Results 1 to 15 of 15

Thread: cutting birds mouth in roof rafter

  1. #1
    Join Date
    Nov 2005
    Location
    englewood, fl 90 miles south of Tampa
    Posts
    130

    cutting birds mouth in roof rafter

    I am building an 8x 10 shed for use as workshop for my daughter in CA following directions in book by david stiles. The roof will be a minor challenge. I am planning on 8 inch overhang on eaves and will add 8 inch overhang on gables for appearance. My question concerns cutting the bird mouth on rafter trusses so they sit squarely on wall.

    Daid Stiles says to cut smple 2x4 rafters at 66 inches with a plumb line at approx 40 degrees. He gives measurements as to where to cut birdsmouth but my attempts w jig saw left much to be desired. Here is my question. I have a workbench which is precisely 8 feet long and my shed will be precisely 8 feet wide. It seems to me that I can rough out the sample truss attaching the tops with a gusset and using a collar tie for rigidity and then just hold the sample truss ( with a helper) against my worktable to determine exactly where the birds mouth cut will go, trace it, cut it with a circular saw and my sample is complete. Looking for someone who has been there and done that to comment and set me straight. I think I will upgrade rafters to 2x6 to facilitate cuts w circular saw. Rafters and wall studs are 16" OC.. Wall studs are also 66 inches but the use of a collar tie 11 inches above wall height results in ample headroom in the shed

    Last question re sheathing and shingling roof. I am 70 and do not relish heights or climbing on a roof. Should I use roof jacks nailed into rafters for a secure place to sit while nailing sheathing and shingles. This will be my first roof ever. Can these roof jacks be rented or must i buy same

    thanks

  2. #2
    Join Date
    Jun 2007
    Location
    Pleasant Valley, New York
    Posts
    140
    try to give you an easy way out... if your ridge beam is up and walls????

    go to out side of wall and put up a 2 x 6 from were it should sit on ridge and wall and trace it then cut .. the angle on the ridge is what you need for the facia cut just need to figure out your 8" over hang. .... If you are running 2 x 6 only about a 2" birds mouth is needed. shed13.jpg

  3. #3
    Join Date
    Jan 2007
    Location
    New Hampshire
    Posts
    2,022
    I have local rental places that rent roof jacks. The other option they also have available is a man lift. A little pricey but not bad. You should be able to get away with the smallest. It will help with laying the first several courses (I'm unnerved having my behind higher than my head at the edge of shear drop), plus you can use it to haul the singles to the roof. Have you looked at a metal roof? I put one on my open-side shed. The roof framing has to be more square (less room for error) but goes up quick and easy, and uses furring strips instead of heavier plywood.

  4. #4
    Buy a genuine Swanson Speed Square. Look at the little blue book that comes with it. It has tables to help you lay out both length and cuts. Remember that the bottom plates and top plates are the same width apart. Without sheathing on the building. you can use the end wall and bottom plates to do your lay out. Beats the heck out of trying this up on a ladder. We usually gang rafters together with a clamp. Then we cut the vertical cut with saw set to match the pitch of the roof. Then we unclamp them, lay them on their sides and do other cut with circular saw up to cut to lay out line. Then use jig saw to finish cut.

  5. #5
    Join Date
    Nov 2005
    Location
    englewood, fl 90 miles south of Tampa
    Posts
    130

    birds mouth cut......no ridge beam

    I intend to make roof trusses and then screw them to yop rail

  6. #6
    Join Date
    Nov 2005
    Location
    englewood, fl 90 miles south of Tampa
    Posts
    130
    anthony

    i might consider a metal roof. No snow where i am building near SF. The roof rafters are only 66". Can you get metal roofing cutom cut at a reasonable price? I am building my first shed following tips in a book. It says to extend shingles 1/2 inch beyond facia board, would metal roof go on the same way? For a small roof like I am contemplating, it would seem to me that I could get by using an 8' foot step ladder and working left to right. Roof peak is about 10 feet off the ground

    i definitely will look at tool rental places and I share your enthusiasm for heights. I am 70, have taken 2 falls and don't want to take a 3rd one

  7. #7
    Join Date
    Nov 2005
    Location
    englewood, fl 90 miles south of Tampa
    Posts
    130

    birds mouth cut

    [Qbruce,

    thanks for your suggestions. I will buy speed square and get the book. I can picture what you mean re cutting the vertical line parallel to plumb line. I am using 2x6 for rafter. Should I make that cut about 2 inches long?

