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-   -   What is safe span of two 2x12's? (http://www.diychatroom.com/f19/what-safe-span-two-2x12s-194688/)

jackmel 01-24-2014 02:16 PM

What is safe span of two 2x12's?
 
I have a friend with a cracked-ceiling problem. He had a metal roof installed and added solar panels on top. Not sure if they removed the old seal-tab roof before installing metal roof.

The living room, dining room, hall and kitchen are developing cracks in the ceiling. Looks bad. I check the attic. Looks like those pre-formed A-frame roofs with those metal mesh sheets connecting the rafters and joices. However, there is no load-bearing wall holding up everything between dining and living room. It's a large, 30' or so unsupported span. I think the problem is the roof has become too heavy. Be up to me I'd remove the solar panels and if there's seal-tab below the metal roof, remove everything down to the decking and put a new roof on it. Lot of work though.

How about if we install two 2x12's 12 foot across from one side of the wall to the other. I think it's about 12 feet. May be just 10' or so. Haven't measured it yet. It's a single-story, ranch-style home.

What would be the maximum span for 2x12's in this situation?

Ok Thanks,
Jack

tony.g 01-24-2014 05:15 PM

Difficult to say without pics, but from your description I suspect your friend has more problems with his roof than can be solved by a couple of 2 x 12s.

AndyGump 01-24-2014 08:05 PM

I believe what you are describing on your friend's roof system is a truss system.
Do not want to muck about with that without having a truss engineering company look into it.

Andy.

jackmel 01-25-2014 06:59 AM

Outstanding guys. I believe you are both on top of your game. I didn't feel like installing the beam anyway and I've been thinking about it since shortly after Tony posted. Yes, I need to do the right thing: suggest to my friend to contact a building inspector or truss engineer to assess the problem.

jackmel 01-25-2014 07:35 AM

In the interest of helping others, apparently less qualified than me, I wish to confess about something I did that I regret doing:

This is my ex-wife and she lives in the house and I just felt sorry for her with all the cracks in her ceiling so I offered to patch the cracks for nothing. I'm really very good with sheetrock and already floated them about three times until it finally dawned on me: YOU'RE HIDING A SERIOUS STRUCTURAL PROBLEM JACK!

I really regret doing this as I've been a remodeler for over 30 years. I've decided of course to tell her I won't finish the work; I wish to leave the remnants of all the cracks the outlines of which are floated nicely, so that they can be reminded of the underlying structural problem so that they will address it correctly as I stated above.

Ok, I'm done.
Jack

joecaption 01-25-2014 07:42 AM

Is she also trying to use that attic for storage?
Was there supporting walls there at one time and someone removed them to open up the area?

jackmel 01-25-2014 07:54 AM

Quote:

Originally Posted by joecaption (Post 1296387)
Is she also trying to use that attic for storage?
Was there supporting walls there at one time and someone removed them to open up the area?

There is no storage in the attic.

Ok Joe, you're just getting me in more trouble: About 35 years ago, I removed part of a connecting wall and installed cabinets on the partial wall and a counter top. And in my defense, I recommended to her dad to put a 4x4 column at the end of the counter top. He did not. I believe although I'm not sure, small cracks did eventually appear in the ceiling next to the partial wall. But I do not recall them ever being serious cracks until to the best of my knowledge, about 3 or so years ago.

Now, they installed the metal roof and then the solar panels which are very nearly directly overhead of the cracks. I'm pretty sure the cracks became more noticeable near about this time.

The cracks were pretty serious before I floated them. I've not yet gone on the roof or looked at it carefully to see if the roof is sagging.

Edit: I guess I should point out the way someone good with sheetrock would have handled this problem would have been first to fix the underlying structural problem, remove all the cracked sheetrock, install new, re-float the entire ceiling until all traces of the renovation vanishes.

I failed in that regard but I'm not doing all that work for free.

