7:00
material for ceiling joists is very similar to floor joists. Calculate number of joists on each side of the
center load-bearing wall. We will calculate the number of each even length joists needed.
FORMULA for # of CEILING JOISTS (per span)
# of Joist LF perpendicular to joist x space factor + 1 (starter)
Ceiling Beams and Bracing
Beams are placed in the ceiling joists to eliminate drops in the ceiling at doorways. The beams
may be similar to methods and materials used for girders. A built-up beam needs to bear at least 2" on
each wall. Joist hangers are needed for each joist on each side of the beam. A box beam is placed
above the ceiling joists with plywood saddles holding the joists up.
FORMULA for amount of BEAM MATERIAL
Material for Beam - Calculated per LF of Beam -
Strong backs and Stiffbacks
Two types of bracing are used for ceiling joists. A strongback or stiffback provide more support
to the joist than a rib band. A strongback helps keep the joists straight, especially when the plan has
large rooms. They are placed at mid-span and are secured to the end walls. For residential construction
a 2x4 is laid flat on top and nailed into each of the ceiling joist. A 2x6 is placed on edge and nailed into
the edge of the 2x4. Each type of material and each span need to be calculated for the house.
FORMULA for MATERIALS for STRONGBACKS
(per span)
Strongback Material = LF of Building (perpendicular to joists)
Rib band
The other ceiling joist bracing is a 1x4 nailed to the top edge of the joist. This keeps the joists
spaced "oc" and from twisting and bowing. The rib band is also placed at mid-span and secured to the
end walls. The rib band may also be called a "rat run". We calculate the even LF of material needed.
FORMULA for RIB BAND MATERIAL (per span)
Material for Rib band
=
L of Building (perpendicular to joists)
Drywall Backing or Nailers
A nailer is placed on top of walls when the joist is not next to the wall edge. This provides a
nailing surface for edges of ceiling material. On top of 2x4 walls a 2x6 is commonly centered, leaving
one (1") inch exposed on each side to nail or screw into. Depending on how the joists lay in relation to
the walls provides a variety of situations that may develop for the backing. We will estimate an amount
of 2x6 equal to two-thirds (2/3) the length of the interior 2x4 walls that run parallel to the ceiling joist.
The remaining one-third (1/3) will come from scrap material. We will estimate the even LF of 2x6
needed.
FORMULA for DRYWALL BACKING MATERIAL
Material for Backing = LF of walls parallel to joist x .6666
5-8
(2x6)
==‒‒‒‒‒‒‒[[[///// Wall Sheathing
Veneered panels, solid lumber, or non-wood products are common materials used for sheathing.
Rated sheathing or OSB are structural sheathings that provide stiffness to the wall and are used under
vinyl or steel sidings and brick veneers. The non-wood products (Black Jack, fiberboard, and rigid
insulating board) usually provide more insulating value. The veneered panels are 4x8, while the non-
wood products come in 4x8 or 4x9 sheets. Except for large openings, the sheathing is installed over
doors and windows then cut out later. Evaluate deductions for large openings. Divide the SF by 32 for
4x8 sheets and by 36 for 4x9 sheets. Estimate the number of sheets for the gable ends and add them to
what is needed for the walls. If different material is used as corner bracing be sure to make the
deduction. We will calculate the number of each type and size of sheathing needed.
FORMULA for # of SHEETS for GABLE END (# for one gable end)
# of Sheets SF of gable end divided by SF per sheet
FORMULA for # of SHEETS of WALL SHEATHING
# of Sheets
=
=
(4x9 sheets)
OSP divided by 4 + (# for gable end area) - (deductions)
B
OR
FORMULA for # of SHEETS of WALL SHEATHING (4x8 sheets)
# of Sheets = OSP divided by 4 x 1.125 + (# for gable end area) - (deductions)
7.00
Moisture and Air Barrier
Moisture barrier is placed directly under the siding to prevent water from penetrating into the
sheathing. An air barrier is a membrane that limits infiltration of air through the wall. Either a moisture
or a vapor barrier may also seal the wall against air infiltration. A vapor barrier is a membrane on the
warm side of the wall that retards passage of water vapor from the warm inside air into the cooler wall
where it could condense. This vapor barrier may be part of the insulation or a separate poly sheet.
