Originally Posted By: R. Michael Gray, P.E.
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I inspected a house Friday and saw something I had never seen before. The house was 2 story and had a den in the rear with a fireplace at the rear of the den with the fireplace at the rear wall. The ceiling went all the way to the top of second story; also, there were no ceiling joists since it was all open. Sheetrock covered rafters ran from the top of the side walls of the den to the ridge above. With this configuration, the ridge is structurally a ridge beam and not a ridge board.
The owner was the original owner. Here is the history of the problem. There was never any sign of a structural problem until a third roof covering was applied. The original roof was wood shingles. The second roof was a composition shingle overlay. When it came time for a 3rd roof, the wood shingles and the composition shingles were removed, new plywood decking was installed and new composition shingles were installed. Shortly after that, the ridge began to visibly sag and there was obvious distortion in the side walls and in the rear wall that housed the fireplace.
Eventually the situation got so bad that they called in an engineer. He did not, apparently, put any report on paper but contacted a repair contractor and verbally told him what to do. Essentially they took the distressed roof down, realigned the side walls and constructed a new roof using a microlam as a ridge beam. At the inside end of the ridge beam (the front of the den) the ridge beam was supported in a wall in a conventional manner. At the fireplace end, they supported the ridge beam with a "large piece of angle iron".
The original ridge beam was a 2-ply 2x12 and was clearly inadequate. To make matters worse, the support at the fireplace end of the original beam was nothing beyond the friction between the beam and the brick. I am sure the carpenters intended to go back and resupport it but something happened. The additional load from the new roof plus the vibration from the work was just too much.
The cost to repair was $32,000 and this was 10-years ago.
Now they want to sell the house and they have nothing on paper. lI was there to write an opinion as to whether the repair was adequate. Since there was no design to review and almost everything was not visible , I explained that I could not verify the adequacy of the repair design. I could however inspect it from a performance perspective and provide an opinion addressed to that issue.
There was no sign of any distress or sagging that would indicate a problem.
But this whole episode got me to thinking. I have no problem with the ridge beam support in the load-bearing wall at the front of the beam. I made some quick calculations and the ridge beam itself is marginal but okay. That leaves the support at the fireplace end. Apparently they attached the angle iron to the fireplace chimney brick with some large bolts. If this ever gets in trouble, it most likely be at this connection. But I do not know how else this could have been repaired without at least doubling the cost.
I am curious about a couple of issues. I have seen this type of arrangement before in completed house and, frankly, have never questioned the connection or load path at the fireplace end. If I were designing it, I would have the ridge beam rest on a steel beam supported by two steel pipe columns that would take the load to the foundation. The angle iron connection and the use of the brick to transfer the loads to the foundation are not, in my mind the best solution although, in this case, they are working.
Question #1: Does anyone know how this is normally done in new construction?
Question #2: Has anyone seen this repaired differently than was the case in this house?
R. Michael Gray, PE
Professional Structural Engineer
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