Follow my honest first attempt at cutting a birdsmouth joint for a shed roof. See where I went wrong, learn key woodworking lessons, and discover what not to do before Round 2!
It might help to think about the project as a journeyman would. What’s the pitch of your roof? 3/12, 4/12,5/12???etc. Find your pitch by using a framing square, and that gives you both angles. If your sloped wall is raked at an angle of, say, 4/12, then the heights of the bottom and top wall can be adjusted to produce a birds mouth cut on each. Usually on a job, we start by knowing height of the low wall and the pitch. Your choice of running 2x4 rafters flat is unusual and more difficult.
This was a bit of a late revelation for me. I set myself down the wrong path from the start, and rather than take a step back, I just got myself in a mess. Next time will be much better!
This might not answer your question because I’ve never seen a german square. The slope or pitch of any roof is visible is on building plans on the elevation page and is called out as the result of two factors: the rise and run. On imperial scale American roofs those numbers are in inches. For most gable roofs the run is a given, always 12 inches which you would find on one blade of a framing square. Slope or pitch is expressed as 1”/12” or 5”/12” or 12”/12” which is a 45 degree angle. Set the two perpendicular outside edges of the square down on a straight line. The long blade set at 12”. That’s the run. Now, say your pitch is 5/12. Ok, set the shorter blade of the square at 5”. That’s the rise. For every 12” inches of run the slope of the roof rises 5”. You can do the same in centimeters and get the same angle. If you mark the angles on a board, you can find the slope of the roof, the plumb cut at the ridge line and the seat cut which is the flat part of a birds mouth.
I looked at a German square online and though it has holes every five mm, it also has a scale inscribed on both blades, same as an American square. Setting run and rise will give you the slope.
Some of them do, the one I posted above does not. And when I have seen German Carpenters online doing timber framing their squares were like the Vogel square I posted above.
I’m trying to figure out how to show you what one looks like. I don’t understand why I can’t paste a photo. Here is a link to a German carpenter square (I don’t mean a try square but what is a framing square for them). There is no scale. Maybe it counts on you knowing the lengths of the legs.
I’m interested in figuring out how German carpenters use their squares to do this since their large carpenter squares aren’t marked like a Stanley or Starrett rafter table framing square. It does have some marking holes on the short leg, but it doesn’t have any of the rulers or data tables that the framing squares I normally see have.
It might help to think about the project as a journeyman would. What’s the pitch of your roof? 3/12, 4/12,5/12???etc. Find your pitch by using a framing square, and that gives you both angles. If your sloped wall is raked at an angle of, say, 4/12, then the heights of the bottom and top wall can be adjusted to produce a birds mouth cut on each. Usually on a job, we start by knowing height of the low wall and the pitch. Your choice of running 2x4 rafters flat is unusual and more difficult.
This was a bit of a late revelation for me. I set myself down the wrong path from the start, and rather than take a step back, I just got myself in a mess. Next time will be much better!
Thanks for the comment!
This might not answer your question because I’ve never seen a german square. The slope or pitch of any roof is visible is on building plans on the elevation page and is called out as the result of two factors: the rise and run. On imperial scale American roofs those numbers are in inches. For most gable roofs the run is a given, always 12 inches which you would find on one blade of a framing square. Slope or pitch is expressed as 1”/12” or 5”/12” or 12”/12” which is a 45 degree angle. Set the two perpendicular outside edges of the square down on a straight line. The long blade set at 12”. That’s the run. Now, say your pitch is 5/12. Ok, set the shorter blade of the square at 5”. That’s the rise. For every 12” inches of run the slope of the roof rises 5”. You can do the same in centimeters and get the same angle. If you mark the angles on a board, you can find the slope of the roof, the plumb cut at the ridge line and the seat cut which is the flat part of a birds mouth.
German carpenter squares are not the same.
I looked at a German square online and though it has holes every five mm, it also has a scale inscribed on both blades, same as an American square. Setting run and rise will give you the slope.
Some of them do, the one I posted above does not. And when I have seen German Carpenters online doing timber framing their squares were like the Vogel square I posted above.
I’m trying to figure out how to show you what one looks like. I don’t understand why I can’t paste a photo. Here is a link to a German carpenter square (I don’t mean a try square but what is a framing square for them). There is no scale. Maybe it counts on you knowing the lengths of the legs.
https://shop.vogel-germany.de/squares/carpenter-square-with-marking-holes-600-mm-x-280-mm.html?language=en
I’m interested in figuring out how German carpenters use their squares to do this since their large carpenter squares aren’t marked like a Stanley or Starrett rafter table framing square. It does have some marking holes on the short leg, but it doesn’t have any of the rulers or data tables that the framing squares I normally see have.
Honest post! Looking forward to round two.
Thanks! :)