Roof sheating and RC columns in loft room 1

[greznik91]

Hi, Im dealing with a loft room - there are only outer bearing walls (masonry).

Plan dimensions are not that small - What bothers me is that there are NONE inner bearing walls in the loft, onyl outer walls.

With proper sheathing of the roof (above rafters) is it OK as far as stability of the walls go?

RC colums (3 m height) are supporting wood beams for a roof. Im wondering if I should designed them as cantilever or no? Im wondering if there may be only vertical force to consider since sheathing will most likely act like diaphragm and transfer any horizontal froces (wind) to the outer bearing walls.

Id like to hear some opinions on these 2 topics.

Tnx.

 

[dik]

Can you use a glulam/paralam beam at the ridge with dimensioned lumber roof rafters spanning from the outside wall to the ridge (metal straps at the ridge to keep rafters from 'sliding' down. The roof diaphragm can provide lateral support for your perimeter walls. Maybe have a pilaster on the gable wall to provide support for the ridge beam and stability for the wall.

Dik

 

[Nor Cal SE]

I also support the ridge beam idea as described by Dik, which serves to eliminate those 2 RC columns you've shown. I'm not sure how much they would even help you in those locations, and the lower column appears to take some floor space, would be nice to eliminate the columns.

Double check that in addition to having lateral transfer of diaphragm to walls, you also have proper out-of-plane-anchorage/sub-diaphragm load transfer per ASCE 7-10, Sec 12.11, as applicable for your particular Seismic Design Category.

 

[dik]

NorCal... good points

Dik

 

[n3jc]

But I think he will still need to support ridge beam somehow (in the middle of the span between gable walls)... So Im not sure how a ridge beam would help him?

 

[dik]

Span is only 30'... can use a glulam or a steel beam with wood added for appearance.


Dik