Detached 30x38 question about center beam

[bdbull]

Just joined yesterday. Great forum with lots of great resources.

I'm in the planning stages of a new detached 30x38 3 car garage (see mockups here). The preliminary plans I've gotten so far call for a beam that spans the width (38') of the garage right down the middle. I'm assuming this will need to be some type of LVL beam to carry that large of a span, but I'm concerned about the placement. Currently it is called for it to rest over the large window on the left side of the structure. That doesn't seem wise to me...to put such a large beam over a window. 1) Should it be placed there and 2) if so, does the window header need to be sized differently than normal?

Thanks...this is my first of what is sure to be numerous posts on here.

 

[RWorth]

If it were me I would move the window and use a steel beam, I tend to overkill everything and a post in my opinion is safer than a beam to support a beam.

I'd use an I-beam because you can run a trolly on it for a hoist. Very handy, I have one in my 26x40 shop.

 

[bdbull]

If it were me I would move the window and use a steel beam, I tend to overkill everything and a post in my opinion is safer than a beam to support a beam.

I'd use an I-beam because you can run a trolly on it for a hoist. Very handy, I have one in my 26x40 shop.

I'm thinking I should probably get rid of the oversized window and just have two "normal" windows like the other side. That would at least allow me to put good support under the beam, posts like you mentioned.

I'm not a car guy so a hoist isn't something I'm worrying about. The garage is just for parking cars, lawn mowers, bicycles, scooters, and whatever else my kids can leaving laying around.

 

[glentre]

Agree that supporting a beam that size over a window is not a good idea. Supporting columns on the ends at the wall is the best way.

Another idea you might look into is using engineered wood joists or trusses for the ceiling instead of steel. These would span the 30 ft dimension, give you a flat garage ceiling and likely be less cost than steel. On my 30 x 38, I looked into all three options and found attic trusses to be the cheapest as well as giving me space above for ample storage or a future apartment. If you are interested, check my build, "30 x 38 full circle garage".

Glen

 

[firebirdparts]

The reason they did that is that 38 feet is a long way, and 30 feet is a long way. The window, if it's 6 feet wide, that's not a long way. Holding up the 2nd floor is serious business. The window is not really the problem. You can put two window and toughen that up if you want to.

 

[GMCGarage]

Just joined yesterday. Great forum with lots of great resources.

I'm in the planning stages of a new detached 30x38 3 car garage (see mockups here). The preliminary plans I've gotten so far call for a beam that spans the width (38') of the garage right down the middle. I'm assuming this will need to be some type of LVL beam to carry that large of a span, but I'm concerned about the placement. Currently it is called for it to rest over the large window on the left side of the structure. That doesn't seem wise to me...to put such a large beam over a window. 1) Should it be placed there and 2) if so, does the window header need to be sized differently than normal?

Thanks...this is my first of what is sure to be numerous posts on here.

Im doubtful they will get a LVL to work, and span 38 feet without a column in the middle. I tried a 7x24 spanning 38', no good at all. Steel beam, was in the W18x50 range.

Is this the architect doing this, or the engineer?

I would rather try and use a floor truss or TJI and span 30'-0" across, no columns.

 

[jchetty]

Welcome to Garage Journal. I am not nearly as experienced with most of the guys here- but I will say this- It is much cheaper to address it now.

My issue- dad’s was done with a ridge board instead of a ridge beam. If the terms are incorrect, I apologize. But this means that the main garage floor is obstructed by 2 lally columns.

From what I understand, a ridge board is a 2x board and the rafters are nailed to it. A ridge beam is a structural post that is placed horizontally under the rafters. Done correctly, you only need support to the ends. If you use steel- same idea- only have to support the ends as longs as the end posts are sized correctly. Would have been much better to use end posts even if I had to do bump outs in the walls. A clear garage floor would be a game changer.

Speak to someone and see if the center span will have to be supported. My dad’s garage specified none. The plans were done and everything. But during final inspection, they said it needed support. It was built 15 years ago and I was in high school and didn’t know then what I know now.

 

[bdbull]

@glentre - Took just a quick look at your build thread. Wow! That is almost exactly what I am doing. Just from the quick look I took, the only difference between yours and mine is you have dormers and I'm doing a double or cross gable on the front. Would you mind sharing your plans?

I'm beginning to think I hired the wrong guy to do my plans.

I've looked at the attric trusses, but was under the impression that I could not use them because of my roof design.

 

[jives]

I would rather try and use a floor truss or TJI and span 30'-0" across, no columns.

^^This. Having a clear span garage is a good thing. While one or two columns can be done nicely to split up the bays, they can also limit use of the space.

 

[bdbull]

I would rather try and use a floor truss or TJI and span 30'-0" across, no columns.

Are floor trusses used to create the entire floor support or are they used as a beam to hang perpendicular floor joists from?