Coordinating the components is critical to avoid trapping water vapor in the wall cavity. Products, such
as Tyvek serve as both a moisture and air barrier. Tyvek comes in rolls of 9'x195' or 1755 SF. The
joints of the material need to be taped to help seal out the air and moisture. When estimating be sure to
include the gable end areas. We will calculate the number of rolls needed.
of cons
br
FORMULA for NUMBER of ROLLS of AIR BARRIER
# of Rolls of Air Barrier = Exterior wall area divided by SF per Roll
CEILING FRAMING
Ceiling Joists
Ceiling joists tie the outside walls together, support the attic area, the weight of the ceiling finish
materials, and the tops of the interior walls. Generally the joists run parallel to the rafters. The span
and the weight that the ceiling must support determine the size of the joists. Stub joists are necessary
when a hip or low sloped gable roof is used on the house. If stub joists are used no additional material
is required compared to regular joists. A 2x6 placed 16"oc is typical construction for ceiling joists. To
produce smooth straight ceilings, 5/8" drywall should be used if the joists are 24"oc. To estimate for 8'1" high walls, cripple studs above the header are eliminated. For 2x4 stud walls, two 2x12's are
builders will use a 2x12 header on all exterior and interior load-bearing walls. By using a 2x12 header
nailed together with some ½" plywood strips sandwiched between to make the header 3 ½" thick. If
the subfloor is not " material, you may have to calculate some 2" ply for the spacers. Additional
material will need to be calculated for 2x6 walls. The maximum span for a solid stock 2x12 header is
about 10'. If greater spans are needed you may have to use an alternate material (LVL, Paralam, etc.).
We will estimate each opening separately. The actual length of the header is 3" longer than the
rough opening width (Hdr L = RO + 3") or 5 ½" longer than the doors width. (Hdr = 3'5 " for 30
door) Pocket door RO = 2 x door + 1". Keeping in mind that the dimensional lumber comes in even
lengths, use this formula for 2x4 walls. We will calculate the number needed for each size of even.
length header material. (4- 2x12x14, 6 - 2x4x8, etc.)
FORMULA for L of MATERIAL for HEADERS (2x4 stud walls)
L of Header Material
Opening width + 1'-0" (rd.off) x 2
Example:
2¹-8" door + 1'0" =
2'-6" door + 1'0" =
2-4" door + 1'0" =
3¹-8" (rd.up) to 4'-0" x 2 = 8'-0"
3'-6" (rd.up) to 4'-0" x 2 = 8'-0"
3'-4" (rd.down) to 3'-0"
x 2
= 6'-0"
10/01
We will use a 4x6 (2 - 2x6's) header for non-load bearing walls. An optional chart can be used
to determine the size of material for the headers. When truss rafters are used the load is carried to the
exterior walls, and the interior walls become non-load bearing.
Optional INTERIOR NON-LOAD BEARING WALL HEADER MATERIAL
Max.opening for 2x4 Hdr. = 3'-6", 2x6 = 4'-6", 2x8 = 6'-0", 2x10 = 8'-0", 2x12 = 10'-0"
Corner Bracing
We will discuss two types of corner bracing for the walls. Both provide lateral support for the
walls so they will not rack under heavy wind loads against the house. A rated sheathing or structural
panel can be placed at each exterior 270° corner, if a non-structural sheathing is used for the rest of the
wall sheathing. Two sheets would be placed at the corners, which are a min. wall length of 2'0". The
4x8 sheets will not cover the box header area, so a 1'x 4' piece of material will be calculated to cover
this area (1' of an 8' sheet = .125 sheet). We will calculate the number of 4x8 sheets needed.
FORMULA for # of SHEETS for CORNER BRACING
# of Sheets # of 270° corners x 2 x 1.125
A let-in brace is required at each end of the wall, if possible, and at 25' intervals. The let-in
brace should be placed from the top corner of the wall going towards the center at a 45° to 60° angle.
Typically the brace is a continuous 1x4. Use a twelve (12') foot 1x4 for an 8'1" high wall. We will
calculate the number of 1x4x12 needed for the 8' walls.
FORMULA for LF of LET-IN BRACE
LF of Let-In Brace = # of braces x LF per brace
5-6
IIII O
7:00
Contractors use one of several methods to estimate the quantity of studs, placed 16"oc. Several
will simply estimate one stud per LF of wall. We will use the formula that adds one stud per corner to
the LF of wall. Code stipulates that three (3) studs be placed in each corner. An estimator also needs
to evaluate a small area where several studs would be located to see if additional ones are needed.
(16" oc)
FORMULA for WALL STUDS
LF of Wall + 1 per Corner
# of Studs =
There are several optional formulas, which you might use, in special situations. The first one
most closely counts the number of studs. When the walls have an abnormal number of doors and
windows, such as a garage, you may want to use this formula.
OPTION 1 FORMULA for # of WALL STUDS
# of Studs = LF of Wall x space factor + 2 per corner, door, or window
OPTION 2 for STUDS 16" oc
# of Studs =
OPTION 3
LF of wall x 1.1
for STUDS 24" oc
# of Studs =
LF of Wall x .85
OPTION 4 for STUDS 12" oc
# of Studs
LF of Wall x 1.35
=
Gable End Studs
The gable end studs fill in the area between the top of the wall and the gable end rafter. The
wall sheathing and siding are fastened to them. The triangular shaped end will be converted to a
rectangle for finding the length and number of studs, for one end. To find the number of studs multiply
the span of the house, times the spacing factor. Because we are calculating a rectangular area divide
this number by 2, then round down. To find the length of a gable end stud, multiply the slope number
for the roof by the run, one half the span. The slope number for a 4-12 slope roof is "4". Convert the
length to feet and order to the most convenient even LF increment.