Olcrazy1 01-25-2014 10:13 PM

If it was my ex I'd tell her to make her bedroom right under the area and that everything looks perfect! Seriously sounds like major structural issues need addressing.

sixeightten 01-25-2014 11:01 PM

What do those solar panels weigh? Generally a roof truss is designed to carry the roof weight as well as a snow load. If those panels are heavy, that certainly could be the problem. Unless there is something weird going on, I highly doubt that those roof trusses had any bearing other than the exterior walls. Just because there was a wall under the middle at one time does not mean it was a bearing wall.

jackmel 01-26-2014 03:21 PM

Hey guys,

The area in question is approx. 12x30 or so but I haven't measured it. It's a long, un-supported span with the truss roofing going length-wise across the 30' span. There doesn't seem to be diagonal cross-beams between the rafters and joices. I invited a family-member architect to look at the problem (I'm not bad myself to solve it either). He feels that if we just add the diagonal braces between rafter and joices as well as put a center support from ridge to ceiling (three braces per 24' width so about six sets of these using 2x4's then we should be alright and that's fine with me since putting a beam there is a bit unsightly and really hard work if any of you have done something like that, that is do it well I mean.

I'll first shore it up along damaged area so we don't fall through. May crack work I already did but I'm good at sheetrock so no problem.

Ok, then that's the plan: me and my brother-sort-in-law, Thursday first thing. about 6-8 hours (may also put an L-shaped 2x6 member across center along 12' span. Full day's work. I told him he's making $1000.00 on the deal.

Also: he has 9 solar panels each seems to be 2x6. Don't know how much they weigh but architect said not an unacceptable load on roof. Rather the solar panels are equivalent to storage in attic and there is not storage in this attic.

Gary Evans 01-28-2014 07:46 AM

You need to send us pictures.

This may not be a quick fix and what is the rafter spacing ?

Are these 2x12 rafters, scissor trusses or another type ?

depending on the snow load, 30' may be too long a span for 2x12 rafters at ANY spacing .......12", 16" or 24"
If you have no snow load rating requirement then 12" on center should be alright.
Or if there on 24" centers you could double up every rafter.

jackmel 01-28-2014 08:16 AM

Quote:

Originally Posted by Gary Evans (Post 1297879)
You need to send us pictures.

This may not be a quick fix and what is the rafter spacing ?

Are these 2x12 rafters, scissor trusses or another type ?

depending on the snow load, 30' may be too long a span for 2x12 rafters at ANY spacing .......12", 16" or 24"
If you have no snow load rating requirement then 12" on center should be alright.
Or if there on 24" centers you could double up every rafter.

The problem with a picture is that I've already floated the cracks nicely so won't see much.

I live in Louisiana so no snow load. Rafter spacing is 24" although don't recall definitely if they're 2x6's. Nothing bigger I'm sure.

The plan is for me to first just look at it. I can crawl safely right up to it over the hallway. Look at it and decide how much effort to put all those braces. May not be enough head-height and I think there is a large AC duct right down the middle where one would normaly place a vertical brace from roof ridge down to ceiling joices so will have to just offset a pair say 2' from center on each side of the duct work.

If it looks doable, then the plan is to adequately shore up the ceiling span (12'), then go up and affix the reinforcement. Too crowded I think for two people. I'll have someone on the floor though to help me.

Personally, if this was my house, I would add the braces and a beam.

sixeightten 01-28-2014 08:26 AM

Upon further reading, is it possible that when you removed the wall, you accidentally cut through one of the trusses? Even a small kerf could significantly weaken the whole truss system.

JKeefe 01-28-2014 02:43 PM

Quote:

Originally Posted by jackmel (Post 1297076)
the solar panels are equivalent to storage in attic and there is not storage in this attic.

My understanding of roof trusses was that, if they are in place, attic storage is not permitted; the attic floor is not engineered to support any additional weight beyond the roof plus a saftey factor.


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