Why can’t tempered glass be re-cut?
Tempering is a thermal process that puts the outer surfaces of the pane into compression and the core into tension. That stress equilibrium is what gives toughened glass its strength — and it is also why any post-furnace cut, drill or grind shatters the entire pane. ASTM C1048 (US) and EN 12150 (Europe) both define toughened and heat-strengthened glass as supplied to finished size with all edge prep, holes and notches completed before tempering. Practically: every opening dimension must be confirmed and frozen before glass leaves for the toughening line, because there is no recovery on site.
Glossary: wastage percentage→
What’s a typical breakage allowance for tempered glass?
Practitioner ranges commonly sit between 2% and 5% of glass value, with the upper end on large IGUs, structural-glazed assemblies and long-edge units that handle poorly. The figure is illustrative — there is no single industry benchmark — and the only number that matters for your business is the rolling closeout variance from your last six months of jobs. The discipline that separates well-priced shops from the rest is citing the breakage allowance as a named line on the quote and reversing the unused portion into closeout margin, rather than burying it in the glass sell rate.
Glossary: wastage percentage→
How do I price per-opening hardware multiplication?
Build the hardware as a structured assembly per opening type, not a bundled allowance. A casement window carries hinges, an espagnolette or shootbolt, handle, restrictor and trickle vent; a tilt-and-turn adds a Roto or Maco gear set; a sliding door multiplies tracks, rollers, interlocks and locks per leaf. Each component sits in your catalogue with its own cost. The opening then references the components, not a fixed price. When the supplier raises the gear-set 4%, every quote that uses it flags for review rather than silently re-pricing accepted work.
Glossary: variance→
How do I handle aluminium profile price changes mid-quote?
Two practical safeguards. First, version supplier price lists per catalogue revision so a quote captures the rate it was built on; if the supplier issues a new list, every saved template referencing it flags for re-pricing rather than silently using the new number. Second, attach a quote validity window — commonly 14 to 30 days for commodity-exposed metalwork — and require re-pricing on extension. Aluminium billet is LME-traded; primary aluminium has moved 30–40% in single calendar years (LME public data), so a stale quote on a slow client is exactly where margin disappears.
Glossary: variance→
What CWCT testing applies to commercial façades?
The Centre for Window and Cladding Technology (CWCT) Standard for Systemised Building Envelopes is the UK reference for curtain-wall and rainscreen test regimes. Typical type-tests include air permeability, water-tightness under static and dynamic pressure, wind resistance (serviceability and safety pressures), and impact resistance per the relevant building height and exposure. CWCT also publishes site-test sequences (e.g. hose test for water tightness) that are commonly written into commercial specifications. Treat the applicable test schedule as a named scope item on the quote — not as an unpriced "standard inclusion".
Glossary: variance→
How does FENSA compliance affect my install workflow?
FENSA is the UK Competent Person Scheme for replacement windows and doors in dwellings — registered installers self-certify Building Regulations compliance (Approved Document L thermal performance, Approved Document Q security on new dwellings, ventilation under Approved Document F) and notify the local authority on the homeowner's behalf. Practically, the install workflow needs to capture the U-value of the unit installed, the trickle-vent provision, and the FENSA notification reference — and surface those on the closeout pack the homeowner receives. Missed notifications surface years later at conveyancing, and become the installer's problem to remediate.
Glossary: variance→
