Rafter Roof Span Question

[LimitedReality]

Hi All,

I've been a member for 5 years, but haven't really participated. Just enjoyed reading through posts. However, in the next 2 weeks I'll be moving from my current 2 story, 1000+ sq ft. 3 car garage, to a home with a tiny 20x20 2 car attached. The good news is from speaking with the local township (PA), it shouldn't be too hard to get approval to put up a separate garage on the property. Also good news, My wife (who hates how much time I spend in the current garage) surprisingly supports the idea and gave me the green light to proceed under two conditions: First, it needs to match the style of the new house AND second I need to get construction done before the end of the year. My projects tend to take years if I'm not given a deadline.

So, the reason I'm posting tonight is to see if anyone has suggestions as to how to solve a framing/structure question I'm having. The house has open ceilings, in order to match those open ceilings, I'm thinking I'm going to need to do rafters and a ridge beam. I'm looking to build a 28' wide x 24' deep garage, and the beam would run the 24' length. I'd like to avoid having a middle support in the way. Has anyone built something similar? I've searched the forum but most folks are using trusses when they go this wide.

I intend to build a small loft area over the garage door side, so only half the garage will be open to the ceiling. I'm attaching a sketch. An LVL or steel beam seem to be the logical answers, but then the question becomes sizing and I've some concerns about the expense. Just curious what others have done.

Any help, direction, comments or suggestions would be appreciated.

 

[JimRB]

Most people say match the style, they refer to the exterior look. A garage that looks like a house on the inside might lack some function.

 

[LimitedReality]

Agreed, so to elaborate on the style reasoning, the house has partial stone fronting, and these windows that go from the top of the door all the way to the roof line, in order to reproduce that, I need to not carry the loft all the way across (otherwise it'd be visible through the continuous glass window. Also, I do like the idea of having the open vertical space and light on that side as I'll be using it for wood working.

 

[maxpower_hd]

That is exactly how mine is built. I can try to find the drawings. But basically I have 3 14" lvls for the Ridge pole spanning the 24'. Traditional lumber for the rafters.Then collar ties between them for a vaulted ceiling.

I have a garage under on mine so I have wood I beams for the floor joists again with no beams or posts in garage. My local lumber yard helped me with sizing the engineered lumber.

 

[GMCGarage]

Hi All,

I've been a member for 5 years, but haven't really participated. Just enjoyed reading through posts. However, in the next 2 weeks I'll be moving from my current 2 story, 1000+ sq ft. 3 car garage, to a home with a tiny 20x20 2 car attached. The good news is from speaking with the local township (PA), it shouldn't be too hard to get approval to put up a separate garage on the property. Also good news, My wife (who hates how much time I spend in the current garage) surprisingly supports the idea and gave me the green light to proceed under two conditions: First, it needs to match the style of the new house AND second I need to get construction done before the end of the year. My projects tend to take years if I'm not given a deadline.

So, the reason I'm posting tonight is to see if anyone has suggestions as to how to solve a framing/structure question I'm having. The house has open ceilings, in order to match those open ceilings, I'm thinking I'm going to need to do rafters and a ridge beam. I'm looking to build a 28' wide x 24' deep garage, and the beam would run the 24' length. I'd like to avoid having a middle support in the way. Has anyone built something similar? I've searched the forum but most folks are using trusses when they go this wide.

I intend to build a small loft area over the garage door side, so only half the garage will be open to the ceiling. I'm attaching a sketch. An LVL or steel beam seem to be the logical answers, but then the question becomes sizing and I've some concerns about the expense. Just curious what others have done.

Any help, direction, comments or suggestions would be appreciated.

LVLs will be the way to go. You need to limit deflection so the rafters dont push out.

Your bigger issue will be the beam supporting the inside end of the loft. Are you going to span that 24' too??? More than likely that will need to be steel.

 

[LimitedReality]

LVLs will be the way to go. You need to limit deflection so the rafters dont push out.

Your bigger issue will be the beam supporting the inside end of the loft. Are you going to span that 24' too??? More than likely that will need to be steel.

In all honesty, the loft area could have a wall across supporting it reducing those spans into atleast thirds. So i guess the ridge beam can be more reasonable size.

It's the first floor span I'm concerned about. I assume steel would be the way to go there... Just a matter of figuring out how to size it and how to support it down to the slab. It appears steel is measured in kips and it seems to be some advanced math to get from snow load to kips. Anyone spanning 24 or more with a loft as well?

@maxpower - would love to see your drawings or any pictures you can share.

Thanks everyone so far.



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[matt_i]

and I've some concerns about the expense.

Personally I think you should revise if you are at all worried about money. What I see in your concept sketch should probably be designed by an architect.

