This is a great question, and I wish I could help you with this
project. It sounds fun. Okay, you need to first figure out how many
stairs you will have.

Determine number of stairs: Take total height and divide by 7" (this
is the ideal stair height). You will most likely not get an integer
number. So, round it either way. Let's call this number N. Now
divide your total height by N. This is how tall each of your risers
will be. The total number of stairs you will need will actually be
N-1, because the floor at the top of the stairs will serve as the last
stair.

Determine the angle: 30 degrees sounds about right, but I don't know
this one for sure. But I would say that once you begin, it will be
tricky to make sure your last stair ends up in the right location
relative to the second floor. I might be inclined to start my layout
from the top stair.

The curved rail is the biggest challenge here. I once built an
elliptical-shaped wall cap, and I did it using a large (very large)
scribe. I actually used an existing curved wall, and then drew the
pattern on the side of the wall, and then built the wall cap against
the wall. This information is probably useless to you. But I would
probably build a cylinder of the appropriate diameter. You can do this
with plywood plates and studs. Then I would use this as my model and
go from there. Hopefully someone else will have a better answer than
mine.

Good luck, and have fun.



Chris wrote:
I would like to do myself a wood spiral staircase for my country house
(not expensive).
The diameter should be 4' and the high is 8'
How many treads should I take into consideration? What should be the
angle between threads? (Is 30 deg. correct?)
How should I do the curved rail?
Or could you suggest me some technical specification.

Thanks,
Chris