Can 6" masonry be used to satisfy the impact resistance criteria in Florida?
The FBC, 6th edition, Building, Section 1626.4.1 allows for 8" hollow masonry to meet the impact criteria for the HVHZ (Dade and Broward). Although there is no mention of 6" masonry 1626.4.4 allows for 2" of reinforced concrete to meet the requirements also.
Common sense would grant that solid grouted 6" masonry is going to perform better than 2" of poured concrete but again it is not mentioned directly.
That being said, FEMA P-320 Safe Room Const Plans specify 6" masonry with a #5 bar in a grouted cell at 16" o/c.
The more stringent FEMA P-361, Safe Rooms for Tornadoes and Hurricanes, 3rd Ed, March 2015 allows solid grouted 6" masonry with a #4 bar at 32" o/c.
As a side note, we plan to submit a code change to include solid grouted 6" masonry in the "deemed to comply" list under 1626.4 in the 7th Edition FBC. It is not currently listed simply because the issue of its use rarely comes up.
In summary, I can see no good reason why a building official would reject solid grouted 6" masonry as specified in P-361 as being acceptable for missile impact requirements in the HVHZ.
I have an 8' freestanding masonry screen wall adjacent to a building. Should the building be connected or not to the enclosure wall? In one location there is a doorway in the screen wall almost adjacent to the building with only an 8" piece of masonry between the building and the door opening. This 8" piece of masonry sits on the building foundation. Should this also be connected to the building or not?
If the wall is supported by an independent foundation I would definitely recommend putting a full separation control joint between the wall and the building to account for differential settlement of the two foundations.
The short section of wall sitting on the building foundation is trickier. Since it sits on the building foundation it is unlikely that there would be any vertical movement between the wall and the masonry door jam. In this case I would recommend solidly attaching the door jam to the building wall. This would also give the wall some additional out of plane strength to resist wind loads applied to it from the door. This will, unfortunately, create a stress build up at the underside of the lintel where it sits on this short section of wall. The stress is from the screen wall changing length from moisture loss or temperature change OR the foundation supporting the screen wall settling at a different rate than the building foundation.
This control joint would be a standard joint at the corner of opening that runs under the lintel bearing horizontally for 8" then turns and runs up to the top of the wall or the underside of the bond beam, whichever works structurally. If there is a vertical bar adjacent to the opening it can pass through the horizontal plane of the control joint (slip joint) without completely negating the value of the joint.
Links to additional information:
NCMA TEK 10-2C - http://ncma-br.org/pdfs/130/TEK%2010-02C1.pdf
Don Beers, PE, GC