CMU - 2 hr - 53% filled - load bearing

[rbcameron1]

I need a clarification. Looking at a fire separation between 2 single family dwelling units. I require a 2 hr rating. As I understand the code, I'm just curious how the masonry "figures" 53% core filled. Table 720.1 (2) indicates a certain depth the CMU needs to be, for speed-sake, lets say its 4.0". I have an 8" CMU block (7.625" x 0.53 filled) = 4.04" So I would not need to core fill ANY of them to maintain a 2 hr rating.Would that be correct?

View attachment 2044

View attachment 2044

/monthly_2014_04/filled.JPG.2b90c811b1dace4ea7234aed9a2edcc5.JPG

 

[Paul Sweet]

ASTM C90 requires certain minimum thicknesses for the face shell and webs. The National Concrete Masonry Association has good information on their website:

http://www.ncma.org/resources/ConcreteMasonryUnits/Pages/FireResistance.aspx

TEK 2-1A & 2-05B give minumum face shell & web area. TEK 7-01C gives fire ratings based on equivalent thickness and aggregate type.