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-   -   Stick Rafter not attached to bottom chord & sagging, new Trusses (http://www.diychatroom.com/f9/stick-rafter-not-attached-bottom-chord-sagging-new-trusses-55201/)

Robear 10-14-2009 11:40 PM

Stick Rafter not attached to bottom chord & sagging, new Trusses
 
I have an older bungalow with "A" frame stick rafters (32 ft total span ..16 ft ridge centers) that are sagging and pushing one wall out about 2". The roof sheating has been removed to jack up the rafters and then the plan was to install webbing into the stick rafters...BUT the stick rafters are off center from the ceiling chords by about 4"!! NOT sure what to do.

There is an interior load carrying wall that runs along rafter ridge (16ft in the middle of the rafers)...could one attach a "Y" webbing from the plate of the inside carrying wall out towards the middle of the top cord on the rafters? HELP the sheating is off and weather is not good. :(

jogr 10-15-2009 10:07 AM

First a little scolding. Did the rafters move 4" to the side after you removed the sheathing? Of course not, they were always that way. So why would you have ripped off your roof knowing that your plan of repair would not work? And if you did not know ahead of time the structural details before you started then you certainly shouldn't have started the project. Seems like once a week or so someone posts on here that they have ripped into a project full speed a head and end up in a real mess/crisis because they didn't know how they were going to perform a critical step before they started. I know you don't need to hear this now but am posting this to remind others who might read this thread the importance of planning ahead rather than ripping into something before planning.

At this point your best bet is probably to upsize the rafters. You'll get a straighter roof than unbending sagging rafters that will fight you and you won't need to worry about webs. The span isn't that big (12' from outside wall to center interior load bearing wall, right?) and you should be able to get the correct rafter size from the appropriate IRC table. Chances are it will be 2x10 but depending on the details and lumber grade available 2x8 might work. Get really good quality straight lumber. Surprisingly, around here the Lowes currently carries really nice straight Douglas Fir that is graded #2 or better and about 1/3 of the bundle actually grades out at #1.

If you can't find the correct IRC table your building department might even be able to help if you have one that doesn't mind DIYers. Mine is very helpful.

Robear 10-15-2009 11:49 AM

Stick Rafter not attached to bottom chord & sagging
 
With pain I agree that one needs to know what the roof structural details are before starting ...and know what the ramifications are. Yep the bottom cord was not attached to the stick rafter...so we can no longer jack up to eliminate bows in the "A" stick rafters and insert webbing between the bottom and top cords.

There is talk of placing a large "Y" support ...from a plate on top of the loadcarrying wall which runs under the ridge of the stick rafters ....to the mid section of the upper cord. The Y support would have a long span and would not be as strong as a fabricated truss

It seems that replacing with new engineered/fabicated truss rafters on a roof that is actually spans 32 ft spans (16ft centers) on a low pitch is a preferred going forward solution.... HOWEVER ..it seems a contractor has a problem with getting a overhang beyond the exterior wall with any new truss given the current pitch...so he is talking about attaching overhang to the new fabricated/clipped truss by notchng into the 2 by 4. I am vulnerable and in a crisis! ( my roof is open and tarped...it is raining...and the full truss solution is not known .) :huh:

Scuba_Dave 10-15-2009 01:07 PM

Do you have any pictures?
What size are the roof rafters? 2x6 or x8 or x10 ??
How far apart are the rafters ?
16" OC you need 2x8's as a bare min, my last house I used 2x10's
Are there any collar ties installed ?
Where are you located ? Snow load?
Is a contractor doing this work ?

Robear 10-15-2009 03:00 PM

Stick Rafter not attached to bottom chord & sagging - replace with new fab truss?
 
