Preliminary Framing Design

[jpballer84]

Guys,

I just joined the Garage Journal with the hopes of getting some advice on my new garage design. I am an Engineer In Training in Louisiana and I work as a Naval Architect, so I am extremely familiar with the engineering principals that are envolved in designing structures. My short fall for this project is that I don't have experience with framing houses specifically.

I'm planning on using my empty backyard to build a new 23' x 24' gable roof garage. I did the plans in AutoCAD down to the nailing patterns and tiedowns and I've recently submitted them to the parish for review. I'm waiting to hear back from them, but I have a feeling that they are going to gripe about something and I want to get some opinions from experienced people (y'all).

Basically, I framed the garage so that I have a large upstairs "bonus" space so my joists are going to have some live load across a 12' wide sheathed portion which I am calling the "bonus space". The issue that I'm concerned about is that my joists do not attached to my rafters at the side walls. I used balloon framing so the joists sit atop a ledger in the wall studs and the wall studs continue up another 2' to the top plate where my rafters land.

I'm aware that the rafters try to push out the upper 2' of wall but that is why I used balloon framing so that the load path is continuous and there isn't a joint that needs to be stiffened. In addition, I am also using collar ties on each rafter. The collars are very high (which isn't as effective), but they need to be for me to have the clear open bonus space.

The wood frame construction manual and all rafter/joist span tables assume something different than what I am laying out, but I think that my layout and sizes that I call out are going to be adequate.

Anyway, I've attached the first page of my ACAD plans to illustrate the above. I'd appreciate any and all feedback on any glaring issues that I might be overlooking.
Thanks in advance,
Justin

 

[swedevil]

Welcome - I'm still getting started out and learning here myself, so I can't really offer any advice on the ACAD.. What part of LA, being a Naval Architect, I'd assume JRB down in New Orleans, but who knows...

 

[51rider]

Nice drawings.
You might want to consider the jointing detail on the collars. Since you are using them as structural members, you will need to specify the fixing method. It is unlkely that nailing will be acceptable. You will probably have to use a threaded rod, M12 or M13 should suffice with a toothed timber jointing washer between rafter & collar with a square washers on the face of each assembly. Depending upon preference, a spring washer may also be used to lock the nut in place or you could use ny-loc nuts. The nuts may need to be tightened to a specific torque too.

I'm not an engineer but that was what I ended up having to do when installing collars in my house loft. bear in mind that I am on the other side of the pond & your regulations will be different!

Good luck with it!

 

[jpballer84]

I work for Elliott Bay Design Group down here in New Orleans. Our corporate office is in Seattle but I'm home grown in Louisiana.

51 Rider - Okay, thanks for the input. That makes sense since I will be delegating those members to carry more load.

 

[DougB442]

you should have a double sill plate, and the bottom member should be a piece of pressure treated lumber.

you need a termite sheild.

Calculate the moment load at the collar tie to rafter, I don't think your rafter size is adequate based on your span.

you didn't say where you were located. did you account for wind and snow loading appropriate for your area?

most places don't allow open framing anymore, and you must sheetrock the inside of the garage. if this is the case you must account for the extra dead load on the framing members.

Will this be heated? if so, you need insulation, and most local building dept's require a 'Comcheck'.

you might be required to install sheathing clips if you're in a high wind, tornado, or hurricane zone.

why are you using such a large foundation grade beam? won't a spread footing suffice?

Is there a frost line you need to worry about for the grade beam?

where are the anchor bolts for the sill plate?

you need to show the compacted gravel and vapor barrier below the slab. also insulation if it's heated...

Are you in a Seizmic zone that would require extra shear loading and support?

where's you stair handrail?

where's your support columns for the 2nd floor girder? size?

header schedule?

nailing schedule?

window schedule?

after a quick glance...

edit:
I don't think your connection detail is such a good idea for the intermediate let-in. your shear loading will most likely be too much for those 2x4's, you might need to re-think that

 

[ddawg16]

JB....welcome....and I feel your pain....

I pretty much did the same thing you did....2 story garage with the second floor being open...I have a ridge beam that goes down the depth of the roof so that supports the roof.

Send me an email address and I'll send you a copy of the Los Angeles County Building Code as it relates to houses/garages.....even though it's LA...it's based on UBC which almost everyone follows..

You can see my build in the link in my sig.

 

[jpballer84]

ddawg16 --- That would be great man! My email address is [email protected]

I appreciate the help!

 

[jpballer84]

DougB442 -

Again, I'm located in a surrounding parish of New Orleans, Louisiana. I am in a category B wind zone of 130 mph.

As I said initially, I only included 1 of the 4 pages to my plans. Many of the details you mention exist on the other sheets. I see what you mean about the sill plates, termite shield


My rafters and joists pass the requirements in the span tables and the wind loading criteria, but my main concern is the 2' offset between where the rafter connects to the wall and where the joist connects to the wall.

Do you think that the parish is really going to require that I insullate and sheetrock my 500 square foot detached garage?? I was hoping not, but I guess I'll find out soon.

The garage won't be heated. I'm using an 18"x12" concrete foundation beam because my soil capacity requires it. No frost line issues down here. The sheathing attachment & sill plate bolts are on other sheets. Not in a seizmic area either. I didn't draw in my stair handrail. The center girder is sized so that it can span the lenght of the garage. No support columns required. Headers and Nailing are on other sheets too. I'm comfortable with all that stuff.

I suppose that instead of letting in the 2x6 into the wall studs I can just screw the 2x6 directly to it and then my joists and bear on it. I was thinking the 'let-in' would be cleaner though.

