On The Job Mathematics
For Wall Framing
By Steven W. Anderson
AM or PM Class
Name:__________________________
School:____________ Grade:_____
Date Started:_________ Age:_____
Directions: Read each of the problems carefully and answer them in order. Refer to the pictures and
Reference Guide as needed for extra help working out the problems. Do your own work and don't distract other
students from their work by asking them questions. For additional help ask your teacher. Write down all
scratch-work close to the problem you are working on, save it, do not erase, as this will help if you need to
make corrections later. All work will need to be 100% correct before you will receive credit for this math unit.
After the floor framing is complete next comes the wall framing. First you need to locate the walls by snapping
chalk lines on the sub-floor. Using the partial floor plan below, fill in dimensions A, B, C, and D.
Note: Interior walls are 4 1/2" thick.
A. =_____' - ______"
B. =______' - ______"
C. =______' - ______"
D. =______' - ______"
2
To set a wall straight, you first need to snap a chalk
line on the subfloor alone the entire edge of the wall.
What is dimension F in drawing at right? This is the
distance from the outer edge of the floor framing to
the inside edge of the exterior walls.
Note: 2"x4" are actually 3 1/2" wide.
F =_______"
2"x4"
Stud
1/2"
Plywood
1" Foam
F
.
2"x10"Joist
What is the total length of the house (dimension G) in the partial drawing below?
Note: Interior walls are 4 1/2" thick.
G =_____' - ______"
8" Concrete
3
Fill in the missing dimensions from the partial drawing below. Note: Interior walls are 4 1/2" thick.
H =_____' - _____"
I =_____- ______"
J =_____' - _____"
K =_____' - ______"
4
After the chalk lines locating the walls are marked on the subfloor, the next step is to layout the wall plates.
How many L.F. of wall plate material do you need for the walls in red below (add 10% for waste)? Remember
the walls are made up of a bottom and two top plates. Don't reduce the amount for openings or wall finish
materials. Note: Interior walls are 4 ½" thick; exterior walls are 6" thick; round answers up to the next full L.F.
L.F. of wall plate = __________
Amout for waste = _________
Total L.F. of wall Plate = __________
How many 16' long boards will you need to buy for the wall plates in the previous problem? Note: Round up
your answer to the next full-length board.
Number of 16' boards ____________
5
If the stud walls in the drawing below are laid out 16" O.C., how many studs will you need to buy to construct
the walls in red (use the L.F. of walls determined in the previous problem)? Note: To determine the number of
16" O.C. studs, simply multiply the total L.F. of walls times 3/4, and then add two extra studs for every corner,
intersection, and opening.
Number of studs 16" O.C. = ___________
A.
B.
C.
D.
E.
WINDOW AND
DOOR SCHEDULE
R.O.
38"
WIDTH
R.O.
25"
WIDTH
R.O.
49"
WIDTH
R.O.
42"
WIDTH
R.O
75"
WIDTH
A.
A.
C
C
B
E
A
A.
D
D
6
The house plan specifies double 2"x12" headers (as shown on
the right) for all exterior window and door openings.
Approximately how many L.F. of 2"x12" material will you need
to buy for the exterior window and door openings in the
drawing on Page 5 (add 10% for waste)? Round your answer
up to the next full L.F. Note: Use R.O. width for header
lengths.
Plywood
Spacer
Wall
Header
3 ½”
L.F. of 2"x12" = ________
If the lumber company only has 2"x12"x8' in stock, how many boards will you need to buy for the headers in
the previous problem? Note: Round up answer to the next full-length board.
Number of 2"x12"x8' boards for headers = ___________
If the overall header needs to be 3 ½" thick and the header boards are 1 ½" thick, what plywood thickness do
you need for the spacer? What would the spacer thickness be for a 5 ½" thick header?
Spacer Thickness for 3 ½" Header = ________"
Spacer Thickness for 5 ½" Header = ________"
If the house plan also specifies double 2"x4" headers for all interior walls, how many L.F. of 2"x4" material will
you need to buy for the interior walls marked red in the drawing on Page 5 (add 10% for waste)? Round your
answers up to next full L.F. Note: These interior headers will look like the exterior headers, but are built from
2"x4" instead of 2"x12" boards. Use R.O. width for header lengths.
L.F. of 2"x4"
= _________
Amount for waste = ________
Total L.F. 2"x4" = _________
7
If the stud walls in the drawing below are laid out 24" O.C., how many studs will you need to buy to construct
the walls in red? (use the L.F. of walls determined in problem at the top of Page 4)
Note: To determine the number of studs multiply the total L.F. of the walls times ½, then add two extra studs
for every corner, intersection, and opening.
Number of studs 24" O.C. = ___________
If the R.O. height of the door in the picture is 6'-10", what size will you need to cut the door trimmers?
