Am I missing something?

[JBI]

From the 2012 IRC (same in the 2009 and 2006...)

R406.2 Concrete and masonry foundation waterproofing.

In areas where a high water table or other severe soil-water conditions are known to exist, exterior foundation walls that retain earth and enclose interior spaces and floors below grade shall be waterproofed from the top of the footing to the finished grade. Walls shall be waterproofed in accordance with one of the following:

1. Two-ply hot-mopped felts.2. Fifty-five-pound (25 kg) roll roofing.3. Six-mil (0.15 mm) polyvinyl chloride.4. Six-mil (0.15 mm) polyethylene.5. Forty-mil (1 mm) polymer-modified asphalt.6. Sixty-mil (1.5 mm) flexible polymer cement.7. One-eighth-inch (3 mm) cement-based, fiber-reinforced, waterproof coating.8. Sixty-mil (0.22 mm) solvent-free liquid-applied synthetic rubber.

My question is in regard to the underlined items. A 'mil' is a unit of measure equal to 1/1000 of an inch, and numbers in parentheses (generally) are metric equivalents of our non-metric measurements.

Why is item 6 mathematically consistent with other listed options, but item 8 is not? Am I missing something?

 

[Mac]

Because item 8 is a misprint?

 

[JBI]

That was my knee-jerk reaction Mac. Not only a consistent 'mistake' in every ICC code cycle, but NYS has the exact same 'mistake' in ours as well...

 

[31 Street Rod]

Figure R406.2 in the 2006 IRC Commentary, item #8: 8.6 mil solvent-free-liquid-applied synthetic rubber.

It seems like the information is correct in figure R406.2, but was transferred incorrectly to the body of the code.

 

[JBI]

And we have a winner! Kudos 31 Street Rod, nice find. (Same figure detail in the 2012 IRC w/Commentary BTW).

Still doesn't explain an unnoticed typo for 3 code cycles.

In multiple jurisdictions. :-/

 

[JBI]

Received a reply from ICC (two actually, but the first basically said 'that's what the code says, we can't change it'), it was a transcription error from the original proposal. Errata to be published.