Domakihub Secure uPVC Windows Fast: Install Sash Jammers Yourself
A simple screw-in upgrade that stops forced entry on sliding and tilt-and-turn uPVC frames.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
Sash jammers are one of the cheapest and most effective security upgrades you can make to a uPVC window or balcony door — and you can fit a pair in under ten minutes with a cordless drill. The video above walks through the full installation on a live frame; this guide pairs those visuals with step-by-step instructions and practical advice for Greek apartments, holiday rental villas, and hotel rooms where balcony access is a constant concern. Whether you are hardening your own home or protecting a property between guest stays, a sash jammer adds a second line of defence that most opportunist burglars will not bother to defeat.
Why uPVC Frames Are the Weak Point
Standard uPVC windows and patio doors rely on a single shoot-bolt or multi-point locking system built into the handle mechanism. A determined intruder can snap or bypass that handle with a screwdriver in seconds, especially on older frames where the plastic has fatigued or the mechanism has worn loose. Sliding doors and tilt-and-turn windows are particularly exposed because the locking points sit in the frame rather than the sash, leaving a gap that can be exploited with a lever.
Sash jammers work on a completely different principle: a rotating metal arm bolts directly into the inner face of the opening sash and, when flipped down, wedges hard against the fixed frame. Even if the handle lock fails, the jammer physically blocks the sash from moving. Fitting two — one near the top and one near the bottom — removes the ability to flex or bow the frame open, which is the technique burglars use when a single central lock is the only obstacle.
Choosing the Right Jammer for Greek Conditions
Most hardware shops in Greece and every major online retailer stock white or gold sash jammers sized for standard uPVC rebates. Look for a product made from reinforced zinc alloy or heavy-gauge steel rather than the thinner pressed-metal variants; the additional weight is negligible but the resistance to shear force is significantly higher. Check that the pivot arm is long enough to clear your frame profile — most Greek apartment windows use 70 mm or 76 mm system profiles, and standard jammers designed for those dimensions will fit without modification.
For holiday rentals and hotels, choose a model with a visible key-lock option so guests cannot accidentally leave the jammer engaged in the down position when the property needs to be ventilated through the window. Keyed jammers cost only a few euros more and prevent the common headache of a guest reporting a window stuck shut.
How to Fit a Sash Jammer: 5 Steps
- 1
Mark the position on the inner sash face
Close the window or door fully and, with the locking handle engaged, place the jammer body flat against the inner face of the moving sash, roughly 150 mm from the top corner. The pivot end should sit flush with the edge of the sash so that when the arm rotates down it lands squarely on the fixed frame rebate. Mark the two screw holes with a pencil; repeat the process 150 mm from the bottom corner for the second jammer.
- 2
Drill pilot holes through the uPVC skin
Use a 3 mm HSS bit at low speed to drill pilot holes at each pencil mark. uPVC is a soft material and a sharp bit will go through cleanly in one or two seconds — do not force it. Stop as soon as the bit passes through the outer skin; you do not need to penetrate the internal steel reinforcement inside the frame, and doing so unnecessarily can cause the screws to skip on the metal. If you feel significant resistance, reposition slightly to find a gap between the reinforcement bars.
- 3
Screw the jammer body to the sash
Align the jammer body over the pilot holes and drive in the supplied screws with a cross-head screwdriver or a low-torque drill setting. Tighten firmly but stop before the screw head bites into the plastic body — over-tightening strips the thread and loosens the fitting over time. Give the body a firm sideways tug once fitted; it should not rotate or shift at all. Repeat for both jammers on the same sash.
- 4
Test the pivot arm engagement
Flip the pivot arm down into the locked position. It should rest flat against the fixed frame or frame surround without any gap underneath the arm. If the arm clears the frame without touching, the jammer is positioned too far back on the sash — unscrew, reposition 3–5 mm toward the frame edge, and re-drill. If the arm binds before lying flat, it is too close to the edge; move it fractionally inward. A correctly seated arm should require deliberate upward finger pressure to disengage, not fall open on its own.
- 5
Confirm the sash cannot be forced with the jammers engaged
With both arms flipped down, try to push, pull, and flex the sash from the outside. On a correctly fitted pair of jammers the sash should feel completely rigid — no movement at all. If there is any give at the frame corners, check that the screw threads have not pulled loose in the uPVC; if they have, remove the screw, fill the hole with a small wooden plug or a screw anchor rated for plastic, and re-drive. Finally, make a note of the test date and check the screw tightness every six months, particularly on south-facing frames that experience the full Greek summer heat cycle.
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FAQ
- Will fitting sash jammers void the warranty on my uPVC windows?
- Drilling small pilot holes into the sash face for security hardware is generally accepted by uPVC manufacturers and does not affect weatherproofing or structural performance. However, if your frames are still under a manufacturer's guarantee, it is worth checking the warranty terms or asking your installer before drilling, as some warranties include exclusions for any field modifications.
- Can I use sash jammers on tilt-and-turn windows without stopping the tilt function?
- Yes — fit the jammer only on the side of the sash that faces the hinge when the window is in the turn (side-hung) position. When you want to tilt the window inward for ventilation, simply flip the arm up before engaging the tilt handle. The jammer has no effect on the tilt mechanism itself because the pivot point is on the opposite side of the frame from the tilt hinge.
- How many sash jammers do I need per window or balcony door?
- For a standard single-sash window, two jammers — one near the top edge and one near the bottom edge of the opening sash — give the best protection against both corner leverage and mid-sash bowing. For a wide balcony sliding door with a sash wider than about 900 mm, consider a third jammer at the midpoint of the sash height to eliminate any flex in the centre of the frame.