Roof Windows and Skylights AHA (Activity Hazard Analysis / Job Hazard Analysis)

Updated 2026-06-23

A Roof Windows and Skylights AHA (Activity Hazard Analysis / Job Hazard Analysis) heads the group of glazed roof openings — roof windows, unit skylights, and framed skylight assemblies — and it exists to put the one hazard that kills at the center: the roof opening you install them into is a hole you can fall through. This AHA (Activity Hazard Analysis / Job Hazard Analysis) is a fall-through plan first and a glazing plan second.

Why roof windows and skylights needs its own AHA

Roof windows and skylights are glazed openings in the roof — daylighting units set into a curb or frame in the roof deck. What makes this group its own analysis, and what separates it from every wall-glazing product before it, is that installing a roof opening means creating and working around a hole in the roof, at height, that a person can fall straight through to the level below. The roof opening is the defining, fatal hazard: skylight and roof-opening falls are a well-known killer in construction, both the fall of a worker through an open or unprotected roof hole and the fall of a worker through a skylight itself — because an unrated skylight will not hold a person's weight and looks deceptively like a solid surface. Layered on that are the ordinary but serious hazards of any roof work at height (working on a roof surface, near roof edges, exposed to weather), and the glass handling of the glazed units (sharp, heavy, breakable glass, now overhead of the space below). So the defining hazards are the roof-opening fall-through (the killer), the roof work at height, and the glass handling. The detailed roof-window, unit-skylight, and metal-framed-skylight AHAs cover each product; this heading AHA makes sure the crew treats the hole as the fatal hazard it is before anything else.

Breaking roof windows and skylights into steps

The steps put fall-through protection first:

• Confirm the opening size, unit type, and curb/frame from the submittal
• Protect the roof opening before and during the work (cover or guard)
• Establish safe roof access and fall protection for the roof work
• Prepare the curb or frame in the roof deck
• Hoist and set the skylight or roof-window unit (glass/lift control)
• Flash, seal, and secure the unit
• Verify the opening is closed out and the unit is secured — no open hole left

The hazards step by step

The roof-opening fall-through (the killer)

The roof opening is the hazard that defines this group and the one that kills. From the moment the opening exists in the roof deck until the unit is installed and secured, it is a hole a person can fall through to the level below — and even after a skylight is set, an unrated or non-load-bearing skylight will not hold a person's weight, so a worker who steps or falls onto it goes through. Skylight and roof-opening falls are a recognized fatal hazard in construction. The controls are the roof-opening-protection fundamentals, and they are non-negotiable: cover the opening with a secured, marked cover rated to hold the load, or guard it with a rated guardrail, whenever it is not actively being worked; protect existing and adjacent skylights with screens, guardrails, or covers so no one falls through them; use personal fall protection for the crew working the open hole; and never leave an open or unprotected roof hole — not for a break, not to fetch material, not for a minute. The hole is the fatal hazard, and it is controlled continuously.

Roof work at height

The work happens on a roof, so all the roof-work hazards apply: the fall from the roof edge or a sloped roof, working at height with materials, weather exposure (wind that catches a unit or a worker, wet or icy surfaces), and roof-access safety. Establish safe roof access, fall protection at the roof edge and on any sloped roof, secure materials against wind, and account for roof conditions. A roof window or skylight install is roof work with an opening in it — both the surface and the hole demand fall protection.

Glass handling overhead of the space below

The glazed units are heavy, sharp, and breakable, and they're handled at the roof opening — so a dropped or broken glass unit is both a cut hazard to the handler and a falling-glass hazard through the opening to the space below. Handle the glazed units with glass-handling protection and equipment sized to them, control them during the hoist and set so they aren't dropped through the opening, and protect the space below from falling glass or tools through the hole. The opening that endangers the worker also lets dropped glass through to whoever is beneath.

Hoisting, sealant, eye, and weather

Hoisting units to the roof is a rigging/lift operation (match to weight, control in wind), flashing and sealing bring sealant chemistry (sealant cautions), and the glass and metalwork bring eye and cut protection.

