Hello -- I am new to this excellent site.
Situation: my contractor designed a simple 2-car carport to be attached to the front of our 5/12 pitched existing garage/structure (ES). The carport will have a traditional shingled roof, built on common trusses, and the whole structure will be supported at the ES as well as on four posts sitting on concrete footings. D = 20', W = 20' and 1st post out from the ES is at 10', 2nd post located at 20'.
I have an AST in Mechanical Engineering and my brother has been a working Civil / Structural Engineer for decades. Our independent calculations RE uplift in a 90mph zone agree. But a gal at the county code office has taken issue. We used standard uplift concepts RE psf on the roof etc. and in accord with how the load path would dictate the amount of concrete required at each footing.
The lady at the code office is not using any of this, but instead is insisting that the truss mfg. spec on uplift reactions (460 lbs at each end of the truss connection to the top plate) is the guiding principle. Thus, she has taken the 460, divided this by 2 (for something of an average), multiplied the 230 by 10 (1/2 the D dimension) and comes up with 2.3 kips. The foundation pad then, at this 10' post requires 16.9 cu ft of concrete weighing 2,535 lbs! Our calcs, with a safety value, indicate 1,600 lbs. required.
In addition to this she is saying that the existing 26' long by 1' wide, by 18' deep footing at the ES (which weighs 5,850 lbs) would have to beefed up as well.
So, off the record and with promises that I will treat any input as opinions only, I have a few questions:
1) does this seem reasonable?
2) is the use of truss uplift reaction specs the new way to figure forces required at the foundation?
3) any tips on presenting a case to the code folks? The code lady is saying I need to hire a licensed engineer to present the case.
Thanks for taking the time!
PianoGuy
Situation: my contractor designed a simple 2-car carport to be attached to the front of our 5/12 pitched existing garage/structure (ES). The carport will have a traditional shingled roof, built on common trusses, and the whole structure will be supported at the ES as well as on four posts sitting on concrete footings. D = 20', W = 20' and 1st post out from the ES is at 10', 2nd post located at 20'.
I have an AST in Mechanical Engineering and my brother has been a working Civil / Structural Engineer for decades. Our independent calculations RE uplift in a 90mph zone agree. But a gal at the county code office has taken issue. We used standard uplift concepts RE psf on the roof etc. and in accord with how the load path would dictate the amount of concrete required at each footing.
The lady at the code office is not using any of this, but instead is insisting that the truss mfg. spec on uplift reactions (460 lbs at each end of the truss connection to the top plate) is the guiding principle. Thus, she has taken the 460, divided this by 2 (for something of an average), multiplied the 230 by 10 (1/2 the D dimension) and comes up with 2.3 kips. The foundation pad then, at this 10' post requires 16.9 cu ft of concrete weighing 2,535 lbs! Our calcs, with a safety value, indicate 1,600 lbs. required.
In addition to this she is saying that the existing 26' long by 1' wide, by 18' deep footing at the ES (which weighs 5,850 lbs) would have to beefed up as well.
So, off the record and with promises that I will treat any input as opinions only, I have a few questions:
1) does this seem reasonable?
2) is the use of truss uplift reaction specs the new way to figure forces required at the foundation?
3) any tips on presenting a case to the code folks? The code lady is saying I need to hire a licensed engineer to present the case.
Thanks for taking the time!
PianoGuy