FORMULA for # of GABLE END STUDS (# for one gable end)
# of Studs = Span x spacing factor divided by 2
FORMULA for LENGTH of GABLE END STUDS
L of Studs (inches)
Slope x run (feet)
=
Door and Window Headers
All door or window openings in walls require some type of horizontal framing to support the
load being placed above the wall. If the framing member is located in the wall it is called a header. A
beam may be located in the ceiling joist to support this load. This will allow the ceiling height to remain
the same as it passes through the opening. We will examine the beams when we estimate ceiling joist
material. The header transfers the load of the ceiling and roof to the trimmers and then on down to the
foundation walls. A load-bearing wall will carry larger loads, so larger headers are required. Most
5-5
.
♦ BRIDGING
Bridging or blocking is installed between adjacent floor joist to provide lateral support. When
bridging is used it helps distribute the load and allows the floor to work as one unit. Some types of
bridging used are: prefab 1x3, 1x3 made from 1x6, solid, and metal. We will estimate the bridging
being placed @ 8' oc.
Cross Bridging
For the cross bridging one set will consist of two (2) pieces. Cross bridging will be placed
between joists spaced 16"oc (14 %2" space). For prefab sets calculate the number of 14 ½" spaces for
the floor system. The remainder of openings will have solid blocking. Openings that would not be
142" would be located at the first and last space; and where the extra floor joists have been installed.
When making the cross bridging from 1x6 material, 3.5 LF of 1x3 is needed for each set for 2x10,
16"oc joist. Divide the LF of 1x3 by 2 to convert to 1x6.
FORMULA for # of SETS of CROSS BRIDGING (per row)
# of sets = L perpendicular to joists x spacing factor # spaces containing solid bridging
FORMULA for LF of CROSS BRIDGING
LF of cross bridging = # of sets x 3'-6"
An optional method for calculating LF of material for cross bridging is to take the length of the
house times 2.5. The "2.5" is determined by multiplying the spacing factor times the length of one set
(.75 x 3.3334 = 2.5). This optional method allows for no deductions for solid bridging.
OPTION FORMULA for LF of CROSS BRIDGING
LF of Cross Bridging = L of House x 2.5
Solid Bridging
The same size material is used as the joists. When cross bridging is used then the solid blocks
are placed in those joist spaces that are smaller than 14 " If only solid is used, then the formula
places a block in each space. Order the material in a 4' increment if the LF of solid stock is longer than
18' and the joists are 16" oc. For 16"oc joist, we will use a 1'3" length for each block. The following
formulas are using 16"oc joist. We will calculate the even LF of material needed.
FORMULA for LF of SOLID BRIDGING (used with cross bridging)
LF Solid Bridging
# of spaces x 1'-3"
=
FORMULA for LF of SOLID BRIDGING
LF of Solid Bridging
=
per row
7.00
L of House x 75 x 1'-3"
5-3
(used w/o cross bridging)
.
.
•/n 4.0
PERNINCATATK
#1 lan
1. Girder (6x10) LF of 2x10
2. LF of sill sealer
3. LF of 2x8 PT mudsill
30.0
4. LF of 2x10 box header
5. No of 2x10x14' floor joist
6. No of 2x10x12' floor joist
7. No of 2x10x10' floor joist
M
10-10
30-0
Name
12-0
8. Number of sets of 1x3 bridging
9. LF of 2x10 solid bridging
10. No of sheets %" OSB subfloor
13. Total Cost
Floor Framing lan
11. No of quart tubes adhesive
12. No of sheets 3/8" plywood underlayment
1| Page
Estimating for Light Construction DDRT 1350 12-0
11'-0"
#2 Mariah
G
ELI
22-0
3'-0"
Estimate the plan and use the checklist to fill out a quantity take off form.
Girder-Built-up 6x8
Post-4 Lally columns
Sill Sealer-6"
Mudsill-2x8 PT
Bridging-1x3 prefab & 2x10 solid
Subfloor-glued %" OSB T&G
Underlayment - ½/2" plywood
10-10
26-0
Name
Floor Framing lan
2 | Page
Estimating for Light Construction DDRT 1350 #3 Savannah
2018, 1²0.C
FLOOR JOIST
17.P
23:10, 1678.C
FLOOR JOIST
10
PULL
4-4
189 SUBFLOOR
12-165
Name
Floor Framing lan
3 | Page
Estimating for Light Construction DDRT 1350
