A window that refuses to stay open is one of those frustrating little problems that seems minor — until it drops on your hand or lets the rain in. The good news is that in most cases the fix is straightforward, and many homeowners can tackle it themselves with basic tools and a replacement part from a local hardware store.
Why Windows Fall Shut: The Most Common Causes
Before reaching for your tools, it helps to understand what's supposed to hold a window open in the first place. Most NZ homes use one of two systems:
- Friction stays – hinged metal arms (usually aluminium or stainless steel) that hold a casement or awning window open at a set angle through friction. Over time the friction mechanism wears out and the stay can no longer hold the window's weight.
- Casement operators (worm drives) – a geared handle-and-arm mechanism that winds the window open and holds it in position. These can strip internally or seize up.
- Sash balances – found in double-hung (vertical sliding) windows. Spring-loaded or weighted balances counteract the sash weight. When a balance fails, the sash drops.
- Louvre blades – louvre windows use a lever mechanism; if the blade clips or pivot pins are worn, blades won't hold their angle.
Tools and Materials You'll Need
- Flathead and Phillips screwdrivers
- Pliers
- Tape measure
- Replacement friction stay, sash balance, or casement operator (matched to your window size and weight)
- Light machine oil or a dry PTFE lubricant spray
- Safety glasses
Step-by-Step: Fixing a Friction Stay
Friction stays are the most common culprit in NZ homes, particularly in aluminium-joinery windows installed from the 1970s onwards.
1. Inspect the stay first
Open the window fully and look at the stay arms. Check whether the pivot screws are loose, the friction shoe (the sliding block on the track) is cracked, or the whole stay is bent. Sometimes a loose screw is all that's causing the problem.
2. Tighten or adjust before replacing
Using a screwdriver, tighten all screws on the stay and its track. Some friction stays have an adjustable friction nut — a small nut on the pivot point that you can tighten slightly with pliers to increase holding force. Try this before buying a replacement.
3. Replace the friction stay if needed
If the stay is worn beyond adjustment:
- Open the window and prop it safely with a piece of timber.
- Unscrew the stay from both the frame and the sash.
- Take the old stay to Bunnings or Mitre 10 to match the length (measured in millimetres when fully extended) and the fixing hole pattern.
- Fit the new stay in reverse order, ensuring all screws are snug but not over-tightened (which can crack aluminium frames).
- Test the window at several open positions before finishing.
Step-by-Step: Fixing a Double-Hung Sash Window
Older NZ villas and bungalows often have timber double-hung sashes with sash balances or traditional weights hidden in the wall cavity.
- Spring balances: These are replaceable. Unscrew the balance from the top of the sash channel, unhook the sash, and fit a new balance matched to the sash weight (usually stamped on the old balance or calculated by weighing the sash).
- Cord-and-weight systems: If the sash cord has snapped, you'll need to access the weight cavity via a small removable panel in the frame, re-thread new sash cord, and reattach the weight. This is fiddly but very DIY-friendly with a bit of patience — plenty of tutorial guides exist online.
Lubrication: A Simple First Step
Before replacing anything, try lubricating the stay or balance mechanism with a dry PTFE spray (avoid WD-40 on friction stays — it can reduce friction too much and attract dust). Sometimes a stay that seems worn is simply stiff and dirty, and a clean plus light lubrication restores function.
Checking for Underlying Frame Issues
If the window frame itself has racked (twisted out of square) due to foundation movement or timber shrinkage — common in older NZ homes — no amount of stay replacement will fully solve the problem. Signs include:
- The sash visibly sits crooked in the frame
- The window is hard to open or close as well as hard to keep open
- Gaps appear unevenly around the sash
Frame racking can be a symptom of structural movement, which warrants a closer look by a professional. The BRANZ website has useful guidance on building performance and weathertightness issues.
Does This Work Require a Building Consent?
Replacing a friction stay, sash balance, or casement operator on an existing window is routine maintenance and does not require a building consent under Schedule 1 of the Building Act. However, if you're replacing the entire window unit or altering the opening size, consent requirements may apply — always confirm with your local council. You can find general guidance at MBIE Building Performance.
When to Call a Professional
Call a qualified joiner or window specialist if:
- The window frame is racked, rotted, or structurally damaged
- You can't identify the stay or balance type and can't source a replacement
- The window is large, heavy (e.g. a big awning window), or at height where working safely is difficult
- The joinery is under a manufacturer's warranty that could be voided by DIY repairs
- You suspect weathertightness issues around the frame (a Licensed Building Practitioner should assess this — see LBP)
Safety note: Always prop a window securely before working on it. A falling sash or casement can cause serious hand and finger injuries. Wear safety glasses when working overhead.
A skilled local joiner can diagnose and fix most window problems quickly. You can find qualified joiners and window specialists in your area on tradedirectory.co.nz.
