Replacing a non-structural ridge board with a structural ridge beam

[Jeff Keith]

My wife and I recently moved to Maine. Long story short, we have an attached 14' by 20' building that has served as a woodshed, but is now going to be my new shop for the time being. It currently has exposed ceiling joists a little over 7' high providing structural support to the roof. I would like to open up that space a bit more, and I'm thinking about replacing the ceiling joists with collar ties and a structural ridge beam (see pic below).

The problem is how to do that without taking the roof off. In other words, the ceiling joists and ridge board would need to be removed in order to put the structural ridge beam in place (properly supported on each end of course), which would leave the roof temporarily supported by the walls only - not good. Could I get around that problem by nailing temporary vertical supports to the rafters and floor joists? Thanks!

Ridge.jpg

[Tom M King]

What size are the rafters? I feel like there's a way to do it a lot simpler than changing the ridge, like putting an LDL, or even built up of 2x12's, underneath the existing ridge.

[Jeff Keith]

What size are the rafters? I feel like there's a way to do it a lot simpler than changing the ridge, like putting an LDL, or even built up of 2x12's, underneath the existing ridge.

They're 2x6s at around 8' long each. The ridge board is a 1x8.

I had also thought about using beefy collar ties about halfway down the rafters rather than 1/3 the way, but I don't know if that would be enough to handle some of the snow loads we get, etc.

[Tom M King]

I don't have my Architectural Graphic Standards book here to look at the span tables, but I'm sure you could beef up under the ridge without taking it out. 2x6's should be plenty big enough reducing their span with the collar ties. With as steep a pitch as your drawings show, you should have plenty enough room for it. Your inspector might require an engineer to approve the design, but mine have always gone along with a design of my own when I showed them the span table used to do the sizing.

[Jeff Keith]

Thank you, Tom! I need to find one of those books...

[Eric Schmid]

I recently built a roof for a detached covered patio for a customer. The roof is 20 x 24 including 2' overhangs. Ridge is 2x 12, rafters are 2x 6. Ridge span is 20'. For spread resistance I used a few 1/2" x 10' lengths of all thread bolted through a Simpson DTT2Z on each end. The Simpson tension ties are mounted about 12" above ceiling joist height.

Although it still limits overall height, visually the all thread is hardly noticed; open feel. The installation is fast. The all thread can be tensioned enough to plumb the walls if needed. You could use this system as a permanent solution or to temporarily support the roof to retrofit a ridge beam.

As Tom suggested you can install a ridge beam under the existing board. Removing the existing ridge board seems unnecessary. It might need to be jacked up in the center if it's sway back currently. Make adjustments slowly over several days.

[Tom M King]

Google says there are a number of places where it's available for free pdf download now, such as: http://www.academia.edu/5835673/Arch...s_11th_Edition

[Jeff Keith]

Eric, that's an interesting approach I hadn't thought of. It would certainly open up the space and be far less intrusive, not to mention requiring less re-structuring. How many did you use for that 20' span?

Tom, thanks for the link. Unfortunately, it doesn't directly provide the PDF but ultimately directs you to a questionable website.

[Eric Schmid]

I believe 5, so approx. 5' OC. You would not need a ridge beam if you go this route, as you are simply changing the system for spread resistance. Tom's link may have it, but there are calculations for how far up the rafter ties can be placed for various conditions.

[Jeff Keith]

Thank you, Eric. I think this is the route I'm going to take. I've been looking through a bunch of examples on the net, and it's just a much more simple and elegant approach.

[Tom M King]

For no real reason, I just grabbed that particular link as an example from the page full resulting from my Google search for: Architectural Graphic Standards

[Jeff Keith]

No worries, Tom. I actually use academia.edu as a resource in my real job, so I was surprised to see that. I'm going to see if I can find a used copy of Architectural Graphic Standards. It will be extremely useful for this and other projects that I have in the hopper.

[Jim Becker]

I'll make the suggestion that once you have a direction you want to go, have a chat with a local structural engineer. While it might cost you a few bucks, in the end, it may be a valuable investment to insure that all the tees are dotted and eyes are crossed...

[Lee Schierer]

I'm not a structural engineer, but I would think you could put in your new cross ties and the put temporary support walls under them to take the roof load and may lift it slightly. Once they are supported, remove the existing ridge board, shorten each rafter, slide your new ridge beam in from one end and once it is lifted in place, attach the rafters to it with joist hangers. Finally remove the temporary wall and you should be good to go.

They do this all the time when removing a load bearing wall to put in a beam for the new open concept design in houses.

[Jim Andrew]

I can't imagine why you would need to change the ridge board on a 14 x 20 building, even if you are raising the ceiling. Personally, I would put your new ceiling joists up on the side of your rafters, then knock out the original ones, and call it good. Would hold them as low as possible. I have seen garages built without ceiling joists at all, and with the rafters just butted together with no ridge. And they were old at that time.