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Section 4 Finishing
18.7 Stringer Layout
To lay out the stair stringer, fi rst determine the
riser height. Place a story pole in a plumb position
from the fi nished fl oor below through the rough
stair opening above. On the pole, mark the height
of the top of the fi nished fl oor above.
Set a pair of dividers to the calculated riser
height and step off the distances on the story
pole. There will likely be a slight error in the
fi rst layout, so adjust the setting and try again.
Continue adjusting the dividers and stepping
off the distance on the story pole until the last
space is equal to all of the others. Measure the
setting of the dividers. This length is the exact
riser height to use in laying out the stringers.
To create a cut-out stringer for a simple base-
ment stair, select a straight piece of 2 × 10 or 2 × 12
stock of suffi cient length. Place it on sawhorses
to make the layout. Begin at the end that will
be the top and hold the framing square in the
position shown in Figure 18-14. Let the blade
represent the treads and the tongue represent
the risers. For example, if the risers are 7 3/4″,
align that mark on the tongue with the edge of
the stringer. If the treads are 10″, align that mark
on the blade with the edge of the stringer.
Draw a line along the outside edge of the
blade and tongue. Now move the square to
the next position and repeat. The procedure
is similar to that described for rafter layout
in Chapter 10. Continue stepping off with the
square until the required number of risers and
treads have been drawn, Figure 18-15.
The stair begins with a riser at the bottom,
so extend the last tread line to the back edge of
the stringer. At the top, extend the last tread and
riser line to the back edge.
One other adjustment must be made before
the stringer is cut. Earlier calculations that gave
the height of the riser did not take into account
the thickness of the tread. Therefore the total
rise of the stringer must be shortened by one
tread thickness. Otherwise the top tread will
be too high. The bottom of the stringer must be
trimmed, as shown in Figure 18-16.
Working Knowledge
Extreme accuracy is required in laying out
the stringer. Be sure to use a sharp pencil or
knife and make the lines meet on the edge of the
stock. Accuracy can be assured in this layout
by using framing square clips or by clamping a
strip of wood to the blade and tongue.
Rise
Run
Minimum 4"
Framing
square
Figure 18-14. Using a framing square to lay out a
stringer.
Figure 18-15. A completed stringer layout will look something like this.
Tread
thickness
Cut on this line
Figure 18-16. Trim the bottom end of the stringer to
adjust the riser height for the tread thickness.