 

[cdestuck]

That window isn't that wide and unless your contractor is a dummy it won't be hard to manage that weight. I would not alter your plans. And the beam isn't going to be handling near as much weight as the front and rear walls

 

[yeldogt]

I'm confused? Looking at your drawing ......the three doors have space between them? A support will go between the doors .......That's what holds the roof structure. Header over each door ... that window is nothing to worry about.

The picture you found on the internet is more in keeping with the house -- you should always try and match the roof slope. That flatter roof .. well .. it looks like an amateur.


Also -- the weight carrying ridge is only needed if you wish to eliminate the collar ties. You end up with a noticeable beam down the center -- or you have to frame a second set of rafters to hold the ceiling .. basically a scissor truss.

It's often cheaper to order them -- the scissor truss

 

[bdbull]

I'm confused? Looking at your drawing ......the three doors have space between them? A support will go between the doors .......That's what holds the roof structure. Header over each door ... that window is nothing to worry about.

I was worried about the window because that is where the 38' beam will be sitting, directly over the top of the window. Maybe it would be a better design to use two beams across the 30' span, one each between the garage doors. Is that even possible? (I clearly don't know what I'm talking about.)

The picture you found on the internet is more in keeping with the house -- you should always try and match the roof slope. That flatter roof .. well .. it looks like an amateur.

The roof will be 12/12 just like the house. Haha, I wouldn't even call myself an amateur.

Also -- the weight carrying ridge is only needed if you wish to eliminate the collar ties. You end up with a noticeable beam down the center -- or you have to frame a second set of rafters to hold the ceiling .. basically a scissor truss.

It's often cheaper to order them -- the scissor truss

For some reason trusses make me feel better. I guess the fact that they are engineered to a particular specification just gives me a warm fuzzy. But how could I do trusses with the double/cross gable design? Is that possible?

 

[yeldogt]

It's just a question of what required for the main ridge (if you want to have an open space and no supports) the front roof is going to hang on that beam. The outside walls all have plenty of places to head off and bring the weight to the foundation.

My first guess is it will have to be steel -- but, it's amazing what they are doing today with structural wood. Naturally even one supports makes the whole building much easier .... having the whole this open would be really nice and I would at least price to see.


Good you are matching the house pitch -- that's what going to be most noticeable. High slop roof's are really nice visually.

 

[jchetty]

Trusses are best if you don’t ever plan to change them. If one lvl beam or a steel is too big, you can look at a flitch beam.

A flitch beam is more manageable. You take lvl and sandwich steel between them. Much thinner and way easier. You bolt them together in place. If you guys don’t watch This Old House and Ask This Old House, you can YouTube or use the PBS app. Amazing shows and a good way to try to keep current with new tech for plumbing, hvac, carpentry, and general home stuff.

 

[GMCGarage]

Are floor trusses used to create the entire floor support or are they used as a beam to hang perpendicular floor joists from?

Yes, floor trusses or TJI joists would span from front to back. DONT have a beam running the 38' length with columns.

You are looking at a 18" TJI depth for 16" oc. Thats with 40LL and 10DL, which is normal for a second floor.

 

[glentre]

bdbull,

As mentioned for my build, steel was the most expensive choice and would have resulted in a deep and exposed beam in the garage ceiling, getting in the way of my lifts. TJI engineered joists would have worked but on 24" centers and strong enough to carry a normal attic load, they would have been too deep also. Using smaller ones on 16" centers increased the cost over trusses. That is why the attic trusses were selected. I'm not an engineer but think that TJI's would be the way to go for you because trusses don't seem to be possible with the large front gable. You would then stick build the roof and front gable structure.

If you go with a 12/12 roof, you might want to look carefully at the proportions of the finished garage. You don't mention the height of your garage ceiling but ceiling height, roof pitch and amount of eave overhang will affect the exterior look. Since our two garages are so similar, let me know if photos of any view of my build can help you and I will PM them to you.

Be glad to give you any specific info you need regarding my construction but the plans are copywritten preventing me giving them to you. I can give you the contact info on the guy who designed my garage. For $750 he incorporated all my ideas, made several revisions until I approved the finals and gave me extensive plans good enough to submit and get approval from the local authorities and to get bids from several contractors.

PM me if I can help.

Glen

 

[Jackfre]

My shop is 30x34 with Attic Trusses. I have a 7x8' area in the center of the attic space for storage. Pardon me...light storage. No beams, no supports. Nice and clean. I think I'd go that way.

 

[matt_i]

Imo, attic trusses spanning the 30' are going to be the cheapest. I am not sure they make LVLs as long as you want, if so, its special order for sure.

Must have appropriate mods for staircase opening and also the dormer (unless its just for deco and is built on the outside of the trusses.)