    UOTE=Bruce Wrenn;1815879]Buy a genuine Swanson Speed Square. Look at the little blue book that comes with it. It has tables to help you lay out both length and cuts. Remember that the bottom plates and top plates are the same width apart. Without sheathing on the building. you can use the end wall and bottom plates to do your lay out. Beats the heck out of trying this up on a ladder. We usually gang rafters together with a clamp. Then we cut the vertical cut with saw set to match the pitch of the roof. Then we unclamp them, lay them on their sides and do other cut with circular saw up to cut to lay out line. Then use jig saw to finish cut.[/QUOTE]

  8. #8
    Join Date
    Aug 2008
    Location
    Los Chavez, New Mexico
    Posts
    618
    Blog Entries
    1
    A real builders supply.. not the big orange type, should be able to order custom cut metal roofing to any length you want (just make sure you get your measurements right!) It's easy to install. when ordering the roofing don't forget something for the peak and drip cap for the bottom and sides.. looks much better. You can get plastic or wood that fits under the roofing to seal it up from insects, etc.

  9. #9
    Quote Originally Posted by tom coleman View Post
    . I have a workbench which is precisely 8 feet long and my shed will be precisely 8 feet wide. It seems to me that I can rough out the sample truss attaching the tops with a gusset and using a collar tie for rigidity and then just hold the sample truss ( with a helper) against my worktable to determine exactly where the birds mouth cut will go, trace it, cut it with a circular saw and my sample is complete. Looking for someone who has been there and done that to comment and set me straight. I think I will upgrade rafters to 2x6 to facilitate cuts w circular saw.

    Last question re sheathing and shingling roof. I am 70 and do not relish heights or climbing on a roof. Should I use roof jacks nailed into rafters for a secure place to sit while nailing sheathing and shingles. This will be my first roof ever. Can these roof jacks be rented or must i buy same

    thanks
    laying out on your bench or sheet of plywood should work
    also you can tack your rafter to the wall to make the pattern

    I would make a ridge beam and get rid of the collar ties all together...


    what pitch is the roof?

    if it is less than 5" you dont need anything and since it is only 8' you can do most of it from a ladder
    Carpe Lignum

  10. #10
    Join Date
    Sep 2006
    Location
    Milwaukee, WI
    Posts
    5,384
    Couldn't you just cut a pieceo of two-by as long as your top plates are apart, and use this to make your cut marks on the ground?

  11. #11
    Join Date
    Feb 2003
    Location
    Lafayette, IN
    Posts
    3,737
    I wouldn't screw those trusses to the top plate--toe-nail them. Most off-the-shelf screws are not structurally rated and are too brittle for the types of movement and loads that trusses see. If you want to screw them down, you can get Simpson Strong Tie truss straps that screw to the side of the truss and the face of the stud below (they have a quarter-twist in them).

    I second the advice to get a Swanson speed square (and it's included framing manual).
    Jason

    "Don't get stuck on stupid." --Lt. Gen. Russel Honore


  12. #12
    Join Date
    Jan 2007
    Location
    New Hampshire
    Posts
    2,022
    You can cut the metal roofing with a metal cutting blade on a skil-saw (with hearing protection) buy laying a 1x4 across the high spots. If you make the poor mans skil-saw straight edge with the board along the edge for saw to guide against, it goes real fast. Typical lengths are 8' and 12' (96" and 144") 66" x 2 = 132", so a 12 footer could be easily cut in two and only lose less than 1' of material. Unless you are lucky enough to find someone that will/can sell the custom size at a reasonable price. I was not so fortunate, so I made the rafters long enough to accept an 8' piece of roofing (something like a 14" over hang, but it does help move the snow away from the edge)

  13. #13
    Bird's mouths are usually the length of the width of the top plate.

  14. #14
    Join Date
    Feb 2010
    Location
    Middle Earth MD
    Posts
    332
    Use your bench or better yet build your floor deck and make up your trusses on the deck before putting up the walls.
    For layout, using the "step off" method is as simple a method as any, just need a carpenter's square and a set of stair gauges.
    No need to account for the ridge thickness with trusses.
    Cut one "rafter" precisely and use it for a pattern to mark out the rest.
    Skill saw the cuts and use a jig or hand saw the clean out the birdsmouth.

    Lay down the first truss members on the deck, tack blocking to the deck to keep the parts aligned as you apply the gussets and you'll be able to put out a batch in no time.

  15. #15
    I cut my rafters to fit the top plate of the wall, if you have sheathing on wall, make the horizontal cut 4", so when you push it up against the wall it fits the top plate. Drill the holes in the rafter with your cordless drill, but drive in 16d nails. Might keep you from splitting your rafter out.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •