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Joining roof lines

PlaneWood | Posted in General Discussion on March 25, 2003 11:26am

I’m adding onto the back of my detached garage.  Due to easement restrictions, the add-on will have to set at 50 degrees to the existing garage.  No other option feasible.

The garage is 21′ wide at the back (slab dimension) with an 18″ eve overhang all around with 8″ rough cedar facia boards.  The stand alone garage has an asphalt shingle hip roof all around with a 12/6 pitch.  The add-on will have to be about 16′ wide (do the math).

When I draw an overhead plat of the roof design, the facia boards don’t break on the same lines that the two roof’s make.  The add-on roof will have to have about an 8/5 pitch to properly join.

How do you handle this problem?????   See the A—A’ line in the attached drawing

PlaneWood by Mike_in_Katy (maker of fine sawdust!)
PlaneWood

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  1. hasbeen | Mar 26, 2003 01:49am | #1

    I think you're right, this ones tricky. 

    Given the constraints you have to work with, I don't think you can have both matching slope and matching roof line without cutting away part of the existing garage so that you can split the 50 degree angle equally, rather than having all of the angled part in the new addition. 

    Is there any way that you can move the back wall of the addition a couple of feet farther back?  (Maybe a variance?)  If you could do that, then instead of cutting away part of the existing garage you could extend the back wall of the existing garage (only on the back side) so that you could split the angle equally and have an even hip.

    I hope somebody else comes up with a better idea and a better way of explaining it!

    Good luck!

    It doesn't matter how fast you get there, it just matters that you go in the right direction.

  2. woodroe | Mar 26, 2003 02:41am | #2

    You need to change the wall height of the addition to make the facia line up. Truss heel height change is another option.

  3. Piffin | Mar 26, 2003 02:54am | #3

    Your variables are plate height, roof pitch, hip angle of tie-in, and overhang.

    You'll have to play around and dtermine wjhich of these will need to be compromised to line up.

    .

    Excellence is its own reward!

  4. User avater
    BossHog | Mar 26, 2003 03:20am | #4

    Got some dimensions, or a .DXF file?

    I do this sort of thing all the time with trusses & trying to match stuff up. Something somewhere along the line will have to be adjusted to match everything up, but it's doable.

    Nonconformists are all alike.

  5. User avater
    Timuhler | Mar 26, 2003 03:41am | #5

    PlaneWood,

    Looks like fun.  If I understand you correctly, your ridge height (without any HAP) for the 6-12 garage roof is 63" (10'6" unadjusted rafter run).  Your add-on is 16' wide, so 8' is the run of the rafter (unadjusted) .  8' run and a 63" rise make a 7 7/8-12.  If you went with unequal overhangs then your overhang on the 7 7/8-12 would be 13 11/16" (if you have equal HAP or heelstands for both pitches).  Your cheek cuts on the 6-12 side would be 37.30° ( 56.70° saw angle because your saw tilts from 90°).  On the 7 7/8 -12, the angles would be 56.70° (on the saw 37.30°)  The plumb cut ont the hip/valley would be 21.69° or 4 3/4-12 ( I think if it was me, then I would just leave it. 

    If you choose to make the overhangs equal, then you have to raise the plates on the add-on.  It doens't look that great if you have open soffits to do it this way because you'll have more wall under the add-on.

    For equal overhangs you have to figure everything from the fascia line.  Starting from the overhang (18") plus the run of the rafters (10'6" in the garage) at a 6-12 gives you 6' of rise (no HAP or heelstand).  The run of the rafter for the addition is 8' +18" or 9'-6".  That makes a 7 9/16-12.  You would have to add plates or adjust your HAP or heelstand 2 3/8".  This would give you equal overhangs.  The hip would then slide offcenter by 4 11/16".  The valley offset would be 3 3/4"  The cheek cuts for the jacks would be 38.43° on the 6-12 side (but saw tilt would be 51.57°on the saw)  and 51.57° (but 38.43° on the saw).  The plumb cut on your hips and valleys would be 21.39° or 4 11/16-12

    I probably made some mistakes in the numbers there.  I'm hungry and tired :-)  Anyway, even if there are some mistakes, you have an idea what's invovled.

    You will get a lot of answers if you post this question over at Joe Fusco's forum.  http://www.josephfusco.org/phpbb/index.php  a lot of roof framers frequent that area and can do a better job than me at giving you some numbers and advice. 



    Edited 3/25/2003 9:03:07 PM ET by TIMUHLER

    1. PlaneWood | Mar 26, 2003 04:16am | #6

      Wow!  Talk about assistance!!!!

      Would the simpliest thing be to just reduce the soffit overhang on the add-on??  That would change the roof pitch all around it, but that would be fine.  I want the facia line and the top of the roof to be the same as the garage.

      Thanks everyone for the help!

      PlaneWood by Mike_in_Katy (maker of fine sawdust!)PlaneWood

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