Question on PPD practice exam - Historical building thresholds

In a PPD practice exam case study, I was asked this question regarding an existing threshold in a historical building.

The original stone thresholds are 3/4” high. Which is the best solution for the treatment of the thresholds to make them ADA compliant?

This is what it said the correct answer was and why.
Replace the thresholds with new stone thresholds, that slope down to 1/4” max slope of 1:2
Correct. The threshold should have a slope of 1:2 to be compliant.

This is an image in the preservation briefs that were included as supporting materials.

Shouldn’t the slope be 1:12? Is the 1:2 a typo? The explanation does not give enough information on why it is correct if it is supposed to be 1:2.

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Great question, and welcome to our ARE Community!

@cat.heard9 or @heatherrivera are either of you able to help us out on this practice exam question?

I believe what the question is getting at is knowledge and compliance of IBC 2015 1010.1.7 Thresholds. This states that raised thresholds greater than 1/4" must be beveled with a slope no greater than 1:2. You can have 3/4" threshold, but since it is over 1/4" in height, the beveling must happen. So to your original question, 1:2 is correct for a threshold. 1:12 is a ramp.

It’s certainly tricky; and I’m not entirely sure what the graphic is portraying without reviewing all of the supplemental reference material, but I hope the above explanation helps.

This is certainly something that is a great differentiation to know for the exam. Keep up the awesome work!


Thank you. I was able to find that in the IBC. Since the question had “ADA compliant”, I wanted to make sure the same was true in the 2010 ADA standards and I did find more supporting information.

404.2.5 Thresholds.
Thresholds, if provided at doorways, shall be ½ inch (13 mm) high maximum. Raised thresholds and changes in level at doorways shall comply with 302 and 303.
EXCEPTION: Existing or altered thresholds ¾ inch (19 mm) high maximum that have a beveled edge on each side with a slope not steeper than 1:2 shall not be required to comply with 404.2.5

Nice find! Those existing buildings always give you a bit more leniency. A bit - like 1/4".