Fast No Measure Birds Mouth Notch with Speed Square No Math How To DIY

I tried to make the quickest video on this topic possible. How to cut a correct birds mouth for rafters using a speed square and with no need of measuring. Mark both sides of the rafter first then cut both, make 1 master and then just copy the notch onto all of your other rafters.

[Reecegk]

all good as long as the rafter is sat above the ridge the same amount as your taking off your birdsmouth so it all comes down together, otherwise it will alter the pitch of the roof

[torchiertorchier]

I've watched 2492 videos, most with advanced algebra, trigonometry, and astrophysics on how to cut a birdsmouth. Thank you for this very human explanation!

[tutubi]

Pythagoras, Diophantus and Euclid would be proud of the dozen or so mathematicians of this topic on youtube. The millions of finger-counters are proud of this guy. Thanks a bunch, mate, you made my day!

[jacobkoder]

You'd have to raise your rafter at the ridge the same amount as the height you're removing for your birds mouth. This becomes more evident as you move up to 2x8, 10, 12 and/or your pitch increases.

The lower the pitch and smaller the lumber the more you can get away with the method in the video. It does not scale well though.

[El_Migz]

Just as I'm going to start the roof of my kid's playhouse, I get this gem!

Thank you 👍🏼

[ohiofarmer]

So as a guy who is seventy and worked in construction from age sixteen, just lay the rafters out on the floor full size and place a scrap piece for the ridge.. Build your roof frame directly on the floor before erecting the walls with all cuts checked for fit.
That's for you guys. I just use a framing square because there are unit length tables on it for common hip and Valley rafters. I could cut an entire frame on the ground and it will fit perfectly unless I make a mistake, but a quick check fixes all that. Probably the mistakes that would most often result in a poor fit is rafter length not matching the roof angle. Stick with a five inch rise per foot run and the length of the rafter hypotenuse is exactly thirteen inches per foot and then deduct one half the ridge thickness. On a ten foot wide building the rafter length is half the width which is five times thirteen or sixty five inches less half the ridge thickness or sixty four an a quarter for a 1.5 inch ridge

[roystephens]

I used this technique today on the rafters on my shed. Worked perfectly! Thanks for the video!

[randymelder]

I'm building a lean-to shed today with a very shallow pitch roof and put this to the test. Totally works! Thank you.

[Ash-cyyw]

The guy hijacking your awesome little video, , posting all the algebra, is the exact reason we all love your video so much. As someone else said, we aren't building houses in the Hamptons, we're just weekend warriors trying to do a bit of DIY. I'm building a lean-to garden shed and I thank you for this cheat !

[georgemckenzie]

Ideally you would show that the plumb cut at the top of crafter is being clamped in place above the ridge an equal verticals distance to the material removed at the seat cut allowing the rafters to settle equally at top and seat.
Way easier to make a tail template, and cut it on the stack, only lifting it once.

[TelecasterRon]

Nope, not correct. The scribe will kinda fit. But in fact once the rafter is set down the plumb cut is short. The level cut is no longer on the same plain. Also the birds mouth is to shallow. The plumb cut also opens at the ridge. Measure from the peak on the ridge board to the outside edge of the wall top plate. You will see that it is shorter than the actual dimension. Not a put down but A²+B²=C² (run x run + rise x rise = C² take the sq.root of C² that is the length from pumb cut at ridge to plumb cut on outside of wall plate allow for sheeting, or step it off with the framing square. The original Swanson Speed Sq. has marks for birds mouth. Working down from plumb line on the pitch is the correct way. Scribing rafters isn't required and seldom accurate. If you build square and level and know the span, pitch and how thick the ridge board is you don't need to do all the fiddling. Try that with a jack, valley jack, or hip and you can see the problem. 2x6's would also throw you a curve. The scribe method will also open up the top or toe creating a bad joint at the ridge board. Better go back and rethink this one. Learn the correct way and it is faster more accurate and make a good carpenter. I trained many since the late 60's. Commercial, Industrial and Res. All field of Carpentry and the other trades. You mean well. So don't think I am putting you down. Son we all gotta learn. I learned from the very best. Hope this helps you out. I can teach you step stringers or jacks and tricks for trim as well. Which direction you run crown and base. How to cope and scribe anything from a concrete form to paneling plywood and trim to fit like it grew there. Tricks and knowing the proper techniques. How to figure an octagon side or 6' ruler tricks and how to figure taxes on a framing square. Thank you for posting. 1/2 the width of the building less 1/2 thickness of the ridge board is the run. The rise is however many inch in each foot example in inches 4-12. A hip roof ridge is subtract the width from the length of the building. That is the length of the ridge board on a hip roof. Hips and valleys are rise or pitch and 17. Example is a 4 12 is 4 and 17. on the square. Careful here allow for the half of the rafter on the plumb cut depth so the top of the valley or hip match tge common rafters. Good luck.

[strongholds]

He didn't show you the top cut at the end because its not sitting down FLUSH.
Wrong angle, this is hack work.

[melmaddawgduran]

Failed to state, you need to raise the top same height to get that birds mouth to fit correctly. Good idea though.

[KaliBlaz]

thank you, everyone on YouTube tries to make this a math competition.

[nealbarker]

Don't forget if marking in situ you need to make sure your rafter is raised above the ridge by the amount you plan to cut out on the birdsmouth, normally you work in 3rds so 1 3rd of timber above ridgeline, the 3rd up from the wall plate

[kellyfreeman]

For some. Close enough is good enough. This makes me thankful for my mentors.

[Louis-opzj]

Works practically, but technically it would be out of square with your top plate by an umteenth of a degree as the rafter will drop for the birdsmouth. To do it so it is closer to square would be to pin the rafter to the ridge, sitting higher by the approximate depth of the birdsmouth (generally no more than a 3rd the width of your timber or you lose strength for the overhang) then mark and it should be closer but again may not be perfect, in saying that, the math isn't impossible and once you get your head around it it's much easier than it sounds. They also have applications and websites that figure this all out for you.

[blainecelestaine]

I appreciate you showing this. A person must know the measurements. This will help you mark the mouth but the ridge and tail will often have the same pitch cut. And the measurement is from the outside of the wall to the top and bottom of the ridge. The difference between those length marked on one end of a rafter will give you pitch. Then pull your tape from either the bottom mark or the top along the rafter to the spot where your square laid horizontal place the top of the birds mouth cut. Transfer the pitch there and at the tail of the rafter.. Now if there all the same that's your pattern without having to know how to read a framing square. My.02

[mikeznel]

Well thats one way to do it but by the time you cut the top angle at the ridge and the rafter drops because of the birds mouth, its not gonna be a tight joint.

[TheDaddytoybox]

No simpler explanation can be given. I see lots of comments about fit and measurement. String line from ridge to plate with a scrap cut of wood can insure your fit. Great no frills explanation!