Roof Hatch Product

Overview

Every flat-roofed commercial building needs a way to get people onto the roof for HVAC service, drain cleaning, and inspections, and the roof hatch is the standard answer: an insulated steel or aluminum lid over a curbed opening, reached by a fixed ladder or ship stair from below. The common personnel size is 760 × 910 mm — sized so a climber on a vertical ladder can pass through with a tool bag — while 760 × 2,440 mm units serve ship stairs and oversized hatches pass equipment. It is an unglamorous product whose design is almost entirely about three things: keeping water out for decades, not injuring the person halfway up a ladder pushing it open, and not becoming the hole someone falls through.

Weather and thermal design

The Curb Assembly does the waterproofing. Rather than asking the roofer to flash a raw opening, the hatch arrives as a welded Curb Wall about 300 mm high with an integral Counterflashing; the membrane runs up the curb and terminates under the cap, the same detail as any rooftop unit. Height matters: 300 mm keeps the joint above ponding water and drifted snow. The Deck Flange carries loads into the deck, and Curb Insulation lines the upstand.

The Cover Assembly is a sandwich of Cover Pan, Cover Insulation, and Cover Liner, crowned so water sheds. Sealing is two-stage: the Overlap Flange skirts down over the curb so wind-driven rain must travel upward to reach the joint, and the continuous EPDM Cover Gasket closes what remains. Anything that does get past — including condensation, the real enemy in cold climates — lands in the Condensate Gutter and weeps back out. Energy codes have pushed manufacturers to thermally broken designs that separate inner and outer skins, since a plain steel hatch is a large thermal bridge that frosts on its underside; broken assemblies reach U-values near 0.5–1.0 W/m²K.

Operating safely from a ladder

The dangerous moment in a roof hatch's life is a person near the top of a fixed ladder, one hand on a rung, pushing a 30–60 kg lid open into the wind. The Lift Assist removes most of the hazard: two Gas Springs counterbalance the cover so net opening effort stays under about 90 N, damp the swing, and at roughly 70 degrees the Hold-Open Arm locks automatically so a gust cannot slam the lid onto the climber's head or hands. Closing reverses through the Release Grip, positioned for one-hand use, and the springs ease the cover down to where the Slam Latch snaps over the Strike Plate — secure without a separate locking step. The Inside Handle and Outside Handle operate the same bolt, and Padlock Hasps on both sides allow controlled access, with the firm rule that no locking arrangement may trap a worker on the roof.

All of the spring reaction and the 0.9 kPa wind uplift on an open lid funnel through the Hinge Set; the Hinge Pins are stainless and generously sized because a peeled-open hatch cover is a roof-borne projectile.

The fall-protection problem

An open hatch is, in OSHA's terms, a hole in a walking-working surface, and 1910.28 requires it guarded whenever uncovered. The Safety Interface package addresses this without touching the membrane: Rail Mount brackets bolt to the curb's cap flange and carry a three-sided Guard Rail Kit at 1,070 mm, with a self-closing Safety Gate across the access side so the perimeter is complete the moment the climber steps through. Below, ANSI A14.3 governs the fixed ladder; a Ladder Extension Post post telescopes about a metre above the curb so the climber keeps a handhold through the transition, aided by Grab Bars inside the curb. Retrofit of railings to existing hatches is one of the most common citations resolved on older buildings, since the hardware bolts on in an hour.

Variants

The same construction scales to equipment hatches with double leaves, acoustic hatches with rated covers near STC 40 for plant rooms over offices, and blast-resistant or security hatches in hardened facilities. Smoke vents share the format but add spring-open mechanisms and fusible-link release; a plain roof hatch opens only when someone pushes it.