Which ASTM standards apply?

  • ASTM E2307 – fire-resistance of perimeter fire barrier systems (floor-to-curtain-wall joint) using intermediate-scale multi-story test. The main one.
  • ASTM E119 – standard time-temperature fire exposure and fire-resistance rating basis.
  • ASTM E84 / E136 – surface burning / non-combustibility of mineral wool.
  • UL 2079 (L-rating) – air/smoke leakage of joint systems; commonly asked with E2307.
Confirm the exact standards and ratings required by your local code, project spec and tested assembly listing.

✔ Do's

  • Install only the tested assembly: same mullion, slab edge, depth and mineral wool density.
  • Compress high-density rockwool 25–50% (per listing) so it stays tight under movement.
  • Support with Z-clips / clamps / angle brackets at listed spacing.
  • Seal at mullion, bracket and corner interfaces – these are the weak points.
  • Apply smoke seal coat and intumescent sealant to the specified thickness; tool it.
  • Inspect and photograph every joint before cover-up; keep records.

✘ Don'ts

  • Don't use loose, low-density or cut-and-patched wool offcuts.
  • Don't leave voids at mullions, brackets, splices or corners.
  • Don't skip clamps or let the wool sag or fall out.
  • Don't thin out the coating or sealant to save time.
  • Don't mix products outside the tested listing.
  • Don't close up before inspection.

Why zero tolerance?

Smoke, not flame, causes most fire fatalities. A 5 mm gap running along a floor edge acts as a chimney: hot toxic gas climbs the facade and enters upper floors, defeating compartmentation. The system is only as good as its worst 100 mm.

Why high-density, compressed rockwool?

Rockwool resists ~1000°C+ without melting. Compression (with clamps) keeps it tight against slab and mullion as the building moves, thermally expands and glass heats up. Low density or under-compression opens gaps and lets smoke through.