Still though, my main concern is whether or not I can have the arrangement shown where the joists aren't attached to the rafters. If that isn't allowed, I can't think of a good way to get the open space other than having a huge ridge beam (which I'm not too crazy about because of the issues with construction).

Thanks for the advice and help.....

 

[boobag]

do you have a height restriction to deal with?
the 8' ceiling is awefully low for a garage.
are you planning on parking a vehicle in there? looks like only one car will fit.
will there be a post supporting the middle of the 2nd floor girder?
place a door or window next to the garage door, so that it looks like there was a reason for the door not being centered.

 

[jpballer84]

The maximum mean roof height is 14ft. I'm right at the limit.

Actually, I'm planning on parking two of my full size f150's in there, which by my measurements will fit with 1' clearance on each side and between them. It is a "double" car garage door. 16'x7'. I sure hope a car can fit in there, haha!

Again, there will not be a post supporting the girder, it was sized to span the full length.

The reason that the garage door is offset is to line up with my existing driveway.

 

[DougB442]

I think you should just platform frame it, and instead of using joist hangers on the floor joists, set the joists atop of the main girder. less hardware=cheaper material cost. this way you don't need to worry about the moment and shear forces on the exterior wall at the connection point

 

[APEowner]

Since snow load isn't really an issue where you are I think you're probably OK but what about a couple of steel rod/turnbuckle assemblies to handle the spreading loads?

 

[kbs2244]

I hope you are a small man if you think you can get out of an F150 parked one foot away from a wall or another truck.

I would say you need 30 to 36 inchs min.

Go to a praking lot or find a fence and try it out.

 

[Wingnut65]

Nice plans and nice project.

I'm not convinced the plate you show will give the uplift that you will need. I'm not familiar with the codes in your area, but in Fla, we need a strap that extends over the top of the rafter down the other side.

One other suggestion on the footing detail... The siding should extend below the top of the slab to keep water out. Right now, there is no amount of caulk available to keep your garage dry. Try sliding the footing inward to have the sill plates at the edge of the footing/slab. Using J-bolts embedded in the slab pour will be the best anchoring you can get.

Good luck on your project.

 

[jpballer84]

If I rest the joists atop the girder instead of using hangers, then I'll be reducing my clear opening height by the depth of the joists, which I wouldn't want. What is 'platform framming'?

As for parking two trucks....I said 1 foot but that is acutally 1 foot past the mirrors on each side which is still really tight, but that would only happen when I go out of town or something or never at all. I think if i needed to squeeze it in, i could though. Either way, thats what I'm stuck with so hopefully it works out.

I see what you're saying about the siding & footing. Thats just my lack of experience showing. I know nothing of siding. Needless to say, I'll be learning a lot on this project. One question though, if you cement J-bolts into the slab, how do your drill your sill plate holes so that everything will line up when you stand the wall up? I assume you make the wall on level ground and then just stand it up over the j-bolts, but I can't think of a way to drill the sill plate perfectly so that the wall lands flush and level. Whats the method for doing that?

Thanks again and please keep it coming!

 

[WNYflyer]

Since you are in a high wind area of 130 mph versus the most of the country at 90 mph you essential have 2 times the wind load most peoples have.

That being said, be careful of the effects of wind suction on the leeward wall as well as the leeward section of the roof. The large suctions may cause compression due to bending on the faces of the wall studs and rafters not braced by your roof and wall sheeting. Because of this you may have to provide blocking to tie the rafters and wall studs to the roof and wall sheeting to properly brace them.

Also looks like you are coping the floor joist at the garage door header. Make sure you have enough meat left in the floor joist for shear. You may need to run some floor sheeting from North to South wall to act as a diaphragm for wind in the East/West direction. And of course all the floor sheeting tied into the sidewall framing/sheeted shear walls for proper load path to the ground.

 

[Black Moon]

Not much headroom under the girder.

The grade outside has to be more than 2" below finished floor. Locally it's 8" but you'll have to check local code.

You really want to go larger all the way around unless you have a square footage limit.

No way you'll get 2 trucks in there. It's too small plus you have a workbench and staircase in the way.

All other comments above are excellent.

 

[numbah9]

Does anyone here have the ability to draw a framing plan like the OP did? I need to submit some plans to my town for permit approval. My father-in-law is going to be doing the work, but he won't do the drawings - he's old and grumpy

Just a standard 20x20 garage, trusses, 2x6 construction.

 

[p_mori7]

For 7' high garage door, you need 9' ceiling.

23x24 is too small for 2 full size F150's. 26 x 28 would be better.

Screwing ledger boards to the 2x4 studs is not ideal for supporting 2nd story floor joists, screws have low shear capacity compared to nails.

A truss company can design trusses to fit your span & storage room.

I would build the wall to 9', then incorparate the knee wall inside the truss, giving you a tensioned bottom chord, and no center girder.

I would run the stairs in an "L" to lessen intrusion on garage floor space.

Original post says 23x24, but plan shows 22' x 22'9"... always exclude the eaves from your area calculations.

 

[p_mori7]

One question though, if you cement J-bolts into the slab, how do your drill your sill plate holes so that everything will line up when you stand the wall up? I assume you make the wall on level ground and then just stand it up over the j-bolts, but I can't think of a way to drill the sill plate perfectly so that the wall lands flush and level. Whats the method for doing that?

Thanks again and please keep it coming!

Take the pressure treated bottom sill "before you assemble the wall", place it over the exposed bolts, tap it with a hammer over every bolt...that will leave a mark showing you where to drill once the wall is assembled...drill the holes larger than the bolts to allow for adjusting...use a large thick washer before securing with the nut.

Always assemble your wall on the finished floor of the garage... it will be flat and level enough.