube. One end of the spring is attached to the side of the window sash, and the other end connects to a fixed point inside the frame. As you open the window, the spring pulls tight and becomes a store of elastic potential energy, counterbalancing the weight of the sash. This makes the window feel lighter—the ‘pop’—and also allows it to stay in place when you let go, assuming that the mechanism is in good working order.

How to tell if your sash windows use weights or a spiral?

The easiest way to tell if your windows have weights or not, short of opening the frame and manually checking, is to gently lift the window, applying a constant force from completely closed to completely open. If the weight of the sash feels consistent and the movement is smooth, you likely have a box sash window. If the window seems to resist at first, then gradually feels lighter as you lift it, it’s probably a spiral sash window.

It’s important to note that while box sash window casings are typically slightly bulkier than spiral sash windows, the difference isn’t always obvious unless you’re looking for it.

Box or spiral sash windows? Your choice at Ayrton Bespoke

Ayrton Bespoke is a leading London supplier of bespoke timber windows and front doors. We design and manufacture bespoke windows tailored to our clients’ needs, offering both box sash windows—either as custom designs or like-for-like replicas in Conservation areas and period homes—and spiral sash windows, which are ideal for tight spaces such as dormers or bathrooms.

Whether you’re looking for smoothly operating box sash windows for a new home, perfect replicas of your existing cord-and-weight sash windows for a renovation project, or beautiful and bespoke timber sash windows for a tight spot, Ayrton Bespoke has you covered.

Reach out to our team today for an obligation-free discussion of how we can bring your vision to life with expertly crafted, made-to-measure sash windows.