I got an easy 12' wide space in 26' of 6:12 roof. Your roof looks more like a 12:12 and its going to be easier to get more room up there.

 

[rburke65]

I built a 32'x56', attic trusses 24" on center, 8:12 pitch. That gave me an attic space of 14' wide, 56' long and 7'.5' tall. Love it.

 

[bdbull]

Regarding trusses...I don't think we can do trusses because of the gable on the front. I don't know for certain, but I can't think of a way that trusses could support it. This image is the style we are going with.

 

[Radix2]

Just joined yesterday. Great forum with lots of great resources.

I'm in the planning stages of a new detached 30x38 3 car garage (see mockups here). The preliminary plans I've gotten so far call for a beam that spans the width (38') of the garage right down the middle. I'm assuming this will need to be some type of LVL beam to carry that large of a span, but I'm concerned about the placement. Currently it is called for it to rest over the large window on the left side of the structure. That doesn't seem wise to me...to put such a large beam over a window. 1) Should it be placed there and 2) if so, does the window header need to be sized differently than normal?

Thanks...this is my first of what is sure to be numerous posts on here.

First of all to answer your specific questions ..

1. you can...
2. yes! The header will have to be sized for the beam load, which will be about 1/4 of the entire roof load. Most likely you will need some extra framing all the way up on both sides of both windows (same issue on the first floor). You gotta get that load all the way down to the ground properly. Since the window is not wide, it will be manageable, but not the std window header. Look for multi ply and probably LVL from your designer.

Are you an engineer ? If so, you can download Forte from Weyerhaeuser to size LVLs, etc.

Depending on what exactly you are trying to do on that second floor, there is no reason that trusses would not work just fine. On my garage, I have trusses and a cross gable. Do you have some specific plan for a 2nd floor vaulted ceiling overall ? And want the vault to be 12/12 like the roof ? That is about the only reason I can think of that would require your framing.

Trusses could give you a upper floor with some vault and would be considerably less expensive. You could also use trusses for most of the roof and conventional framing only in the center, would give interesting ceiling design opportunities, simplify the (shorter) ridge beam and save $$.

 

[Radix2]

I missed your walkthrough of the upstairs... If you want it just like that, then you will need the ridge - but it does not have to carry a big load since you have floor joists, all you have is a conventional framed roof and the ridge board is not loaded.

I was assuming you had an open space down to the first floor and the need for a structural ridge beam as you described (implied).

It would still save a bit to use trusses due to construction time, but you would need to go to a panned ceiling and would need to narrow the space with some taller kneewalls - I don't like the style shown with tiny knee walls anyway, but that is a personal preference..

So, in summary, your original question is moot, there is no issue with the window, it will be std header since the loads will be carried by the rafters not the ridge.

 

[bdbull]

@Radix2

I don't necessarily need the second floor space exactly as it is in the walkthrough. That's just how Chief Architect designed it when I drew everything up. It's only for storage right now. I'd rather have trusses up there, but I'm just not sure how to tie them into the front gable. I wonder if I could even use trusses all the way across the horizontal and then build the front gable onto the trusses. The space would be pretty much unusable, but like I said it's only for storage anyway.

 

[firebirdparts]

You are going to have to decide if you want a full half story above or not with a normal floor rating. That will dictate a lot of it.

Your mockup does not appear to be tall enough for a lift. Are you planning for cars on a lift to intrude into the 2nd floor?

 

[bdbull]

You are going to have to decide if you want a full half story above or not with a normal floor rating. That will dictate a lot of it.

Your mockup does not appear to be tall enough for a lift. Are you planning for cars on a lift to intrude into the 2nd floor?

Yes, I want a full half story above with a normal floor rating. However, it will just be for storage. Gotta get stuff out of the basement so we can turn that storage space into livable space.

I'm not a car guy so no lifts. The garage will be for parking cars and storing tools and my kids' outside toys (bikes, scooters, etc.). Lawn equipment will be stored in here for a while, but the ultimate goal is to build a pole barn on the back of the property for all that stuff.

 

[Radix2]

@Radix2

I don't necessarily need the second floor space exactly as it is in the walkthrough. That's just how Chief Architect designed it when I drew everything up. It's only for storage right now. I'd rather have trusses up there, but I'm just not sure how to tie them into the front gable. I wonder if I could even use trusses all the way across the horizontal and then build the front gable onto the trusses. The space would be pretty much unusable, but like I said it's only for storage anyway.

Any real lumber yard with truss service can design and quote it with trusses for you. The gable can be built from trusses or layed on if you don't want full living space there.

If you look at new houses being built, even full hip roofs are built with trusses - just about every truss is different down the line to give the taper in two dimensions.

It will come down to the design of the inside space you want.

