sagging roof structure-how to support


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Old 01-19-06, 09:18 AM
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sagging roof structure-how to support

My house was built 60 years ago by my grandfather, who was not a skilled carpenter (or plumber, or electrician...). Needless to say, it has problems. One of the most serious problems I'm trying to rectify now is the sagging roof structure. The house is a single-level concrete block ranch-style on slab (in Arizona). It has a low-pitched (not sure of exact pitch) hip roof constructed completed from 2x4's. It is supported by 2x4 struts that rest on 2x4 joists NOT on top of bearing walls (or any walls for that matter). This has caused serious deflection and failure (breaking) of the ceiling joists resulting in roof and ceiling sag. I plan to replace the ceiling joists with up-to-code materials, and I would like to support the rafters to avoid having to rebuild the entire roof. The only way I can think to support the rafters is to install struts that will rest on the new joists. However, from what I've read struts must be aligned with a bearing wall, which is a problem for me because the struts necessary to support the roof would for the most part not align with any bearing walls in the house, of which there are few. My question is: Is there any way I can securely rest the struts on suitably-sized joists without having them directly above a bearing wall? Thanks for any input!
 
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Old 01-19-06, 09:22 AM
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Rebuild the roof. Advantages are:

1. It will be easier to work on the ceiling joists.
2. You might live through the repair without the ceiling and roof coming down on your head.

Staying out of the hospital will save more than the cost of the roof materials.
 
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Old 01-19-06, 11:27 AM
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The problems with rebuilding the roof are:
1. I live in the house and do not have alternative living quarters during such an undertaking.
2. I don't have the money to replace the entire roof structure + roofing + etc, etc. As it is, I'm working on one room at a time to do my remodeling/repairs.

Any other suggestions?
 
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Old 01-19-06, 06:50 PM
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Up To Code

Well, you said you wanted to repair the roof with up-to-date and code compliant materials (and methods I presume) and the only way to do that is to go to the expense and extent of removing the roof system and replacing it with a properly code compliant system.

Doing it piecemeal and one room at a time isn't going to work.

IBM5081 is absolutely correct.

The roof has to go and there are no alternatives.

You could not even be issued a building permit for your plan...

So start saving your pennies so you can do it right.
 
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Old 01-19-06, 08:18 PM
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This is Arizona, not Washington. Why do you need a roof:

- To keep out rain
- To keep out dust, dirt, etc.
- To provide shade
- To retain heating/cooling

Surely there are seasons where you cannot do without a roof; but there are also seasons when you could make do with some plastic for a while. I don't know what deed restrictions or city ordinances apply in your area. Check with the city building permit folks to see what type of on-site temporary shelter is permitted while you work on the house.
With a little help, it should not take more than 1 week to re-frame the walls, ceiling joists and rafters. Insulation, decking, felt and shingles should also be less than 1 week. I take it that the structure is not very large, 1800 square feet or less with a simple gable roof, if it was constructed using the methods and materials described. I assume that there is no garage space or it is included under the roof for the house.
 
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Old 01-20-06, 05:58 AM
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Just one slight correction to manhattan42, I wanted to use up-to-code joists and supports *without* replacing the entire roof, which excludes the rafters , sheathing, and roofing. This may sound ridiculous, but read on.

Anyway, I understand that to have a properly constructed roof, mine would need to be entirely replaced. However, the fact remains that doing so, even on my 1200 sq ft house would be beyond my financial means (I would have to hire contractors), and would be almost equivalent to rebuilding the entire house. And truthfully, given my neighborhood and property value, it would be hard to justify the outlay of funds. The truth of the matter is that the roof has remained fairly solid (that is, it doesn't appear to be on the brink of collapse) for 60+ years in its sagging state, and I'm fairly confident that it can be bolstered to last at least another 60 years using a better supporting structure. I'm know that there are situations in which local authorities allow variances from code due to extenuating circumstances. I would hope that my case would be eligible for such variances. Given these conditions, assuming that there is no way that the entire roof will be replaced, can anyone suggest a suitable joist size and support mechanism that will at least keep the roof from sagging any further? Thanks for all of your help!
 

Last edited by bizillcizole; 01-20-06 at 06:27 AM. Reason: add detail
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Old 01-20-06, 06:57 AM
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It's a matter of roof support, not ceiling support. The law of gravity will prevail. Somehow, the weight of the roof structure must be carried. Since most roofs have a slope (or pitch), the vertical load is carried by the walls, the horizontal load is carried by the ceiling joists to keep the walls from pushing out from the centerline of the ridge.
You may end up with a wall of posts down the center of each room. There must be a transfer of roof load from those 2x4 struts to posts that connect the ridge beams to the ground (not the floor). It will likely involve pouring concrete footings as well as jacking up the ridge beam a bit. That wall of posts will become the load-bearing wall of the house. You may be able to reduce the number of posts by adding beams between the post tops under the ridge beam. We're talking lalley columns made from steel here, they're just at ground level rather than in the basement as would be the case in Pennsylvania.
 
