The bottom exposed edge of the glass is 24 inches above the landing surface and the nearest edge of the glass is 40 inches horizontally from the bottom tread. A guard complying with the code stands between the landing and the window, and the plane of the glass is 24 inches back from that guard. The glass is annealed. What is the finding?
- Not a hazardous location; a complying guard stands in front and the plane of the glass is over 18 inches behind it
- BA hazardous location, because the glass is under 36 inches above the landing and within 60 inches of the bottom tread
This is the correct reading of the two measurements and it stops one step short. The provision has an exception for glazing standing behind a complying guard, and that exception is what this arrangement satisfies.
- CNot a hazardous location, because the bottom edge of the glass is more than 18 inches above the landing surface
The 18-inch figure in this arrangement is the horizontal setback from the guard, not a height above the landing. Eighteen inches as a bottom-edge height belongs to the large-pane criteria instead.
- DA hazardous location unless the guard in front of the glazing measures at least 42 inches above the landing surface
Forty-two inches is the guard height used in commercial work. Residential guards are measured against a different figure, and in any case the exception turns on the guard complying and on the setback distance.
Why A is correct
The two measurements bring the glass into the provision, and the exception takes it back out. A guard complying with the code stands in front of it and the glass plane is 24 inches back, which is more than the 18 inches the exception requires, so the location is not hazardous on this ground.
What this question is testing
Whether the candidate applies the stairway landing criteria and then checks the guard exception, and measures the setback from the guard to the plane of the glass.
On the job
Half-wall guards with windows behind them are common in split-level and open-stair houses. Two things have to be confirmed before the exception is allowed: that the guard actually complies, in height and in opening limitation, and that the setback is measured from the guard to the plane of the glass rather than to the wall finish. Where the guard is short or the glass is close, the exception evaporates and the pane has to be tempered.
Memory technique
A complying guard 18 inches out keeps the glass out of reach.
Exam tip
Find the rule, then look for its exception. This one has a guard and an 18-inch setback.
Where to look it up
IRC Chapter 3, glazing, hazardous locations at stairways and landings, with its exceptions.