Do a cross section in CA and look at what the width and height might be in the attic for a storage truss - say 5-6 foot kneewalls, 8 foot ceiling in center. Then decide if you want to lay on the gable or make it a real dormer space. The truss guy can price it both ways and give some options.

 

[firebirdparts]

I think based on what you want, I would go with the original design. You will just get more space that way.

 

[The Tool Tyrant]

If you REALLY want storage, use truss joist for the floor system and conventionally stack the roof using a clear span ridge beam. This will allow you use of 100% of the upstairs floor space. The load on the ridge beam would need to be carried down to the foundation by means of posts and headers (if required). Headers are sized for carrying the load imposed on them and that's the job of the structural engineer.
This is not rocket science. Design what you want /need, then hand your plans to the structural engineer and he will spec what is required structurally to accommodate your dreams.

 

[Radix2]

Yes, I want a full half story above with a normal floor rating. However, it will just be for storage. Gotta get stuff out of the basement so we can turn that storage space into livable space.

I'm not a car guy so no lifts. The garage will be for parking cars and storing tools and my kids' outside toys (bikes, scooters, etc.). Lawn equipment will be stored in here for a while, but the ultimate goal is to build a pole barn on the back of the property for all that stuff.

Getting a full floor up there with a clear span is going to require TJIs for the 30' span. And that is at 16-19 in on center and 16" deep. So check your plans for height with that thick of floor. Also, your rafters are 21' long, and the valleys longer still, so unless you can find some decent really long lumber, you are looking at TJIs up there too. All this is a ton of labor to build, so if you conventionally frame it with TJIs make sure it is really what you are going for. TJIs in roof framing take a lot of extra work to connect and reinforce at the webs vs. std 2x lumber.

https://www.weyerhaeuser.com/application/files/9814/9500/1501/1488927548_TJ-4000.pdf

Do you have anything from the architect? Or are you looking to design it first yourself on CA then give it to a arch to finalize?

 

[bdbull]

Do you have anything from the architect? Or are you looking to design it first yourself on CA then give it to a arch to finalize?

I do not have anything from an architect yet. I designed it myself in CA just to get an idea of what it would look like visually. I'm no CA expert though, just someone who learned how to mock up a visual design. I did get a designer to draft it to scale, but that is where my questions have originated. I don't believe his plans are structurally sound so I was just looking to get opinions here on some possibilities. I fully plan on taking it to an architect, I was just trying to educate myself a little before I do. I'm the type of person who wants to fully understand whatever I'm talking about so I can make a more informed decision.

On that note, the information I have gotten from this thread so far has been extremely valuable, so thanks to everyone who has chimed in so far.

 

[bdbull]

Are you an engineer ? If so, you can download Forte from Weyerhaeuser to size LVLs, etc.

Yes...but not that kind. I'm a software engineer and only use a mac. It looks like their software only runs on Windows.

 

[firebirdparts]

30 foot long floor trusses and rafters could work. The original design could work. The original design with posts in the garage would work and be real strong. I think those are the 'good' options.

 

[kbs2244]

So, the argument seems to be ridge beam vs scissors truss.

Both will put the roof weight stress on the wall without the need for attic floor joist being stressed by anything other than the weight on the floor.
So no middle of the room posts.

The scissors truss will out the weight on the eve sides. That means your door wall will be loaded pretty well and you will need some strong over door headers. You will also lose some attic height to the lower chord of the truss.

The roof beam will put the weight stress on the gable ends. I would like to see the windows spaced so there can be a single post from foundation to roof peak. That will mean no windows centered on the gable end walls. Another advantage is the attic height goes up to the bottom of the rafters.

For the attic floor you have the same two choices. You can go with front to back trusses or a second beam from gable end to gable end. Full span floor trusses will need to be deep. So, you will lose height either at the car level or in the attic.

A second beam would mean two 15-foot spans vs a single 30 foot.
That will be much easier to handle and nowhere near as deep
.
In the end, my recommendation is the 2-centered beam way.
It avoids heavy weight stress on any headers and gives higher ceilings both downstairs and up.

The second story gable end post can be set on top of the attic floor beam.
The stress on it will be vertical only.
With well-planned sheathing placement to avoid any tendency to “knee out” you will be fine.

Find your local steel supplier and tell him your plans.
They all have a guy on staff that can run your numbers a tell you what you need for a “I” beam that long.

 

[GMCGarage]

Im lost here.

There is nothing magic about a 30' floor joist that also is used to resist push out from your rafters. Done all the time.

Spend 500$ and get it engineered and move on.

 

[kbs2244]

My argument against 30 foot joist would be the depth needed and the height lost.

 

[GMCGarage]

My argument against 30 foot joist would be the depth needed and the height lost.

thats the trade off instead of having a column line down the center.

Flip it 90 degrees and put in a steel beam and have 19'-0" spans.

I guess what I am saying these are not difficult engineering designs. Done daily.