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Old 01-20-06, 08:22 AM
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I do understand that the normal function of ceiling joists with respect to the roof is to prevent spreading, but I was hoping there could be a way to size the joists in a way similar to floor joists so as to be able to support the roof structure. Of course I would have suitable support for the joists using beams and posts as necessary. I imagine the difference between a static dead load whose downward force is concentrated in small areas versus a live load that is not so concentrated or static would be the main problem with my theory. But in contrast to the manner in which the structure is currently assembled, almost anything would be significantly better.

I don't know if this clarifies the situation any, but the roof is a simple hip-type on a more-or-less square floorplan. There is one ridge rafter about 15 ft long (if I remember correctly) and there is a bearing wall that runs *almost* directly underneath. All ceiling joists rest on the exterior walls and the single bearing wall. Get this: the longest span of these 2x4 joists is over 14"! And while directly supporting the roof at the same time!

Thanks again for your input!
 
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Old 01-20-06, 08:30 AM
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Originally Posted by bizillcizole
Just one slight correction to manhattan42, I wanted to use up-to-code joists and supports *without* replacing the entire roof, which excludes the rafters , sheathing, and roofing. This may sound ridiculous, but read on.

Anyway, I understand that to have a properly constructed roof, mine would need to be entirely replaced. However, the fact remains that doing so, even on my 1200 sq ft house would be beyond my financial means (I would have to hire contractors), and would be almost equivalent to rebuilding the entire house. And truthfully, given my neighborhood and property value, it would be hard to justify the outlay of funds. The truth of the matter is that the roof has remained fairly solid (that is, it doesn't appear to be on the brink of collapse) for 60+ years in its sagging state, and I'm fairly confident that it can be bolstered to last at least another 60 years using a better supporting structure. I'm know that there are situations in which local authorities allow variances from code due to extenuating circumstances. I would hope that my case would be eligible for such variances. Given these conditions, assuming that there is no way that the entire roof will be replaced, can anyone suggest a suitable joist size and support mechanism that will at least keep the roof from sagging any further? Thanks for all of your help!

Look, you've been given great advice so far and everyone is trying to help you so that you don't tackle this MAJOR project blindfolded. I'm a framing contractor for 22 years and what you have to do is a MAJOR Job and it's NOT a Do It Yourself JOB.

No one here can help you with your house without seeing it. It's that simple.

Can your house be done without removing your existing rafters, yes, but there's a lot of work involved buy doing so. You can remove all your ceilings and you would have to build temporary walls or beams going from the floor all the way to the bottom of your rafters and then nail braces to your outside walls to the temp walls. Then put your new ceiling joists in.

Or you can take out one ceiling joist at a time and install a new ceiling joist and then brace back down from the existing sagging rafters to the new joist.

There's many more options but someone would need to look at your house. This is a very dangerous project to take on. I by no means would tell anyone how to spend their money but when it comes to a structural problem like this, you either leave it alone if your saying it's been the same way for 60 years and hasn’t moved or you at least pay for an Architect or an Engineer to come over and look at your house.

This is what I do for a living every day so your project wouldn't be difficult to do because I have the man power to do it. For you it's not a little small addition off the back of your house that you can frame. This is your ROOF your talking about that if not done professionally can fall down on you and kill you.


Joe Carola
 
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Old 01-20-06, 08:58 AM
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Thanks, Joe, for your honest input. Your suggestions are along the lines of what I was thinking I could do. FYI, I don't doubt that the advice I've been given so far has been sound and that the instructions haven't been the right thing to do. I guess I'm trying to pull a rabbit out of this messed up hat of a house. I agree that consulting an engineer would be a good thing to do. How much could I count on paying an engineer for a short-term consultation?
 
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Old 01-21-06, 08:35 AM
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An engineer will usually run about $500 for a simple consultation.

And an engineer could also come up with ideas that could provide for having cantilevered ceiling girders that would be able to bear the loads of a roof placed on them at the ends by rafters, or tho have the ceiling joists redesigned as bearing girders using glulams or such to which you might be able to brace the existing rafters.

But these options would be expensive and could easily cost more than the simple demolition of the roof with new trusses reinstalled.

Some local box stores around here sell standard 4:12 slope gable roof trusses 26-28 feet long for less than $40 each.

Demolition and replacement doesn't have to be anymore expensive than an legitimate engineering 'fix'.

By the way I have LIVED in Arizona and as the old song says, "it never rains in Arizona. Man, it POURS!"...so let's not think rain is not a concern here.
 
 

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