Installing trusses on concrete block wall

[jimtheengineer10]

The building has concrete blocks walls and a flat roof. The owner is looking to install pre-engineered roof trusses with a 5:12 pitch as the the existing roof is leaking. There is about a 12" curb with a 2x10 top plate. What is the best way to fasten the trusses to the existing wall?

 

[dhengr]

Jimtheengineer10:
Elmer’s Glue?
Maybe some meaningful engineering and design info. would be in order here, along with some sketches of the existing wall and roof conditions, that is..., if you expect any meaningful discussion on your problem. We can’t see it from here.

 

[jimtheengineer10]

Attached is a picture showing the exterior wall and another picture showing the curve on top.

 

[jimtheengineer10]

Attached

 

[oldestguy]

One option would be to leave the flat roof in place, beef up the CURB, possibly with grouted fill as needed in blocks, plus anchor rods for the truss and rest them on the curb, with overhang to drain off over the ends. This assumes foundation can take any added loads from this. Or tear off the curb and the old roof and go from there.

 

[jimtheengineer10]

I was thinking of having the contractor remove the 2x10 top plate and install anchor bolts at 4'o.c. grouted into the concrete block wall. Then install a double top plate and fasten the trusses to the top plate with hurricane ties.

 

[oldestguy]

How bad is the roof situation now? Would not a guaranteed roof replacement membrane be a whole lot cheaper?

 

[dhengr]

Jimtheengineer10:
When you do something that significant in structural terms, you may have to bring the whole structure up to current code standards. Is the existing roof structure shot? Why not re-roof it, and install several inches of sloping insulation to improve the drainage? Of course, you have to evaluate the roof drainage system, be it roof drains, scuppers, or whatever, and incorporate that into the re-roofing job. What drainage system exists now? Nice pictures, but you’re still keeping all the important roof and wall details secret. What is the existing roof structure, its connections to the wall, and the wall construction details? When you put A.Bs. in at 4' o/c what are you actually grouting them into, at the conc. blk. and at the brick? Is there a top bond beam, can you grout down several courses, etc.? Or, will any roof uplift just lift a single conc. blk. out of the wall with your new A.B.?

 

[DaveAtkins]

I think you are on the right track. I did something similar for a church many years ago.

As others have mentioned, make sure everything you do meets code. I would especially be concerned with the fire rating issues--figure out what Type construction it can be, and then you can determine if you can use wood trusses.

DaveAtkins