Here is some of the facts:
  • Lumber Size of existing stick rafters?: 2x4 lumber
  • Spacing of existing stick rafters ? ~16" apart ?
  • Collar tie on exising stick rafters: A nailed collar tie exist on the upper portion of the top chords.
  • Rafter Span: Total 32 ft
  • Load: There is significant snow load here.
  • For info...there is a load carrying wall under the center (16 ft) or ridge of the rafters.
Questions:
  1. What lumber size is required for the new fabricated 32 ft span truss? Do I need 2X4 or 2X6 lumber for the pre-fabricated truss??
  2. Roofer has a problem for the new proposed fabricated truss to provide the overhang beyond the exterior walls...can't get beyond the wall plates..so plan to tie in the required overhang for my existing fascia by attaching through a notching process into the 2X4 fabricated truss's. ?

Robear 10-15-2009 08:40 PM

Determing correct replacement truss
 
TWO QUESTIONS:
  1. The plan is to get 10 new 2X4 fabricated truss for a roof that has a truss span of 32 ft (end to end) and a roof length of 25 ft. There is a load carrying wall down the ridge of the rafters at 16ft; and thre is snow load here. QUESTION: Do I need 2X8 fabricated truss for this application???
  2. Also roofer has a problem for the new proposed fabricated truss to provide the overhang beyond the existing exterior walls...can't get beyond the wall plates..so he plans to tie in the required overhang for my existing fascia by attaching through a notching process into the 2X4 fabricated truss's. ? Sound ok?

Scuba_Dave 10-15-2009 08:46 PM

You are going to use a 25' truss on a 32' span??

What?

A truss is an engineered design
They need to be designed for the specific load & installation
Nothing sounds OK

Robear 10-16-2009 10:51 AM

Truss Determination
 
The total truss span will 32 ft (end to end) and the roof length is 25 ft.

Question: What size of lumber is required for a 32 ft fabricated truss span on a low pitch bungalow with snow load: (2X4 or 2X6 lumber ) ?

12penny 10-16-2009 12:07 PM

robear...never would have thought to ask that question on a DIY forum. Trusses are engineered and they take all variables into account when you order them. Ask the people supplying your trusses.

I'd GUESS 2x6.:wink:

Scuba_Dave 10-16-2009 12:14 PM

Sorry.....misread

But trusses are engineered
They need to be built based on designs for the load you have
Any notching or cutting allowed will be specified in the engineer report/design
Usually NO modification is allowed to a truss

There is no guessing on this

jogr 10-16-2009 05:23 PM

If you are going with prefabricated trusses the the truss company will actually determine the lumber size.

I'm having difficulty figuring out why the trusses cannot extend past the wall plates. What is in the way? Can you post photos? Is your concern how to get the overhang at the gable end? For that you would order dropped truss for the end walls. They are made shorter so that you can extend a 2x4 out across the tops. Your truss designer does this all the time. Talk to him and he'll walk you through it. Ask him a gazillian questions.

Never ever notch into trusses unless the truss designer/engineer oks it.

BTW placing trusses on an existing ceiling with wires, ceiling joists, ductwork etc can be very difficult. I'm not sure why you can't just go with new rafters. Seems far easier.

Your contractor seems like the wrong choice for this job. His original plan of adding webs would probably just make your ceiling joists sag too. He seems to be way over his head. Can you find someone else... quick.

jogr 10-16-2009 05:36 PM

Robear - when you say trusses do you really mean rafters? Are you just talking only about the top chord that goes from the top of the wall to the ridge of the roof that the roof sheathing is nailed to? That's a rafter.

The IRC has a table for sizing rafters. They definitely won't be 2x4 or 2x6 for a 16' span (your rafter span would be from the center to the wall so 16'). I'm guessing a 2x10 or 2x12 but you need to get it from the IRC table or an engineer.

If your "roofer" doesn't know how to do a gable end overhang you need to get someone else. I hope you didn't hire a shingle slammer for this job. You need a real framer. A real framer could put new rafters (with overhang) on a simple gable roof and sheath it in one day.

I

Scuba_Dave 10-16-2009 05:41 PM

2 threads on the same subject have been merged


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