Installation Guide
12
Remembering that your objective is to space balusters
evenly throughout the balustrade, find the locations of the
second and/or third balusters on the tread using the
following formula:
Example: (Using the figures from Fig. 8-6)
If you are placing three balusters per
tread and the run is 10
1
/2", the distance
between centerpoints will be
NOTE: All baluster and newel centerpoints will be located
at this interval on the baluster line, throughout the entire
balustrade. (Even though newel diameters are larger, the
newel centerpoint should be located exactly where the
baluster centerpoint would be.) Placement on each tread is
measured from the first baluster centerpoint, as
determined above.
WARNIN
G
:
Building codes are increasingly requiring
adherence to something called the “Four-Inch Sphere
Rule.” Currently, the IRC 2003 code in most states
requires baluster spacing on open treads that does not
permit pass-through of a 4
3
/8" sphere. Baluster profile and
spacing are the two variables which determine your
compliance. You may be required to use three balusters
per tread to comply with this rule. As always, be aware of
local building codes. Refer to Appendix 5 (page 58) for
more information.
Now, mark the centerpoints of all the balusters on the
baluster line.
Riser
R
un
Tread
Baluster
centerpoint
Baluster
s
quare
F
ormula sample:
Distance from riser to
centerpoint of first baluster
10
1
/
2
" -
1
3
/
4
"
2
=
9
5
/
8
"
(
10
1
/
2
"
)
(9
5
/
8
")
S TEP
B.1a
SECTION B
1
1
Now find the location of the first baluster on the tread. It
will be on the baluster line, and the leading face of the
baluster should be in line with the face of the riser beneath
the tread (see Fig. 8-4).
The mathematical formula is:
WARNING: If the first baluster is not correctly positioned, it
may not be long enough to properly penetrate the rail.
Half newel
Adjusted
baluster
centerline
True
baluster
centerline
SECTION B
FIG. 8-5 - First baluster position: mathematical method
S TEP
B.1a
FIG. 8-3 - Adjusting baluster centerline for termination into a wall
Outside
face of
baluster
Tread side edge
Side view
Leading face
of baluster
Cove molding
Finished wall/
skirt board
Face of
riser
Baluster thickness
Tread overhang
Baluster centerline
FIG. 8-4 - Adjusting baluster centerline for termination into a wall
run
no. of balusters
=
distance between centerpoints of
balusters (and newels) throughout
the overall run (see Fig. 8-6)
run –
baluster square
thickness
distance from front
edge of tread to
center of first baluster
(see Fig. 8-5)
=
10" – is the same as 10" –
7
/
8
" = 9
1
/
8
"
1
3
/
4
"
2
10
1
/
2
"
3
= 3
1
/
2
"
2
tread
overhang
+
distance from top
of starting tread to bottom
of starting fitting
rake
rail
height
vertical
thickness
of rail
+
–
block
height
balcony
rail
height
balcony
rail
thickness
rake
rail
height
rake rail
thickness measured
on the plumb
=
–––
(
)
run
no. of balusters
=
distance between centerpoints of
balusters (and newels) throughout
the overall run (see Fig. 8-6)
run –
baluster square
thickness
distance from front
edge of tread to
center of first baluster
(see Fig. 8-5)
=
10" – is the same as 10" –
7
/
8
" = 9
1
/
8
"
1
3
/
4
"
2
10
1
/
2
"
3
= 3
1
/
2
"
2
tread
overhang
+
distance from top
of starting tread to bottom
of starting fitting
rake
rail
height
vertical
thickness
of rail
+
–
block
height
balcony
rail
height
balcony
rail
thickness
rake
rail
height
rake rail
thickness measured
on the plumb
=
–––
(
)
run
no. of balusters
=
distance between centerpoints of
balusters (and newels) throughout
the overall run (see Fig. 8-6)
run –
baluster square
thickness
distance from front
edge of tread to
center of first baluster
(see Fig. 8-5)
=
10" – is the same as 10" –
7
/
8
" = 9
1
/
8
"
1
3
/
4
"
2
10
1
/
2
"
3
= 3
1
/
2
"
2
tread
overhang
+
distance from top
of starting tread to bottom
of starting fitting
rake
rail
height
vertical
thickness
of rail
+
–
block
height
balcony
rail
height
balcony
rail
thickness
rake
rail
height
rake rail
thickness measured
on the plumb
=
–––
(
)
Tread
Baluster
centerpoints
Baluster
squares
3 balusters
per tread
Riser
Run
(10
1
/
2
")
Formula sample:
=
10
1
/
2
"
3
3
1
/
2
"
Distance is equal between
centerpoints of all balusters
and newels throughout the
overall run.
For placement on each tread,
measure from centerpoint of
the first baluster on each tread.
3
1
/
2
" 3
1
/
2
"3
1
/
2
"
FIG. 8-6 - Second/third baluster position: mathematical method