Another Rafter Question

[JRC3]

I bought a house with a 24x24 garage. It was built in 1983 and the neighbor told me it was built by the homeowner with no permits and such (her father was involved so she knows). They've "webbed" the rafter ties to the rafters. The actual roof does sag and they had car parts and junk up there. Seems to me that tying the two together just puts weight on the rafters that should not be there. Even if it's just the dead weight of the rafter ties and 1/2" decking and not even considering the stored items. Should I remove those "webs" "queen studs"...Whatever they should be called??? The rafters and rafter ties are 2x6. Seems like somebody was trying to overkill the design and did more bad than good. Attic is roughly 6' so it's a 6/12 pitch.

I'd like to use the space for some light storage. Seems to me I could add extra 2x6 so they would be spaced at 12" instead of the existing 24". Going bigger than 2x6 isn't really an option I want to explore.

Sorry for the mess, it was even worse, I'm in the process of cleaning it out.

 

[Falcon67]

I can see where that would put the floor load on the rafters - rather than really "supporting" the floor as was probably the intention. Lots of weight would tend to pull the whole thing closer to the floor.

2x6 joists (rafter tie at plate level) are not really sufficient for a 24' span. 2x10 is more like it. 2x6 rafter for a 12' rafter span is in the ballpark. My joists are 2x12 over 24' because that's all they had. I could just about store a whole car up there, those 2x12s don't have much give LOL.

My old shop used 2x6 over a 20' span. With a lot of misc parts stored over them they sagged about 1" over 8~10 years.

 

[lakeroadster]

My thoughts:

The best thing to do:
Have a truss / rafter designer review the existing structure, based on it's current geometry and the required environmental loading for your location.

The next best thing to do:
Remove the decking and add the correct sized 2x? based on whatever weight you want to support, then replace the decking. This should help: http://www.southernpine.com/span-tables/joists-rafters/

Don't sister anything to the existing ceiling joists.

Don't change the existing rafters or vertical ties.

 

[oldmxracer]

In the second picture what is all the dark wood on the left hand side of Your ridge board ?

Right hand side looks good but the left side ?

Think, I would also like to see some collar ties !

 

[PassnThru]

Well - that looks familiar but without the plywood gussets. My garage was built that way - it's a poor mans truss. Here is my experience with that.
I had my 24X32 built by a prefab company - I'm lost for the name right now. They used 2X6 ties and rafters on 24 centers although the walls were on 16. They used lengths of 2X4 to tie the rafters to the ties. I thought it looked weak and noticed that the ties were sagging with no weight. I went with rafters to have storage so that was unacceptable. Not to mention the fact that they were supposed to hold up my garage doors and openers. And it was adequate for that - but barely. It didn't fit my plans for storage. So before I finished the inside, removed those ties and I put a 4X4 post slightly off center to the rear of the garage. I then put 2X12s up in the attic above the ties front to rear on the 32 foot length. They had a 3.5 inch space between them - they were attached to the post and then the ties were attached to them with cripples. Basically a beam that is above the ties/ceiling joists instead of below. I then reattached the questionable hangers you have but further out to allow more floor space.
That was 14 years ago - my roof looks great and my ceiling doesn't sag.
A friend at work had the same company build the same size garage within months of me - he put a heavy desk in the top to utilize the space as an office. The company rep (local contractor) put in stairs for him and what he called a 'strongback' which was basically just two 2X4s joined on an angle. The first thing I noticed was how bowed his roof was.
If you want storage up there, you need to reinforce in a way that doesn't put extra stress on your rafters. That may mean a post in your garage - yeah I know - we all hate them. They can be placed strategically though.
However, at this point, if the roof is already sagging then you probably will never get it back straight without rebuilding it.

 

[ard]

So the rafters are 2x6 and span (approx) 12 ft, from ridge to wall?

I think that will be too small...what is your snow load requirements in OH? Your local bldg may publish that on their website.

Then we have the 'floor', aka 'garage ceiling'?? What is that made from? Those span 24 feet, yes? A2x6 will not span that for a ceiling, let along adding plywood AND walking on it.

 

[The Tool Tyrant]

You're already pushing the limit on your rafters. Here in San Diego, a #2 DF rafter @ 24" o/c will span 11'-9" with 'lightweight roofing' and 10'-2" with tile...and of course NO snow load in San Diego.

I can't tell what the species of lumber is...kind of looks like southern pine, but not sure and if so, it has less carrying capacity than D.F.
Personally, I would forget about storage, unless you want to invest some real money by installing a 3.5"x 5.5" (minimum) parallam beam between each 2x6 ceiling joist and still that would only be for very light storage.

The ridge should always be the next size larger (2x8 in your case) than the rafters tieing into it, this is minimum and would include a ceiling joist at plate height at each set of rafters to create the required triangle, which keeps the bearing walls from spreading apart and the ridge from dropping.

At this point, I would remove the plywood from the ceiling joist and remove the vertical 2X4's tieing the C/J to the rafters. If the rafters themselves are bowed down, you would need to jack each one up at the center of their span and sister another 2x6 to them. Make a full seat cut on one 'sample' rafter (minus overhang) and ridge plumb cut. See if you can get it into place without too much issue, if it's a pain, shorten the birdsmouth cut until you can install it without too much issue. Nail the new rafters into the existing with 16 sinkers at 12"o/c staggered.

As long as there is a C/J tieing each set of rafters together, the undersized ridge board won't be an issue.

Take your time, be safe and it will all be good.

 

[kbs2244]

Do you any actual sag somewhere?

They were trying to hang the floor load from the rafters instead of supporting it from below.

If you are going to keep the load light, I would just leave it as is and use it.