600
Section 4 Finishing
Winding stairs, also called geometrical, are
circular or elliptical. They gradually change
directions as they ascend from one level to
another. These often require curved wall
surfaces that are diffi cult to build. Because of
their expense, winding stairs are usually only
found in high-end homes.
18.2 Stair Parts
Stairs are basically sets of risers and treads
supported by stringers, Figure 18-5. The rela-
tionship between the riser height (unit rise)
and the tread width (unit run) determines how
easily the stairs may be negotiated. Research has
indicated that the ideal riser height is 7″, while
the ideal tread width is 11″.
Headroom is measured from a line along
the front edges of the treads to the enclosed
surface or header above. This distance is usually
specifi ed in local building codes. Refer to
Figure 18-5. The Federal Housing Adminis-
tration (FHA) requires a minimum headroom
of 6′-8″ for main stairs and 6′-4″ for basement
or service stairs. Local codes may have other
requirements.
18.3 Stairwell Framing
Methods of stair building differ from one
locality to another. One carpenter may cut and
install a carriage (stringer) during the wall and
fl oor framing. Another may put off all stairwork
until the interior fi nishing stages. Figure 18-6
shows several stages of stair building.
Regardless of procedures followed, the rough
openings for the stairwell must be carefully laid
out and constructed. If the architectural draw-
ings do not include dimensions and details of
the stair installation, then the carpenter must
calculate the sizes. Follow recognized standards
and local code requirements.
Winding stairs: A curving stairway that gradually
changes direction; usually circular or elliptical in
shape. Also called geometrical.
Riser: The vertical stair member between two consec-
utive stair treads.
Tread: Horizontal walking surface of a stair.
Unit rise: The height of the stair riser; the vertical
distance between two treads.
Unit run: The width of a stair tread minus the
nosing.
Headroom: The clear space between the fl oor line and
ceiling.
Tread
Riser
Unit run
Unit rise
Headroom
Stairwell
R.O.
Finish
floor
Total
rise
Stringer
(or carriage)
Preferred angle
30 35
Total run
Figure 18-5. Basic stair parts and terms. The total
number of risers is always one greater than the total
number of treads.
Third
level
Platforms
Second
level
Flights
First
level
Basement
level
Figure 18-4. Stair runs are often made one above the
other to gain headroom. This one is designed for a
split-level home.