How to use glazing packers
Updated: 23 October 2026
The bag is on the bench, the colours do not match the last brand you used, and the frame is standing in the opening. How to use glazing packers comes down to order: pack the outer frame at the fixings, keep the drains clear, then support the glass, and stop if the frame twists. This is the sequence for a first fit or a shim job. Which bag to buy is the [glazing blocks comparison](/hub/diy-supplies/glazing-blocks). Peter F. did not install a window for this page. A qualifying purchase can earn a commission at no extra cost to you.
The bag is on the bench, the colours do not match the last brand you used, and the frame is standing in the opening.
The bag is on the bench, the colours do not match the last brand you used, and the frame is standing in the opening. How to use glazing packers comes down to order: pack the outer frame at the fixings, keep the drains clear, then support the glass, and stop if the frame twists. This is the sequence for a first fit or a shim job. Which bag to buy is the glazing blocks comparison. Peter F. did not install a window for this page. A qualifying purchase can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Shape | Footprint | Thickness | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  FUX FUX 100-piece glazing packers | Flat | 100 × 24 mm | 1–6 mm | 8.8 | about £11.99 | View offer |
| Alternative |  FUX FUX 40-piece glazing packers | Flat | 60 × 40 mm | 1.5–20 mm, 5 of each | 8.1 | about £16.49 | View offer |
| Alternative |  n/a U-shaped PVC glazing packers | U-shape | 60 × 40 mm | Title 1.5/3/5/10 mm; bullets differ | 0.8 | about £12.99 | View offer |
On this page
Two jobs in one bag
An installation packer sits between the outer frame and the opening, beside the screws. A setting block sits in the rebate and carries the sealed unit. A location block stops the unit walking sideways. One flat used for all three, without the system diagram, can bow the frame, load one pane, or cover a drain.
Flat packers go in before the load. A horseshoe slides around a screw that is already started. This set has one U-shaped listing and ten flats. Bridge packers are a third shape, and none of these titles is sold as one. A FUX ventilation channel is a groove, not a bridge for your profile. Sort by measuring, because these packs do not share one colour map.
Pack the outer frame
Centralise the frame before you chase a spirit level with random thicknesses. Sidey’s December 2024 guide uses corner fixings 150–250 mm from the corner and centres no greater than 600 mm, with packers at those points. Foam is not the only fixing. Eurocell’s Logik steps keep a 5 mm expansion gap while you pack.
The Glass and Glazing Federation’s section 3.12 says installation packers should keep the frame central, level, and square, and normally stay in place. On a door, extra packers beside hinges and locks are good practice. If the screw is already in, only a horseshoe can still slide in. Over-tightening bows the jamb and the diagonals stop matching. Ease the fixing and change thickness. Packers do not straighten a twisted opening.
Support the glass without blocking water
Glazpart puts setting blocks for a fixed light near the quarter points, generally not less than 30 mm from the corner, and wide enough for both panes. A narrower packer can load one pane and the edge seal.
VEKA’s Norscot guide keeps glazing blocks off the drain slots and uses bridge packers on the lower rail, minimum two, and more if the rail is longer than 1,500 mm. A flat plate across the slot dams the rebate. None of the eleven listings is a bridge packer. Buy that shape from the system supplier if the diagram shows it.
Using the same pack as a shim
Stored UK reviews use these plastics under decks, sheds, kitchens, and brackets. That is a fair shim. It is not proof the same piece is the right setting block for your unit. A 1–6 mm bag will not fill a 15 mm void unless you stack, and a stack can creep if the pieces are not the same depth. The FUX 40-piece set is the one here that lists up to 20 mm. One HuangXinyu review, in the shared file, says a couple of pieces were not the same depth. One EVOGES review still needed build-up bars because the window was the wrong size. Packers do not replace a unit that does not fit.
Common questions
Do packers stay in the wall?
Yes, in the Glass and Glazing Federation’s installation guidance. Installation packers are normally left in place and concealed, beside the fixings, so the frame stays where you set it. Take them out only if the fixing maker tells you to. Pulling them after the screws are tight lets the frame move. Setting blocks under the glass also stay. They are not temporary wedges you remove once the beads are on.
Can I stack two thin packers instead of one thick one?
You can, and a Spesh review says that set can be doubled up. Stack pieces of the same footprint, and check the stack is even. A HuangXinyu review found a couple of pieces that were not the same depth, so a stack of 3 mm is not automatically 6 mm. Stacking does not create a 20 mm piece from a 1–6 mm bag without a tall, less stable pile. For a deep shim, start with a set that lists the thickness.
What if I cover a drain hole?
Water sits in the rebate and finds the inside of the frame later. VEKA’s guide keeps glazing blocks off the drain slots and uses bridge packers on the lower rail. A flat packer across the slot is the mistake. If you have already glazed and you can see the slot is covered, the beads have to come off and the support has to be refitted so the path is open. Do not drill a random hole through the packer and hope it lines up.
What does over-tightening look like?
The frame was square on the diagonals, and it is not square after the driver clicked on. A jamb bows inwards, a door leaf drops, or the sash scrapes. Ease the fixing, change the packer thickness, and tighten only until the frame is held. The federation’s warning is that over-tightened fixings distort the frame. Foam around the outside does not undo that bow.
When do I stop and call someone?
Stop if the frame twists when you pack it, if the opening is structural or badly out of square, if the unit is cracked or misted, or if you cannot support both panes and still leave the drains open. Also stop if you are about to replace a window in a dwelling and you are not clear whether Building Regulations apply. A mixed pack will not carry that decision for you.
Related pages
Sources
Public UK sources and the amazon.co.uk listings compared on this page. Listings captured 21 October 2026.
- GGF installation guide, section 3.12 (retrieved 21 October 2026)
- BSI BS 8213-4:2016 summary (retrieved 21 October 2026)
- FENSA homeowners (retrieved 21 October 2026)
- GOV.UK building work, replacements and repairs (retrieved 21 October 2026)
- Glazpart glazing accessories (retrieved 21 October 2026)
- VEKA Norscot installation guide (retrieved 21 October 2026)
- Sidey survey and installation guide, December 2024 (retrieved 21 October 2026)
- Glazing Supplies Direct: how to use glazing packers (retrieved 21 October 2026)