Stair Planning

We’ve got two parallel tracks for the next little while: framing the first floor and the mechanical room plumbing. For now I’m working on the framing. My friend Matt B. will be down tomorrow and Friday to help work on the house, so we’ll be tackling the opening for the stairs in the first floor. In order to be ready I had to go back over the stair calculations, re-measure everything and come up with the final plan and position of the stairs. The stairs are extremely complicated because everything has ripple effects and there are some tight constraints.

Stair planning

For example, the first floor stairs will go straight up to a landing, turn right 90° and go up the remainder. The bottom of that landing needs to be more than 80″ above the floor so that we can put the stairs down to the basement underneath it. The stairs from the second floor to the attic are above the first floor stairs. Those stairs have a landing directly above the first floor stair landing. We need at least 80″ from the top of the first floor landing to the bottom of the second floor landing plus another 80″ from the top of that landing up to the roofline, and there needs to be a consistent rise and run to the stairs to allow them to get to the correct height at the correct place.

To further complicate things, the brick foundation is thicker than the frame walls, so the finished first floor wall will be 9″ from the finished basement wall. In order to have the minimum 36″ stair width going down to the basement, the stairs above them must be wider, which means the landing must be wider and deeper, and the stairs from the landing to the second floor have that much less space to go up the remaining distance because they can’t go through the LVL beam we just put in. Despite all of that, we did have some play in where the stairs could go front-to-back. Moving them back makes the front bedroom on the second floor bigger, but the coat closet, pantry, and walk-in closet in the master suite smaller. We eventually figured it out.

First floor stair opening

Despite the stick drawing of the stairs, I did account for the head room under the stairs after stringers and drywall. Everything checks out, but it’s very close to the 6′ 8″ minimum height. I’d really like to have more clearance, not just for tall people but for moving furniture, but unfortunately there’s no good way to fit more in without building a dormer in the attic above the stairwell, something we really don’t want to do.

The stairs from the first floor to the second will be 42″ wide with 11″ treads (including a 1″ bullnose). From the floor to the landing they’ll rise 7 ⅝” per step, and from the landing to the second floor they’ll rise 8″. The stairs to the attic and basement will have an 8″ rise and a 10″ tread. We’ll build the stairs from framing lumber (rimboard for the stringers, OSB for the risers and treads), and eventually cover them with finishing treads and risers that match our floors.