Remodeling a clubhouse ceiling 5

[Triangled]

Hello,
My client is wishing to add some volume to the ceiling area in a room for a local clubhouse. His concept is shown in the attached sketch which essentially is the removal of the bottom chord and the modification of the webs of the wood trusses.
I'd like to help him out but I'm having difficulty envisioning how to make this work.
I am concerned both for the lateral support for the masonry walls, although this is not in a major seismic area, and I am concerned regarding the scissoring action of the proposed configuration.
I would sure appreciate some ideas.
Thank you.

 

[AELLC]

I think the only way this may work is to rip the roof off entirely and go in with new trusses, and they will have large top chords to prevent the scissoring.

Why not get a preliminary design from the truss company to see if the new trusses will work?

 

[CANPRO]

It looks like the new ceiling height puts the new cross-member too high up to be an effective collar tie. I would also suspect that the top chord of the truss would need a decent amount of reinforcing it this arrangement as well, especially if you want to keep the masonry walls from kicking out.

Can your client live with exposed beams or bulkheads? If that's the case you can run two new beams in the 30' direction (assuming that's the only area he wants remodelled). Put the beam on each side where the rafter meets the new collar tie. He even has walls there to hide the posts. This should also reduce the demand on the top chord of the truss.

 

[JacksPanic]

Can you use a ridge beam to span the 30ft ? You only need to stiffen the walls and possibly the truss top chord which becomes the rafters.

 

[kieran1]

Maybe you can run two steel purlins the 30ft span to reduce the thrust on the walls from the removal of the botton chord. These could also support the rafters. However the span may require a large section and the temporary works required will be a difficult construction.

Kieran

 

[XR250]

You could cut up the trusses and install a 30' long structural ridge. You would may have to sister up the top chords when you are done depending on how they want it to look. As was previously mentioned, sometimes it is easier to tear it off and start over. Also, the fireplace may make it tricky to support a ridge.
When I run into this situation, most builders want to do everything from the inside without tearing the entire roof off.

 

[CANPRO]

I don't think a single 30' ridge beam would be the way to go...for a few reasons.

Its probably more work to install a single ridge beam rather than 2 new beams at the new ceiling height. You have to get the single beam up higher and it will be heavier than the 2 beam option.

Single ridge beam will make the temporary shoring harder because now you need two runs of shoring to keep everything balanced. If you use 2 beams, you can use one central set of temporary shoring and install 1 beam at a time. I don't think the temporary shoring is that difficult...the dead load of the roof is relatively small, you can span temporary beams between the new collar ties and then post down from the beams to support the roof (just how I pictured it, I'm sure there are other ways).

Using 2 new beams will support the top chord (now the rafter) within its span and this will reduce the demand on the rafter. The single ridge beam at the top will require more reinforcing on the rafters.

The new roof truss option may end up being cheaper. But there are risks and challenges with this option as well.

 

[Triangled]

Thank you everyone. This has really helped me mentally prepare for Monday.

I proposed the new truss option to the client which was, as suggested above to be expected, not received with much enthusiasm. But, of course, after considering the alternatives, who knows but that the client may return to this concept with renewed interest at a later date?

I think I'll develop the longitudinal beam alternatives, studying the one beam, and the two beam scenarios, and maybe even a three beam scenario (combining the one and two beam).

I am thinking of improving the connection of the CMU to the rafters (soon to become rafters after the truss configuration is removed) to provide lateral support to the top of masonry walls.