Is my attic floor over my garage strong enough to use it for storage and maybe as a small work area?

Question

I would like to use the attic space above my 2-car garage for storage of items around the house and garage, and if possible, utilize some of the space as a small work area. The previous owners left the space with some randomly placed pieces of particle board and other flat wood (including an old door!) over the joists to aid with walking around up there. I want to put down some consistent thickness plywood or good quality particle (fiber) board as flooring.

But first, I need to make sure that what I have is strong enough, and if not, get some good ideas on how to strengthen it adequately. I would like to get some expert advice regarding this.

I have included a set of photos that have text in them to help explain my situation and my questions. Thinking that strengthening is a good idea, I included some ideas I have for that, explained in the photos. I would like to know if my proposal is adequate to strengthen the floor sufficiently.

Please review what I've shown and explained and give me your feedback. It would be greatly appreciated!

After posting my questions and original photos, Chileab Construction gave me some great feedback and asked some good questions. Based on what I've learned I am proposing to add a steel H-beam across the span of my attic space in order to strengthen/stiffen the floor. Chileab asked about the load bearing points for the beam, so I took some additional pictures and created a couple of sketches (first sketch without the beam; second sketch with the proposed beam added) to help show this. I am looking forward to what Chileab Construction thinks about this idea (and others who might want to comment).

I read David French's question and I would like to answer him here. David asked how I attached the joists to the underside of the steel beam. What I did was use pieces of heavy gauge steel L-brackets that I bought at a local home improvement store (Menards). I used two L-brackets per joist, one at each side of the steel beam. It's been over 3 years now since I worked on this, but I believe I remember that I used 3/8" carriage bolts to attach each L-bracket to the joist (two carriage bolts per L-bracket). I used a washer under each nut, between the nut and the L-bracket. I believe I used locking nuts. For attaching the top of each L-bracket to the bottom flange of the steel H-beam I decided to create a "sandwich" type of joint using strips of fairly heavy weld steel "straps" (I think 1/8" thick), that I also bought at the home improvement store, along with a stack of thick washers. I used a heavy high grade steel 1/2" bolt to run through each L-bracket, the washer stack, and the steel strap. The result was a joint formed by clamping the edge of the beam flange between the steel strap and the L-bracket, with the stack of washers there to symmetrically load the bolt (distribute the clamp load across the washers and the beam flange edge, and not allow the edge of the beam flange to try to slip out). This is kind of hard to explain, so I will include some pictures that I took back at the time to hopefully help you see what I'm talking about. Something to note is that I had to grind off a good amount of each washer so that I could keep the 1/2" bolt close to the edge of the beam flange for best strength of the joint. (Each stack of washers thickness equaled the thickness of the beam flange.)

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Answer 1

You have 2x6 joists 16" o.c. and lets assume #2 fir- the MAXIMUM spam (where they are supported underneath - bearing the weight) for a 20 lb dead load is 9'10" and for 10 lb dead load: 13' 2"
You show 11' +- in photo but it is unclear if there is support at that point. you can check span table at: https://www.awc.org/pdf/codes-standards/publications/wfcm/AWC-WFCM2018-ViewOnly-1711.pdf

There is some interesting framing in that attic: The 2x4 at the peak of the triangle which is set on top of the ceiling joists is very odd, in my opinion. It is transferring a load from the roof to the ceiling, and unless there is a wall underneath: you probobly have a bow in the ceiling at that point below.

Soooo: minimal storage, depending upon support at the 11' 3/4" point - Once you put a floor downs there even with the intentions of keeping it light up there - people forget in time.. . . .

As to the beefing up the joists with 2x8s that is an option - but the total span is more important. Is the entire width unsupported? and if so what is that total span?