Here's what I would do
- revise long pane of glass to 1 or 2 fixed rectangular window(s) + a little triangle window at the top, wood framing in between, trim with the stone on the outside.
- revise structural ridge to attic storage trusses, much less expensive. Coordinate the design of windows to miss the bottom chord.
- additional benefit to trusses is you get a ceiling for much more efficiently heating or cooling the space.
- put in an 96" tall door. No doors on an actual garage should be 84" tall if you ask me.
- I would also build 30x40 unless its out of reach finanicially or there's some other zoning-type restriction.

Hopefully this is helpful, its just designed to save some money (well, except for the last, you only get to add square footage once without incurring considerably more $)

 

[GMCGarage]

In all honesty, the loft area could have a wall across supporting it reducing those spans into atleast thirds. So i guess the ridge beam can be more reasonable size.

It's the first floor span I'm concerned about. I assume steel would be the way to go there... Just a matter of figuring out how to size it and how to support it down to the slab. It appears steel is measured in kips and it seems to be some advanced math to get from snow load to kips. Anyone spanning 24 or more with a loft as well?



@maxpower - would love to see your drawings or any pictures you can share.

Thanks everyone so far.



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If I read that correct, you would have two interior posts from the loft area up to the underside of the roof ridge beam, creating (3)-8 foot spans? Then, under the loft, you want it completely open?

If this is the case, that beam at the loft level just got bigger, since now you are picking up roof(snow) load, plus the loft load.

Call around to local engineers and have it sized properly.

You are essentially describing a transfer beam, and needs to be done right. If it comes down, the whole building does too.

Just a quick look at a beam design, you would be in the order of a 14" deep steel beam, or a 16" 3 ply LVL. All dependent on the way its framed with the floor.

 

[LimitedReality]

Personally I think you should revise if you are at all worried about money. What I see in your concept sketch should probably be designed by an architect.

Here's what I would do
- revise long pane of glass to 1 or 2 fixed rectangular window(s) + a little triangle window at the top, wood framing in between, trim with the stone on the outside.
- revise structural ridge to attic storage trusses, much less expensive. Coordinate the design of windows to miss the bottom chord.
- additional benefit to trusses is you get a ceiling for much more efficiently heating or cooling the space.
- put in an 96" tall door. No doors on an actual garage should be 84" tall if you ask me.
- I would also build 30x40 unless its out of reach finanicially or there's some other zoning-type restriction.

Hopefully this is helpful, its just designed to save some money (well, except for the last, you only get to add square footage once without incurring considerably more $)

Interesting idea Matt, that would keep the exterior look but increase function inside. There's just one challenge:
1. Figuring out how to minimize the size of the gap between the two windows. I think it'd throw off the look if it was more than 6" or so thick. I'll speak with a truss designer and see what the requirements would be.


@GMCGarage - Good point, it might actually be better to do two more substantial beams and split the load out to the walls. Just trying to think through options.

Thanks for humoring me.

 

[maxpower_hd]

In all honesty, the loft area could have a wall across supporting it reducing those spans into atleast thirds. So i guess the ridge beam can be more reasonable size.

It's the first floor span I'm concerned about. I assume steel would be the way to go there... Just a matter of figuring out how to size it and how to support it down to the slab. It appears steel is measured in kips and it seems to be some advanced math to get from snow load to kips. Anyone spanning 24 or more with a loft as well?

@maxpower - would love to see your drawings or any pictures you can share.

Thanks everyone so far.



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No steel I'm mine. Although sometimes I wish I had a beam to lift from. I'll see if I can get the drawing on the puter. No pics unfortunately. I wasn't computer savvy then.

 

[LimitedReality]

Thanks Max_Power, that'd be helpful.

Anyone else have pictures or drawings regarding how they did a 28' wide garage using rafters and the results?

 

[bczygan]

Any good local lumberyard will size the LVL beam for you.

Cost will be what it is.

Bill (Designer)

 

[maxpower_hd]

Any good local lumberyard will size the LVL beam for you.

Cost will be what it is.

Bill (Designer)

The lumber yard actually changed the size and had me change the drawing after they calculated the loading and span. I think I had two LVLs and they wanted three. Then they provided an engineering sheet and stamp for the inspector. All part of the price of the lumber. No additional cost.

 

[Throbbin Rods]

I used truss joists in my 28x28. Gave me a clear span and more than enough moxie to use the second floor for storage. I put them every 16 inches.

 

[kbs2244]

Ridge beam is the way to go.
It will give you a tremendous open space.
Your drawing shows room for the vertical post under the ridge as needed.

I would go with a steel "I" beam vs LVL.
Smaller and easier to lift into place.
Mine is a 8 inch depth across a 22 foot span with no problems.
4 inch tube vertical posts.
Your local iron shop will know the details.
The 8 inch was much more than I needed but is what they had in stock.

Rafters in ridge beam construction are under tension and keep the walls from spreading.
The ridge will not need supports but the loft may.