Attic framing upgrade?

[rlmartinson]

I am working on upgrading the framing to make the attic space above my garage into usable space. The original plan was to just do enough to allow for light duty storage, but now I figure if I go through the work/expense I may as well build it strong enough for living/work space in the future.

We bought the house about 3 years ago and the (22'x23') attached garage is on the north side of the house and has a 12/12 pitch. The attic space has no flooring with open framing (not rafters) of 2x6's with 24" spacing that are probably 14' long and overlapped about 5'. There is a vertical piece that connects the horizontal 2x6's to the ridge board. The ceiling height is great at about 10.5' and I have replace the opener with a jackshaft model.

I started sister-ing more 2x6's onto the existing and this is helping but probably not enough. They are cut to but up to the end of the opposite 2x6. I am also planning to put up knee walls (2x4's) about 3' from the walls and I will run them long and hang down into the garage space to be used for additional storage in the upper corners. I figure this should stiffen everything up by reducing the span length. I have some 1/2 plywood to use for flooring.

I was talking this thru with a friend of a friend and he suggested sister-ing a 2x8 onto the 2x6's and centering this 2x8 in the span to reinforce the splices. Does this make sense? I assume that I should make it flush with the bottom and set it on top of the walls like the other 2x6's?
I could make it flush on the top and then the plywood flooring would span 20' instead of 24" but it would not fit on top of the walls and would need joist hangers and notches? I seem to have analysis paralysis.

Other plans are to install a subpanel so my air compressor can get to full pressure and add a 240V outlet from old Hobart BetaMIG welder. I also hope to build elevator to help move items into the attic.

 

[firebirdparts]

Does this make sense?

No, it really doesn't. You can't span 22 feet with junk like this. There's no vertical depth, even with a 2 by 8, and no matter how much stuff you scab on, it'll be weak as a kitten. It's certainly possible to hang some weight from the roof, and that's what you have now. I am not sure really how to evaluate how much you can hang there. Attachments would certainly need to be very sound. I guess it's not "wrong" to try to suspend a bunch of weight on a board (the 2 x 8) by hanging it right in the middle, but it's not a common thing to do.

So I-joists, floor trusses, and putting posts down to the floor would all be an improvement here and be easy to make sense of. In fact you could take out that vertical row of connections in the middle.

 

[John McA]

Whew! Determining an appropriate design involves documenting what you have in terms of the existing structure condition/age and, what you want to add to the existing Dead Load and, what you want to have in terms of the New Live Loads. What is an acceptable Deflection ratio? L/240 is pretty bouncy. Is 1 inch ok with you?

Have sister-ed (reinforced) a private flat roof carport spanning 24 ft to create a 500 sf roof deck. No snow loads. The decisions for the detailing, spacing of the added elements were carefully considered along with existing conditions, were permitted and, exceeded Code. Project completed in 1982, functions and still meets the current code.

After reading the previous poster comments - please, be safe? I've seen my share of human mousetraps built and standing, just waiting for the final straw, quake or other event to send occupants to their graves. A few permitted projects too! Please do your diligence. I suggest a trip to Building and Safety for some fact finding. Assumed this is not a 3yr old house. Existing plans may even show up perhaps?

Good Luck,
John McA

 

[billconner]

I second Firebirdparts comments. What you have now is not in my opinion even code compliant.

I'll assume the ridge board is a ridge board and not a ridge beam. A picture would help verify this.

Your best option is replace 2x6 rafter ties with TJIs, probably 14" deep - need to consider spacing and connections and bearing.

Second best is add a beam level with top plate - probably a 12" range LVL - under ridge, with a column in each gable wall and one in center on new footing. Now you can probably replace 2x6s with 2x8s (Maybev2x10s - need more info) and floor it.

I don't know what your plans for access are but if this habital space - anything other than storage - 5/8" drywall on garage ceiling and a way out not through garage.

 

[G-rex]

You are asking for trouble IMO. For reference, when I had my new 26x26 garage built, I had the attic trusses designed for 40psf loading because I intended to use it for heavy storage and didn't want to worry about it. The bottom chords are 2x10s @ 24" spacing with 2x6 bracing throughout on the wings. You are just throwing bad to worse if you keep up with this line of thought.

 

[NUTTSGT]

You're not going to span 22'-23' and 24" OC with tradition 2x lumber without a support beam down the center.

 

[jar944]

14" i joists would clear span but you would only have a 10 psf dead load with 24" centers.