A simple Roof Windows and Skylights AHA structure

Where the opening is the hazard through the whole job

Every step of this group circles the same fatal fact: there is a hole in the roof. The fall-through endangers the installer working the opening, the falling glass goes through it to the space below, and an unrated skylight set into it remains a fall-through hazard afterward. That's why the heading AHA leads with opening protection rather than glazing technique — the hole is present from the moment it's cut until the unit is installed and secured, and often beyond if the skylight can't bear a load. The single discipline that governs the whole group is: the roof opening is never left open or unprotected, and skylights are treated as holes you can fall through, not surfaces you can stand on. Get that right and the rest is glass and rigging; get it wrong and it's a fatality.

From the field: what actually goes wrong

The roof-opening fatality is one of the most persistent killers in construction, and it comes from the hole being left unprotected or the skylight being trusted as a surface. The open-hole version: an opening is cut or a unit removed, the cover comes off, and someone steps back into it or falls through while working — because "it was only open for a minute" or the cover wasn't rated or secured. The skylight version is just as deadly and more insidious: a worker steps or leans on a skylight — new or existing — that looks solid but isn't rated to hold a person, and it gives way, dropping them through. People die this way every year. The rule that prevents it is absolute: cover or guard every roof opening whenever it's not actively worked, protect every skylight as a non-load-bearing hole, and never trust a skylight to hold your weight. This heading AHA exists to hammer that before the crew gets to the glass.

The bottom line

A Roof Windows and Skylights AHA is a fall-through plan. The roof opening is a hole a person can fall through — the group's fatal hazard — and a skylight set into it remains a fall-through hazard because it won't hold a person's weight, layered on roof work at height and overhead glass handling. The controls are absolute opening protection (rated cover or guardrail whenever not worked, never left open), treating every skylight as a non-load-bearing hole, roof-edge and slope fall protection, and controlled glass handling that protects the space below. The detailed AHAs cover the products; this one makes the hole the first and last thing the crew thinks about.

Frequently asked questions

Why are roof openings and skylights considered a fatal hazard?

Because installing a glazed roof opening means creating and working around a hole in the roof, at height, that a person can fall straight through to the level below — and skylight and roof-opening falls are a recognized killer in construction. It's fatal in two ways: a worker falling through an open or unprotected roof hole, and a worker falling through a skylight itself, because an unrated skylight won't hold a person's weight yet looks like a solid surface. The opening is the defining hazard of the whole group.

How do we protect a roof opening during installation?

Continuously and without exception. Cover the opening with a secured, marked cover rated to hold the expected load, or guard it with a rated guardrail, whenever it isn't actively being worked; use personal fall protection for the crew working the open hole; and never leave an open or unprotected roof hole — not for a break, not to fetch material, not for a minute. The moment a hole is left open is the moment someone falls through it.

Why are existing skylights a hazard even when we're not installing them?

Because an unrated or non-load-bearing skylight will not hold a person's weight but looks deceptively like a solid surface, so a worker who steps, leans, or falls onto it goes through. Protect existing and adjacent skylights with screens, guardrails, or covers, and treat every skylight as a hole you can fall through rather than a surface you can stand on — this is one of the most persistent fatal mistakes in roof work.

Does the glass handling matter as much as the fall hazard?

The fall-through is the killer and comes first, but the glass handling has its own serious edge: the units are heavy, sharp, and breakable, and they're handled right at the opening, so a dropped or broken glass unit is both a cut hazard to the handler and a falling-glass hazard through the hole to the space below. Handle the units with glass protection and equipment, control them during the set, and protect the space beneath the opening.

Related AHAs and JHAs

• Roof Windows AHA — the operable roof-window detail
• Unit Skylights AHA — the prefabricated unit skylight detail
• Metal-Framed Skylights AHA — the large framed skylight detail
• Roof Opening Protection JHA — the roof-opening fall-protection fundamentals

Written by Mustafa Tok, CSP, ASP, CHST — OSHA Authorized Outreach Trainer with 14+ years of international construction safety experience across federal, heavy civil, and industrial projects.