How to Choose a Sash Lock For a Double-Hung Window

 Double-hung windows are one of the most popular styles around, since they offer two operable sashes that slide up and down rather than just one, giving you more control over airflow and ventilation. They're also easier to clean than a lot of other window styles, as both sashes can usually tilt inward, which means you don't need to climb outside to wipe down the glass. On top of that, double-hung windows suit a wide range of home styles, from older character homes through to more modern builds, which is part of why they've remained so common over the years.

What Matters in a Sash Lock

source: mrwindows.com.au

Security

Security is usually the first thing people think about and for good reason, since a sash lock is often the only thing standing between your window and someone trying to force it open from outside. Look for sash locks for double hung windows with a solid latching mechanism, as flimsy hardware can be forced or jimmied without much effort. Some double hung window locks also include a keyed option, which adds an extra layer of protection beyond a simple flip latch.

Window Dimensions

The dimensions of your window matter quite a bit, since a sash lock needs to sit correctly where the two sashes meet in order to work as intended. A lock that's too small might not reach across the meeting rail properly, while one that's too large can look bulky and may not fit the available space at all. Measuring the meeting rail width and thickness before buying helps avoid a lot of hassle later on.

Window Weight

Heavier sashes, especially ones with thicker or double-glazed glass, put more strain on a lock over time, so the hardware needs to be sturdy enough to handle that load without wearing out quickly. A lock rated for lighter windows might work fine at first but can loosen or fail sooner when it's holding a heavier sash in place. This is why it pays to match the lock's rating to the actual weight of your windows rather than guessing.

Material

Sash locks typically come in materials such as brass, zinc alloy or stainless steel and each option offers a different balance of strength, appearance and resistance to corrosion. Brass tends to hold up well over time and gives a classic look, while stainless steel is a solid choice for coastal areas where salt air can cause other metals to corrode faster. Picking a material that suits your climate helps the lock last a lot longer.

Hardware Measurements

Getting the hardware measurements right is essential, since even a well-made lock won't function properly if the screw holes, backset or overall length don't line up with your existing window frame. It's worth measuring the old lock carefully before ordering a replacement, as sash lock sizes can vary between manufacturers and window styles. A mismatch here often means extra drilling or a lock that simply won't sit flush.

Types of Sash Locks

Brighton

The Brighton lock is one of the more traditional styles, featuring a curved cam that pulls the two sashes together tightly as it's turned, which helps reduce draughts and rattling. It's a common choice for a double hung sash lock on older or heritage-style homes, since its classic look suits timber frames particularly well. Brighton double hung window locks are generally easy to operate, though they don't usually include a keyed option.

Fitch

Fitch locks work in a similar way to Brighton locks, using a lever that rotates to draw the sashes together, but they tend to have a slightly more compact, low-profile design. This makes them a popular pick where space along the meeting rail is limited. Fitch locks are widely available and tend to be one of the more affordable sash locks for double hung windows.

Cam Lock

Cam locks use a rotating cam that hooks into a strike plate, pulling the sashes firmly shut as it turns, which gives a strong, secure hold once fully engaged. They're often found on newer windows, since many modern manufacturers fit them as standard hardware. Cam locks are generally straightforward to operate and offer decent resistance against someone trying to force the sashes apart.

Key-Operated

Key-operated locks add an extra layer of security by requiring a key to unlock the sash, rather than relying on a simple flip or turn mechanism. These are a good option for ground floor windows or homes in areas where break-ins are more of a concern. The trade-off is that they take a bit longer to operate, so they're not always ideal for windows used as an emergency exit.

Restrictors

Restrictors aren't a full lock on their own, but they work alongside a double hung sash lock to limit how far a window can open, which is especially useful in homes with young children or pets. They allow for ventilation while still preventing the sash from opening wide enough for someone to climb through. Many homeowners pair a restrictor with a keyed sash lock for a more complete security setup.