Modify Roof Trusses for Loft

[bad_idea]

Hello all. I have a 30x40x12 garage I built about 5 years ago. Cinder block stem wall. 6" concrete slab. 2x6 studs balloon framed on gable ends. Scissor trusses. 7/16 OSB sheathing. 5/8 OSB roof deck. I'm in eastern NC, no real snow load to speak of.

I built two rooms on the left hand side - one 14x18, the other 10x12. The space above these two has a floor and I use it as a storage loft. Walking between the trusses isn't bad, but ducking under each truss is a nuisance. I would like to remove the trusses above the loft and frame it in a more traditional rafter system supported by a ridge beam. My question is, do any of you all think I can support 14' width of the roof on a beam supported between the exterior wall and the interior wall I built? The interior wall rests on the 6" thick concrete slab, no additional concrete under the wall. I do not want to cut out concrete and pour a thickened pad for a post to bear on. My hope is the load of the ridge beam spread along the wall is low enough the 6" slab can support it.

I am looking for ideas, will get an engineer to draw something up when/if I take this from idea to action. This is a pipe-dream kind of project. If I can't pull it off relatively inexpensive with minimal effort, I'll keep ducking under the trusses. I KNOW I should have designed this into the initial build, but the loft wasn't much of a thought when I built the garage.

 

[LXCam]

Sounds like a bad_idea to me....














OK, ya knew somebody was going to go there. I've got no input but I know you're certainly going to get some.

 

[mm08822]

Take your shop drawings and truss details to a structural engineer. Explain what you want.

All other answers will be useless/risky.

 

[billconner]

A little difficult to understand. I don't know which wall is supporting what and which direction is it in relation to gable and eave.

I don't think a wall or even a single column with the load of a ridge beam of some lengthbearing on the 6" slab is going to be a problem or the problem.

if the building is 30' wide, why not just put a post under new ridge beam, and not mess with walls? It's only a foot or less from the 14' wide (or 18' - don't know which) room wall.

I do think you have challenges installing the ridge beam/removing the trusses. Depending on truss design, maybe you can install a ridge beam while trusses are in place, and than install rafters - like 2x10s or 12s or whatever works for span and truss spacing - and kind of sister them to top chords of the truss. Then go back and cut rest of truss.

If you don't want the post to floor, put a 30' lvl across from top plate to top plate and set post on that.

Best I can offer based on what I know.

 

[jack stand]

Go back to your truss company. You being a past customer they might have their "guy" advise you for little cost. If you happen to have the truss paperwork from the original build bring it along with you, this would very much simplify things for them.

 

[CraigStu]

It certainly seems possible to me. But we could give much better thoughts w/ a simple hand drawn floor plan.

 

[billconner]

He's removing the trusses - bottom chord and webs - and replacing with rafters. What's the truss company going to do?

 

[strutaeng]

Anything is possible with money. Yes, it can be done.

 

[jack stand]

He's removing the trusses - bottom chord and webs - and replacing with rafters. What's the truss company going to do?

Just a WAG Bill, but short of completely re building the roof he's going to need to support the new ridge pole somewhere near the middle of his roof. Modifying the last trusses on either side of the new ridge pole to carry this extra load (if possible) would be the direct approach to this. I never considered additional posts in the middle of the 1st floor. That would be a non starter for me.
We've run into situations on site (someone screwed up) that the truss company worked out for us with adding lumber to certain areas along with nailing specifications.

 

[billconner]

Just a WAG Bill, but short of completely re building the roof he's going to need to support the new ridge pole somewhere near the middle of his roof. Modifying the last trusses on either side of the new ridge pole to carry this extra load (if possible) would be the direct approach to this. I never considered additional posts in the middle of the 1st floor. That would be a non starter for me.
We've run into situations on site (someone screwed up) that the truss company worked out for us with adding lumber to certain areas along with nailing specifications.

Can't tell for sure but "middle of the 1st floor" next to a 14' or 18' wide room in a 30' wide building wouldn't obstruct much. Maybe the wall can be extended.

 

[Hank11]

Take your shop drawings and truss details to a structural engineer. Explain what you want.

All other answers will be useless/risky.

This ^^^^^^^^^^^^^.
When you are done, it’ll be great.

 

[NUTTSGT]

Might be simpler to tear off the roof, add wall height and replace the roof.

 

[firebirdparts]

As a practical matter, I think it’s gracious overkill for that sort of building. I am assuming here that there is hard material under the floor. As a design/building code/proper matter, a foundation would have been the right thing to do. I don’t think any engineer will agree to a point load like that, but I could be wrong.

 

[billconner]

As a practical matter, I think it’s gracious overkill for that sort of building. I am assuming here that there is hard material under the floor. As a design/building code/proper matter, a foundation would have been the right thing to do. I don’t think any engineer will agree to a point load like that, but I could be wrong.

Let's say it's a 20' ridge beam. the column at the end supports 10' x 15' of roof. At 30 psf, that's only 4500 pounds. A 6x6 post on a 6" slab is effectively sitting on an 18" x 18" footing. That's 2000 psf, pretty minimal for most soils. If there's a decent base under it, the load is spread even more broadly.

 

[theoldwizard1]

I would like to remove the trusses above the loft and frame it in a more traditional rafter system supported by a ridge beam.

You can do it IF YOU INSTALL A TRUE RIDGE BEAM !! 4x6 would probably be adequate.

A ridge beam, is supported on each end by a column that goes down to the foundation. or down to another beam that spreads the load down to beams that goes down to the foundation.

This is very different than a ridge BOARD, which is basically a convenient place to nail the rafters.

 

[billconner]

Not mentioned, but you could just sister rafters to top chords of trusses, put in rafter ties and floor that for your storage, and cut out truss lower chords and webs. Might be easiest to modify rooms youve added but pretty simple and straight forward. If you could use the room walls for support, you could get away with dimensional lumber for rafter ties/attic joists Otherwise you might need to use TJIs to span 30'. Ultimately, I think simpler than a ridge beam and it's required support.