Reducing Effective Span on Roof Support Beam

[NimbleMotors]

In my current garage build I'm thinking of how to reduce the required beam strength.
I need room to move two cars around inside the 24x24 space, so having support posts in the middle is highly undesired.
I'm doing a sloped flat roof.

The first thing was I went from supporting the rafters with a single beam at the mid point (12ft) to using two of them at the 8ft and 16ft locations.
Then I moved the support posts from the walls edge in about 2ft, so now the clear span is only 20 instead of 24. This is all kinda straightforward.

What isn't so much is putting angled supports from the posts to the beam. I've read it does nothing to reduce the beam strength but then also it reduces the span to 1/2 of the angle distance. So if I have 2ft angle on both ends, the span is reduced by 2ft. This would lower my beam span to 18ft.

Then I was thinking can I remove one or more rafters in the middle of the beam and reinforce the space between them with cross structure.
I have found nothing about this doing any good, as all the calcs seem to just average the load into the center point.

Next idea is to add another support beam perpendicular to the two beams. Using the same techniques as above.

And finally I was wondering if I could have a removable support post, and just remove it when I need to move cars around.
Perhaps the roof would sag a bit with it removed, but that doesn't seem a problem as its just for a couple hours at most.

Yes I could hire and engineer, buy a proper LVL, etc, I would not be asking if that was an option.

 

[Youngandfree]

My crazy off the wall idea would be just buy a 24ft truss. Why make it so unnecessarily complicated?

 

[billconner]

Or use TJIs for rafters. Easy as can be.

 

[bb29510]

two beams with a piece of steel plate in middle

 

[joe_padavano]

My crazy off the wall idea would be just buy a 24ft truss. Why make it so unnecessarily complicated?

^^^THIS. Of course trusses mean that the side walls need to be able to carry the entire roof load. Not a big deal, just be sure to design for it.

 

[TRWham]

If this garage does not yet exist, just build it with LVLs that can span the entire length. Another option for a flat roof is to use steel bar joists that can span the 24' and avoid the beams entirely. You might even be able to source some salvaged or surplus bar joists.

 

[jkuro]

A Flat roof Truss will give you what you want with no beam.

http://www.cascade-mfg-co.com/files/media/rooftrussspanchart.pdf

 

[NimbleMotors]

1. Can you just move into an existing building? That would be easier.
2. Even easier, maybe not build cars anymore, that would resolve the issue.

If you are renting an existing structure that has rotted beams with center support posts, I can't help see 1 and 2 above.

 

[PCustoms]

1. Can you just move into an existing building? That would be easier.
2. Even easier, maybe not build cars anymore, that would resolve the issue.

If you are renting an existing structure that has rotted beams with center support posts, I can't help see 1 and 2 above.

 

[Youngandfree]

1. Can you just move into an existing building? That would be easier.
2. Even easier, maybe not build cars anymore, that would resolve the issue.

If you are renting an existing structure that has rotted beams with center support posts, I can't help see 1 and 2 above.

What kind of post is that? If you are implying you're renting a space with rotted beams, why not be an adult and just say it? , open ended queries with no context will never get you answers that you may find helpful.

 

[NimbleMotors]

What context is needed to determine the effects of techniques mentioned on the beam load?

I already said I'm not buying a LVL etc. An adult might have read that and not give a snide remark to use a LVL.

 

[PCustoms]

What context is needed to determine the effects of techniques mentioned on the beam load?

Context of what you're working on.

Your initial post suggests that you are building a new garage. Follow-on posts now suggest that you are repairing an existing garage, possibly one that you are renting. Being straightforward with all the facts will always yield better answers and suggestions.

As for the attitude and snide remarks, I've only seen that from one person in this thread.

 

[Youngandfree]

What context is needed to determine the effects of techniques mentioned on the beam load?

I already said I'm not buying a LVL etc. An adult might have read that and not give a snide remark to use a LVL.

I didn't mention LVL. You said my "garage build". That implies you're gearing up to BUILD a garage. Your lack of context and bad ideas for a removable post that may allow a temporary sag are telling.

 

[NimbleMotors]

It is a simple question about rafters (load) on a beam that needs no additional context.

The textbook analysis shows the rafter weight averaged to its center. The picture shows now two groups that averaged to their center, which is no longer in the center of the beam but more to the edge. This reduces the load in the center. Or not.

The angled support reduces the span. Or not.

The perpendicular support beam provides effectively a center post. Or not.

I have found over the decades that everyone wants to answer the question they have an answer for, not the question asked.

 

[NimbleMotors]

I didn't mention LVL. You said my "garage build". That implies you're gearing up to BUILD a garage. Your lack of context and bad ideas for a removable post that may allow a temporary sag are telling.

"Yes I could hire and engineer, buy a proper LVL, etc, I would not be asking if that was an option." hmm....
why is a removable post a bad idea, your comment is telling that I will get no useful information from you.

 

[PCustoms]

Delete

 

[PCustoms]

I have found over the decades that everyone wants to answer the question they have an answer for, not the question asked.

your comment is telling that I will get no useful information from you.

I think you should take a step back and consider that many people here are willing to help, but the content of your posts is preventing that.

 

[Youngandfree]

It is a simple question about rafters (load) on a beam that needs no additional context.

