How do I replace a sealed unit?

You don’t need to replace the whole window — in most cases the failed double-glazed unit can be swapped out while the frame stays in place. The job runs as follows: carefully remove the internal glazing beads (see our comprehensive how to guide), noting their position so they go back the same way; lift out the old sealed unit and the setting/location blocks beneath it; clean up the rebate; offer up the new unit on fresh packers, ensuring it sits square and the glass isn’t bearing directly on the frame; then refit the beads, working the longest sides last so the unit is held securely.

The critical part is the measurement — you’ll need the exact width, height and overall unit thickness (e.g. 28mm), plus the glass specification (low-E, gas fill, spacer bar colour, and whether any pane must be toughened or laminated). Bring those details to your local SevenDay depot and the team will manufacture the replacement to match. If you’re at all unsure on the spec, our counter staff would always rather check with you first than see a unit come back needing a remake.