Note: The sole plate is 1 ½" thick.
Trimmer length = ______' - ______"
What if the R.O. is 84"?
Trimmer length = ______' - _______"
R.O.
6’ –10”
Trimmer
8
In the drawing at the right, the window
header height is 6'-10" as in the previous
problem. What are the sizes of boards A.
and B. to make up the split window
trimmer? Use the R.O. sizes below?
Note: Windowsill and wall plates are 1 ½"
thick.
R.O. = 2'-7 5/8"
A.
R.O.
A. = _______' - ________"
B. = _______' - ________"
R.O. = 3' -5 5/16"
A. = _______' - _______"
B. = _______' - _______"
R.O. = 5'-9 1/8"
A. = _______' - _______"
B. = _______' - _______"
If the B.R. windows (below) are centered using interior dimensions, what are dimensions A. and B?
A. = _______' - _______"
B. = _______' - _______"
B.
9
Using the drawing on the right, determine the cripple stud lengths above the window needed for each of the
header sizes below. Note: The full-length studs are 92 5/8" long.
2x4 Header (3 ½”) size = ______" cripple length
Cripple
Studs
Header Size
2x6 Header (5 ½”) size = ______" cripple length
6’ –10”
2x8 Header (7 ¼”) size = _______" cripple length
2x10 Header (9 ¼”) size = ______" cripple length
10
When you look at house plans, the walls and wall intersections
often are dimensioned to their center. At intersections, a
partition post (or P-Post) is usually placed (see drawing on the
right). Look at the P-Post widths below and determine the
distance from P-Post center to its outer edge?
P-Post width 6 1/2"
Distance from center to edge = ________"
P-Post width 8 1/2"
Distance from center to edge = ________"
When laying out wall plates you can't just mark the stud
centers. If you did, the stud would cover up the mark and
you couldn't be sure of the correct location. You need to
mark lines for the edges of studs. These lines are drawn off
center ½ the stud thickness. If the studs in the house you
are building are 1 ½" thick, what is the ? dimension? This
is how far from the stud center to mark for the stud edge?
? =__________" back from center of joist
P-Post
outer
edge
P-Post
Width
11
When nailing a 1 ½" thick top plate
to the studs, how far will the 3 ¼"
nail penetrate into the stud?
________"
When nailing trimmers to studs in window and door
openings, the end of the nail will protrude through the
backside. This nail can be dangerous if you were to
snag on it while working. Nailing at an angle will stop
the nail from coming out on the backside. How far
would the nail in the drawing protrude out the back if it
were hammered straight through?
Nail will protrude out back ________"
12
Determine dimension A. in the drawing below if the R.O. is 75 3/8". Dimension A. is the distance from the
center of the sliding door to the inner edge of its trimmers. If the header length is 3" longer than the R.O., what
is the header length for this slider door?
A. = _______' - ________"
Header length = _______' - ________"
Determine dimension A. and header length in the drawing below if the R.O. is 73 5/8".
A. = ______' - ________"
Header length = _______' - ________"
Determine dimension A. and header length in the drawing below if the R.O. is 62 ¾".
A. = _______' - ________"
Header length = _______' - ________"
R.O.
13
What is the total height of the wall with these members?
Sole plate
Stud
Top plate
Double Top Plate
1 ½"
92 5/8"
1 ½"
1 ½"
Total height = _______' - ________"
Sole plate
Stud
Top plate
Double Top Plate
1 ½"
8'
1 ½"
1 ½"
Total height = _______' - ________"
Sole plate
Stud
Top plate
Double Top Plate
1 ½"
9' 7 1/2"
1 ½"
1 ½"
Total height = ______' - ________"
Many times backing is placed in walls to mount curtain
brackets, towel racks, plumbing, etc. What is the length of the
backing board for a 16" O.C. wall (dimension A.) in drawing
at the left?
Length A. = ________"
What is A., the backing board length for a 24" O.C.
wall? (Drawing at the right)
Length A. @ 24" O.C. = ________"
14
Headers for windows and doors are normally 3" longer than the rough opening (R.O.).
What is the length of the door header if the R.O. is?
Header
25 ¼" R.O. = door header _____' -_______"
26" R.O.
= door header _____' -_______"
32" R.O.
= door header _____'- ______"
34" R.O.
= door header _____' - ______"
36" R.O.
= door header _____' - ______"
38" R.O.
= door header _____' _______"
R.O.
50 ¼" R.O. = door header _____' - ______"
What is the header length needed for windows with R.O.
shown below? Note: trimmers are 1 ½" thick.
Header
R.O. = 2'-7 5/8"
Header Length = _______' - _______"
R.O.
R.O. = 3' -5 5/16"
Header Length = _______' - _______"
R.O. = 5'-9 1/8"
Header Length = _______' - _______"