Architectural Masonry 1

[kieran1]

I recently designed a two storey steel framed shopping centre with the provision for an extra floor some time in the future. Having no specifiaction for the external cladding i allowed for an angle section at first floor around the perimeter of the building to catch the outer leaf of cladding at second floor and future third floor. I included for this as a masonry block with compressive strength 3.5N/mm2 would not have been adequate to carry the upper lifts of masonry under lateral and gravity loads. Once the job started on site i received a specification from the architect for an Architectural Masonary unit with a compressive strength 7.0N/mm2 I then decided to omitt the steel angle at first floor level as this masonry unit is capable of supportting three lifts of blockwork.
My dilema is that the client is mantaining that i should not have included the angle in the first place and that i was trying to cost him money. Does any one know where i can obtain literture specifiying a 3.5n/mm2 Architectural Masonry unit so i my justify my inital asssumtions to him.
He's a very difficult client. Kieran

 

[Mattman]

The American Standard for non-loadbearing concrete masonry units, ASTM C-129, specifies a minimum compressive strength requirement of 500 psi (3.5 MPa). ASTM C-129 covers both hollow and solid CMU.

As you have a steel frame, with the masonry serving as non-loadbearing cladding only, you can make a good argument for the 3.5 N/mm^2 assumption that you used.

Please note, however, that the CMUs covered by ASTM C-129 are not for exterior use in freeze/thaw conditions without protection.