The textbook analysis shows the rafter weight averaged to its center. The picture shows now two groups that averaged to their center, which is no longer in the center of the beam but more to the edge. This reduces the load in the center. Or not.

The angled support reduces the span. Or not.

The perpendicular support beam provides effectively a center post. Or not.

I have found over the decades that everyone wants to answer the question they have an answer for, not the question asked.

Over years I have found people leave out important context in order to get an answer they want instead of the answer they need.

 

[Youngandfree]

"Yes I could hire and engineer, buy a proper LVL, etc, I would not be asking if that was an option." hmm....
why is a removable post a bad idea, your comment is telling that I will get no useful information from you.

You said your roof would sag when you remove it. That's a terrible idea.

You're worse than the guy with the terrible steps into his shed.

 

[tarmy]

Been here a whole 10 days and flinging **** at people trying to help or at the least trying to give you constructive thoughts.

Troll.

 

[Youngandfree]

It is a simple question about rafters (load) on a beam that needs no additional context.

The textbook analysis shows the rafter weight averaged to its center. The picture shows now two groups that averaged to their center, which is no longer in the center of the beam but more to the edge. This reduces the load in the center. Or not.

The angled support reduces the span. Or not.

The perpendicular support beam provides effectively a center post. Or not.

I have found over the decades that everyone wants to answer the question they have an answer for, not the question asked.

Running a center beam under the rafters like your pic is likely to still require it to be an lvl.

 

[CraigStu]

Assuming you are building a new structure. let's get to basics here. A triangle is stronger than a straight board. A truss is extremely simple to span 24ft. Mine span 28 ft. But, if you insist on a flat but sloped roof, then you need lvls or flat roof trusses. Yes you can go w/ something less and support it in the center of the span w/ something else. But that something else still has to span 24ft right? So your thinking is to build something that won't span 24 ft safely and add in something to help it do that span. I suppose an engineer can calculate how to do that, but is that going to be less expensive than doing it right in the first place. A thing to consider is your initial pieces will sit on a wall at each end so the load is spread over the length of the wall. To add in a second piece you need to consider that it's load will be born at two points. Those two points in the floor, or foundation, or wherever, need to be designed to handle that load. I think your idea is possible but you don't want an lvl or an engineer. Do you really plan to do this based on answers you get here? You expect us to tell you that your idea is OK? Really?

 

[Beemer]

Knee braces are not your answer. The connections needed to make them effective are a problem just as the effect they have on the posts.
When you see those things in wood framing and there are a few nails holding them in place, they are doing nothing.

You also mentioned pulling the columns in a couple feet. I know I'd regret that in my garage and would much rather bite the bullet and clearspan regardless of the cost. If sizing is of concern, why not consider steel beams and columns?

 

[Beemer]

"Yes I could hire and engineer, buy a proper LVL, etc, I would not be asking if that was an option." hmm....
why is a removable post a bad idea, your comment is telling that I will get no useful information from you.

Once your building inspector is involved, which he will be when you take your plans in for a permit, he might require that an Engineer design all beams. They do where I live so you might want to get a jump on that.

 

[egdede]

Maybe the OP was trying to say 'I'm renting and will not do anything other than replace 2 rotted posts; where can I place them' when he said 'in my current build'. "in my current build' sounds so much better than the 'shop I rent'.

 

[Innovate1]

Guessing from the location that an engineer will need to stamp the plans if this is new construction. Maybe the OP is talking about modifying an existing structure. Still need an engineer stamp unless they just do it without permits. Hard to tell...And the sketch isn't at all clear to me but I didn't spend much time trying to figure it out. People here are generally helpful but don't always give the answers desired. The poster then can use the info or not. Simple as that. No need to get worked up about things...

 

[billconner]

Slightly strange thread, not knowing if knew or renovation to start with. If new, just use rafters that will span 24'. If renovation, just sister an lvl to the existing beam and size it for the full load. Perpendicular beams are probably more expensive and harder to install.

 

[Innovate1]

Slightly strange thread, not knowing if knew or renovation to start with. If new, just use rafters that will span 24'. If renovation, just sister an lvl to the existing beam and size it for the full load. Perpendicular beams are probably more expensive and harder to install.

The OP seems quite set on NOT buying an LVL. It's not clear to me why...

 

[billconner]

Well, then a steel channel. And weren't the supporting beams perpendicular locks?

I suppose you could get creative and use truss rods. Kind of cool.

 

[wssix99]

Yes I could hire and engineer, buy a proper LVL, etc, I would not be asking if that was an option.

You are asking engineering questions here. None of the ideas you have will work structurally, but an internet discussion site really isn't the place to get an education in why. You should hire an engineer for your engineering problem.

Practicing engineers are professionals, just like doctors. Most have extensive post-graduate schooling and all have practical residencies and pass extensive board exams. You can't just read a book and figure this stuff out.

There's a guy who hangs out in my alley and would give you a free colonoscopy. My guess is that you'd pass and would rather pay a doctor for the service. This is the same type of situation. No matter what you read about this sort of thing on the internet, you should reach out to a professional engineer.

 

[Dig Doug]

If your building a new garage

easy to build and strong, and fairly easy to order up at 16“ oc only need 19, but I would get 20pcs

I would use TJI’s

TJI I-Joists

www.fp-supply.com