Roof Rebuild

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Old 01-18-21, 05:15 AM
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Roof Rebuild

The picture shows a home addition I'm in the middle of. I want to tie the new addition roof all the way in to the peak instead to gain a higher slope. Pretty sure it's close to a 2/12 now. Also pretty sure this is a truss system. Can just the right side of the peak be rebuilt? The garage attic this is attached to is partial living space and partially not. The section of roof I'm rebuilding ties in to the non living attic space. The roof sections is about 10ft wide (across where the gutter would be).How much work is this? Estimated costs for Indianapolis?


 
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Old 01-18-21, 05:57 AM
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Go into the attic and see what type a roof you have. If you have trusses you cannot support a new roof on your existing without having the engineering reviewed by a professional. That goes for your current roof and re-doing it to the peak.
 
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Old 01-18-21, 06:17 AM
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I had a similar situation on the back of my house although I don't have trusses. I ran rafters from the ridge beam to the exterior wall along with supports at the original exterior wall. That was about 25 yrs ago. It can be done with trusses but additional support will likely be needed, a structural engineer would advise you on that.
 

Last edited by marksr; 01-18-21 at 07:07 AM. Reason: fix typo
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Old 01-18-21, 07:01 AM
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Yea, it's truss. Here is a picture or 2 from inside. I don't even see a ridge beam. Does a truss not have one?
this doesn't look promising...


 
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Old 01-18-21, 07:05 AM
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I posted some better pictures of the inside.
 
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Old 01-18-21, 07:07 AM
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Unlike stick built roof framing a truss system doesn't have a ridge beam. An engineer will tell you what needs to be done to change that roof pitch .... and is normally required by the permit office.
 
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Old 01-18-21, 07:10 AM
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As they say, things like that usually need an engineers' stamp of approval because it is putting a point load on the trusses that could possibly exceed the designed load of the trusses.

That being said, since the roof area is small it may not be a problem, provided you don't have some enormous snow load potential like they might in Buffalo, NY. But you would still want your plan approved by your local building inspector or it may be a problem when you sell the house.

You would need to strip the shingles off that side, then new rafters can simply be cut to match the roof pitch, and would be placed directly on the sheathing above the existing rafters. 2x12 blocking could be added between the trusses on that side of the ridge to give more surface area to toenail. And since you have 24" centers you would want to sheath it with a minimum of 5/8"... if you use 1/2" you would need to use h-clips.

that roof is too flat for shingles, and willl probably leak, right?
 
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Old 01-18-21, 07:14 AM
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Yes, that is why I want to change the pitch. I want to rebuild to the peak. Trying to figure out how much work that is.
 
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Old 01-18-21, 07:42 AM
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xsleeper, I was thinking the truss work under the current sheathing would need considerable work. Are you saying I could remove shingles to the peak, and build new rafters from on top of sheathing down to the new exterior wall? Then, possibly support inside the old truss network to make sure?

Obviously, I will need to get this inspected and checked out. I was just trying to get my mind around the scope of work. The previous attic is likely not supported for living space, and the new attic wouldn't be either.
 
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Old 01-18-21, 07:57 AM
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Yes, that would be the plan you propose to your building dept. They will tell you if you need to get it designed and approved by an engineer first.

But yes, the proposed plan would be to get up next to the peak inside and put 2x12 blocking flat against the bottom of the sheathing on one side of the peak. It would be fastened between the trusses. Then the new rafters would get an angle cut on them, and you would nail the tip of the new rafter straight down into the existing truss (the new rafters would be directly above the existing ones). And then you would also toenail the top of the new rafter to the 2x12 blocking.

Other than the blocking, you would not add any additional support to the trusses, that is not how trusses work. Trusses can either handle the load or they cannot.
 
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Old 01-18-21, 08:53 AM
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The minute you say "trusses" or "engineered" your local inspections dept. is essentially shut out. They are not trained or permitted to approve changes to Engineered structures.

I have trusses all over my house. During constructions there were trusses made wrong or something installed incorrectly. Each instance required a review and sign off by the Professional Engineer (it's capitalized for a reason). Luckily all that engineering was included in the cost of my trusses and the fixes they approved were simple and easy to implement so it was minimal impact.

To do anything now would require hiring a Professional Engineer. Last time prices started at about $500 and in the Engineer's travel time & expenses for two site visits. One at the beginning to inspect the current structure even though I have full copies of my construction drawings and all the truss engineering. Then another visit near completion to insure that the changes were made according to the Engineer's plan. My local inspections dept had very little to do with it other than insure I had the proper engineering done and that I did what the engineer told me.

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The thing with trusses is they are designed to only carry the designed loads. They are made with smaller lumber and are reinforced in only the areas that need it. With ordinary stick built construction adding a dormer is pretty straightforward but in my house you should see the truss work to make it happen. It is totally different with big scissor beams carrying the load over to doubled up, enlarged trusses to reinforced sections of wall... What you are doing is placing a new roof's load, in a narrow line on top of trusses not designed to carry a heavy load at that point.
 
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Old 01-18-21, 04:00 PM
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Update:

I forgot this architectural plan was approved by my county before work was done. As long as we adjust the work to plan... We should be good.


 
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Old 01-18-21, 04:14 PM
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Your plan shows a 2x4 knee wall built on top of the existing (former) exterior wall. (Center of photo marked easte elevation) That would cut the rafter span in half and greatly reduce the new load on the trusses.
 
 

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