How can I place treads on these stairs around a corner?

Question

I have built the start of these stairs. It's a difficult concept for me to build stairs around a corner so I cut part of the deck so it wasn't an abrupt 90 degrees going into the stairs (which wouldn't have really worked anyways).

I am at the point now of putting the tread on the stairs. I have a few boards screwed down already to keep the spacing between the stringers the same but how do I go about getting rid of the gap between the first tread and the stringer "toes" edge?

You can see in my picture there is a gap where I placed my pencil. My plan was to cut the boards at the same angle the stringers are at. So basically every board will end on a full 2x4 stringer top. Thats why I doubled some stringers. Any thoughts? Even if I cut the board on the left at an angle I will still have that gap. You should be able to see the pencil in both pictures.

Answer 1

So you have two issues: the cut angle and the gap.

Cut Angle

Whenever two boards meet at and angle, you have to cut each board by half of the angle in order to get the edges to line up. So, in the top-down picture with the pencil, lets say that is a 30 degree angle. Cut each board at 15 degrees. You can't cut the board to line up with the stringer - you have to "split the angle".

Mind the Gap

Again, using the top-down picture, the board on the right will be in the "correct" position because its naturally perpendicular to the stringers. The left board hits the stringer at a 30 degree angle, so either you will have to cut a small, triangular notch out of the board, or make a notch in the stringer for the board to fit into. Notching the board (probably with a jigsaw) will be the easiest option, and when you're done, the fronts of the two boards should line up. To make getting the notch in the right place easier, cut the notches with extra board hanging out over the edge before trying to cut the 15 degree miter to meet the other board.

I may be able to add a drawing later if this isn't clear enough, but I think it should get you going in the right direction.

*Obviously I made up the 30 degrees measurement. Get an angle guide to measure each one before cutting.

Answer 2

If you want the steps to follow the edge of the deck you need to add more stringers. The double stringers you have can remain but you need doubled stringers at locations that bisect (cut in half) the angles the stairs make as they go around the deck. Here is a rough sketch to give the idea.

The run of the stair will change to compensate for the angle these stringers run.