 

[Hank11]

You need to hire an engineer.

 

[John McA]

^This

 

[jar944]

You need to hire an engineer.

Good luck finding one to return an email or phone call on a sub 7 figure job.

 

[duneslider]

14" i joists would clear span but you would only have a 10 psf dead load with 24" centers.

No reason he has to stay at 24" oc. I have 12" i-joists in my house at about 19.5' and am over L/720. It was cheaper for me to do 12" i-joist on 12" centers than 14" i-joists on 16" centers. I'm not gonna go to the trouble of looking up the i-joist charts but I am sure you could get L/280 or better with 12" joists at 22' and for a space above a garage I think that would be acceptable.

Scabbing dimensional lumber together is a recipe for disaster and not gonna work. Probably multiple ways to skin this cat.

 

[firebirdparts]

Right. 24" centers not happening, obviously. That should have not been needed to be pointed out. It's 22 feet across (or 23, maybe).

I forgot to mention, you can get a very respectable load with 2x12 on 12" at that distance also. I can't buy 22 foot 2 by 12 lumber anymore around here as far as I know.

 

[dcg9381]

You need to hire an engineer.

You probably won't get one for this type of job, but various suppliers on line have calculators for buying LVLs based on spans.. And you can reference span tables for lumber limits.

 

[billconner]

Right. 24" centers not happening, obviously. That should have not been needed to be pointed out. It's 22 feet across (or 23, maybe).

I forgot to mention, you can get a very respectable load with 2x12 on 12" at that distance also. I can't buy 22 foot 2 by 12 lumber anymore around here as far as I know.

I think you'd have to be in select structural grade, maybe no. 1 in a few species, but would work. Lifting the suckers up there, I'd wished I'd gone TJIs.

 

[kbs2244]

steel I beam down the center will shorten the span

 

[NUTTSGT]

Right. 24" centers not happening, obviously. That should have not been needed to be pointed out. It's 22 feet across (or 23, maybe).

I forgot to mention, you can get a very respectable load with 2x12 on 12" at that distance also. I can't buy 22 foot 2 by 12 lumber anymore around here as far as I know.

One thing we don't know for sure is the place the OP is measuring at. Is he measuring in side the walls and not the outside where the joists will sit ?

Menard's list #2 (not SYP) 2x12x 24 at about $120 each and special order. It looks like I-joists would be his best bet for a clear span but I think it will cause another problem. Once you start adding height to the joists, it may impact the roof line and create a whole other issue.

 

[rlmartinson]

Sorry for the delay guys, I will get some pics and more accurate dimensions this weekend. Rest assured whatever I do to upgrade will be better than the current setup and I will not use the space for something it will not support. I try to overbuild when I can.

The house was built in the mid 80's and did not have the best carpenters. There are a lot of squeaky subfloors, out of square doors, and sad drywall finishes. Apparently they forgot to compact the backfill next to the house before the garage slab was poured. It settled a lot and is a future problem to fix.

I like the idea of a steel I-beam down the center, because then I could add a trolley and 500-1000 lb. chain fall for future projects. But it would be bad to add a center post in the middle of my garage.

 

[Showkey]

No comment on the engineering of this solution……..the lumber is available, special order in some areas.
Got a feeling $2300 for joists is not in the current budget ?

2x12-22’ are $98 each

 

[Zeke]

steel I beam down the center will shorten the span

Not enough info but on the right track. In the center below the existing spliced joists which now are little more than rafter ties. An engineered I beam will do the same, cost less and be lighter to install. The other option is to reinforce the ridge, but a lot more trouble. Both require some work at the ends.

A full on engineer would certainly handle this well, but a good framer with span charts can do this.

 

[My Old Tools]

I like the idea of a steel I-beam down the center, because then I could add a trolley and 500-1000 lb. chain fall for future projects. <b>But it would be bad to add a center post in the middle of my garage.</B>

Center beam does nothing for you unless it is supported on each end by posts going to foundation.

 

[billconner]

Center beam does nothing for you unless it is supported on each end by posts going to foundation.

which may need to be enlarged under columns.

 

[jar944]

Center beam does nothing for you unless it is supported on each end by posts going to foundation.

Unless you also add front and rear beams to carry the load out to the walls (with appropriate additional support and foundation upgrades)

Certainly the more $ route.

 

[billconner]

I guess if one double or two single doors is a key.

Each column is supporting around 6000-6500 pounds probably so depending on soil, around 2' x 2' footing each column. Ballpark.