Through-Penetration F/T Rating Calculator

Because they measure different failure modes under the ASTM E814 through-penetration firestop test method (also referenced as UL 1479, and adopted by reference in the International Building Code, Section 714, for firestop system approval). F-rating is how long the firestop blocks flame from passing through; T-rating is how long the far side stays cool enough not to ignite something nearby by conducted heat. Plastic pipe conducts and softens faster than metal, so whenever Penetrant type is set to plastic, the calculator caps T-rating at one hour below F-rating even though flame passage resistance is unaffected.

Metal pipe holds its shape in a fire and leaves the annular space roughly intact. Plastic pipe softens and burns away, leaving an open channel unless something closes it — an intumescent collar expands with heat and crushes that channel shut. The calculator sets Needs intumescent collar to 1 automatically whenever Penetrant type equals 2 (plastic).

Not for plastic penetrants below 4 inches. The engine uses the barrier thickness directly as fill depth for metallic, cable, and mixed penetrants, but for plastic pipe it enforces a 4-inch minimum fill depth regardless of a thinner wall, since the collar assembly needs that depth to seat properly.

Whenever either Opening width or Opening height exceeds 4 inches. This is independent of fill volume, fire rating, or penetrant type — it is purely a function of the opening's two dimensions, since larger openings in concrete or masonry typically need a form sleeve to maintain a clean, round penetration.