Glazing / Flat Packers

Glazing packers do a quiet job. Nobody admires them once the unit is in and the beads are snapped home, but if they’re wrong or missing, everybody notices about six months later. These glazing / flat packers are 28mm x 100mm plastic strips, colour coded by thickness so you can grab the right one without squinting at a tape measure.

The range runs from 1mm up to 6mm. Green is 1mm, black 2mm, white 3mm, grey 4mm, blue 5mm and red 6mm. Most fitters learn the colours within a week and then wonder how they ever managed without them. You can buy single thicknesses in packs of 100, 300 or 1000, or go for the mixed pack of 100 or the mixed tub of 300 if you want a bit of everything in the van.

What Glazing / Flat Packers Are Actually For

A sealed unit should never sit directly on the frame rebate. Packers carry the weight of the glass, hold the unit central in the opening and keep it square. Setting blocks go under the glass at the bottom edge, and these flat packers fill the gaps around the perimeter and help you take up the difference between the unit and the rebate. Get the packing right and the sashes open and close cleanly. Get it wrong and you’ll be back on site wondering why a casement is dropping.

They’re also handy outside of glazing. A 28x100mm flat packer is a useful size for levelling window and door frames, packing out behind fixings, and generally taking up small gaps where a hardwood wedge would be too crude. Plastic doesn’t rot, doesn’t swell and doesn’t go soft if it sits in a damp opening, which is more than you can say for the offcuts of timber some sites still rely on.

Choosing the Right Thickness

The thickness you need depends on the gap between the glass and the rebate. Dry glaze the unit first, check the clearance all round, then build up with the colours to suit. Combining packers is perfectly normal. A white and a green gives you 4mm, for example, and it’s often easier to stack two thin ones than carry every thickness in bulk. If you’re doing a full day of mixed jobs, the mixed pack or tub saves you buying six separate bags and losing half of them under the seat.

The material is a rigid plastic that holds its shape under load, so the glass stays where you put it. The packers won’t compress over time the way softer materials can, which matters on larger or heavier units where the weight is significant.

Buying Glazing Packers in Bulk

If you’re glazing regularly, the 1000 piece packs make sense. They work out noticeably cheaper per piece, and a pack of the common thicknesses will last a long time on domestic replacement work. Smaller firms and one-man bands often prefer the mixed tub, as it keeps everything in one place and the lid stops them scattering across the van floor, which is where packers usually go to disappear.

Every thickness is held as its own stock line, so you can top up the colours you run out of fastest without reordering the lot. Black and white tend to go first, for no reason anyone has ever properly explained.