Stair Stringers
Stair stringers are the main supports for the stairway.
When choosing your 2 x 12 or 2 x 14 stringers make sure you pick the
straightest lumber available. Don't accept any pieces that have knots or
obvious weak spots in them. You can visually look at a piece of lumber
and see the big knots or cracks that will create a safety hazard and
possible stringer damage later on.
Stair Stringers
If you find a nice Straight piece of wood and it does have large knots throughout the board and you think you can lay out the stair stringer around the knots then go ahead and use the board for your stair stringer.Pick out the best piece of wood for your first stair stringer. This will allow you to lay out your stair stringer effortlessly. Doing this you will avoid most cracks or knots in the wood when laying out your first stair stringer.
After you have cut your first stair stringer you will be able to lay it on top of the next 2 x 12 or 2 x 14 and then trace the next stair stringer using the first stair stringer as a pattern.
You can slide the stair stringer pattern in either direction to avoid a large knots and even cut some of them out completely.
You can use the first stair stringer as a pattern to cut out as many stair stringer's that are required for your stair project.
There are different grades of lumber to use when building a house. For stair stringers it will be a good idea to use number one or select grade materials. If you are hand selecting your stair stringer materials from a local lumberyard or home improvement center you can use number two grade lumber. If you use number two grade lumber for your stair stringers, be careful to select a piece that is nice and Straight with small tight knots.