Hello all,
I've worked up a basic plan for the retrofit of two-story tall CMU exterior walls in a 1905 building (it suffered an interior fire with damage only to the second floor joists). The head joints in the CMU interior face were never filled, the CMU is chipped and gouged in lots of places, and it's unreinforced two stories high with the 2nd floor joists bearing into the CMU (or on a very questionable ledger) and the original roof trusses bearing on the top of the CMU walls with no visible connections.
Given the fact that this is in a seismic zone that is also occasionally hit by high winds, I'm just not comfortable signing off on the building until I know that those CMU walls can be counted on to carry the required lateral loading. I've recommended retrofitting rebar and grout but the contractor is balking at the cost. Access is available to the inside face of the CMU but not the outside - someone added a very questionable brick facade in the 70s or 80s (that's a whole separate issue). The building is seriously nothing special (and that's coming from a dedicated historic preservationist, but a realist). I'm not comfortable with carbon fiber strips because the CMU is in such questionable condition. I did think about building a steel frame interior to the CMU walls and using that to support the floor and roof, and perhaps providing lateral stability to the CMU, but that's crazy expensive too. The contractor asked me to consider using light gauge metal studs to support the floor and roof, and to support the CMU walls laterally, but I don't know that light gauge could take that kind of load. And, in the end, it's my stamp on the line.
Does anyone have any other suggestions of how to strengthen these old (and in poor condition) walls?
thanks!
Please remember: we're not all guys!
I've worked up a basic plan for the retrofit of two-story tall CMU exterior walls in a 1905 building (it suffered an interior fire with damage only to the second floor joists). The head joints in the CMU interior face were never filled, the CMU is chipped and gouged in lots of places, and it's unreinforced two stories high with the 2nd floor joists bearing into the CMU (or on a very questionable ledger) and the original roof trusses bearing on the top of the CMU walls with no visible connections.
Given the fact that this is in a seismic zone that is also occasionally hit by high winds, I'm just not comfortable signing off on the building until I know that those CMU walls can be counted on to carry the required lateral loading. I've recommended retrofitting rebar and grout but the contractor is balking at the cost. Access is available to the inside face of the CMU but not the outside - someone added a very questionable brick facade in the 70s or 80s (that's a whole separate issue). The building is seriously nothing special (and that's coming from a dedicated historic preservationist, but a realist). I'm not comfortable with carbon fiber strips because the CMU is in such questionable condition. I did think about building a steel frame interior to the CMU walls and using that to support the floor and roof, and perhaps providing lateral stability to the CMU, but that's crazy expensive too. The contractor asked me to consider using light gauge metal studs to support the floor and roof, and to support the CMU walls laterally, but I don't know that light gauge could take that kind of load. And, in the end, it's my stamp on the line.
Does anyone have any other suggestions of how to strengthen these old (and in poor condition) walls?
thanks!
Please remember: we're not all guys!
