CHAPTER D4 – Topic 1 – Frame Exterior Walls

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Section 3D – Constructs Wall Systems

Chapter D4 – Constructs Dimensional Lumber and Steel Stud Wall Framing

Topic 1 – Frame Exterior Walls

Types of Wall Framing

There are two systems used for wall framing: western (platform) framing, and balloon framing (see figure 1 and 2 below). While there are many parallels between each, they differ by their method of starting the frame at the foundation, the length of the studs, and method of floor framing at each level.

In platform framing, each wall is one storey high. The floor is framed as a separate system and the first storey walls are built on top. If a second storey is built, a second floor system is installed on top of the first storey walls. This system is used almost exclusively.

Balloon framing the wall studs are situated on top of the foundation sill plate. The studs run the entire height of the building. The second storey floor system is supported by the studs with a combination of a ribbon (or ledger) and face nails into the studs. The ribbon is inserted into notches which are cut into the studs.

Framing Openings in Exterior Walls

Openings in exterior walls all contain specific parts that are shown in the image below:

– Trimmers – these members transfer the load above the opening to the floor system below. The are face nailed to one or two full length studs (depending on the opening width) and are doubled in certain situations. The lintel (B) rests directly on them.

– Lintel – also known as a header, it is similar to a beam. It spans the opening width and carries the load above which is then transferred through to the trimmers.

– Cripple – situated at the stud centers, the rough sill is attached to the top of them. They do not carry loads from above.

– Studs – making up the frame of a wall, full length studs are also attached to the trimmers to extend to supporting members to the top plate. When attached to a trimmer, they are sometimes known as king studs.

– Rough Sills – act as a frame for an opening and a plate for the cripples. A top sill may be installed in desired but must not rest on the trimmer ends.

– Top Plate – The structural member which ties the wall together. All studs and top cripples are nailed to the top plate.

– Double Top Plate – Often added for wall height and to add rigidity to the top of a wall. Joints are staggered with the first top plate at least one stud space. Required where roof trusses or rafters are not situated directly above the stud centers.

– Bottom Plate – ties the bottom of the studs in place. In balloon framed walls, the sill plate acts as the bottom plate.

Door Opening are framed in much the same way, but do not have a rough sill or cripples underneath. The bottom plate is also removed inside the door opening after the wall is stood.

Finding Required Header

The size of header required can be found in Tables 9.23.12.3-A, B, and C. There are a number of factors which influence what size is required:

– Species – This is indicated in the title of each table; ensure you are using the correct one.

– Supported Load (see tributary width* below) – in left most column of each table, there are 6 different loads that are carried by the lintel. The type of building (1-4 storeys), the level the lintel is on, and which exterior wall it is placed will have an effect on this factor. Examples of scenarios to watch for:

The load supported refers to the structure above. If a lintel is placed on the second storey of a two storey house, it is only supporting the roof and ceiling. A lintel placed on the first storey of a two story house is supporting is supporting the roof, ceiling, and 1 storey
Only end walls with overhangs of 12” and a rafter spacing of 24” (or overhangs of 16” and 16” rafter spacing) use tributary width of 0.6 m
All lintels within side walls, and any end wall with an overhang of 24” has a tributary width greater than 0.6 m

– Snow Load – Given for exercises but may be found by location in Appendix C of the NBC vol. 1.

– Span – this is the clear space between the trimmers or the width of the rough opening. Tables 9.23.12.3-A, B, and C assume non-structural sheathing is applied. When structural sheathing is applied, the spans on these tables can be increased by 15%.

Example: a 2 ply 2×10 Douglas Fir lintel supporting a roof and ceiling in a side wall with non-structural sheathing under a 2.0 kPa snow load is able to span up to 2.03 m. If structural sheathing were to be applied, that same lintel is now able to span 2.33 m (2.03 + 15%).

* Tributary width is essentially the “supported length” for lintels. In side walls, this is equal to half of the span of the rafters. Only applying to gable end walls, it is the length of overhang plus half of the rafter spacing. In most cases, the tributary width of 0.6 m is exceeded, and we would use the maximum tributary width of 4.9 m instead. In hip roofs, the tributary width of 0.6 m is disregarded.

Example 1: Find the lintel required

Bungalow House, lintel in side wall
Douglas Fir #2 material
1.5 kPa snow load
R.O. – 1.8 m wide
Non-structural sheathing, 24” O.H.

Example 2: Find the lintel required

Two storey house, lintel on first storey in end wall
Spruce # 1 material
2.5 kPa snow load
R.O. – 2.2 m x 1.6 m
½” OSB sheathing, 12” O.H.

Review Questions

Use the NBC and Carpentry to answer the following:

Why is the supporting ribbon “let in” to the studs?
When is it permissible to use studs on the flat?
In load bearing exterior wall the minimum size of studs that may be used is _____.

a) 38 x 64 @ 400 mm

b) 38 x 89 @ 400 O.C.

c) 38 x 140 @ 400 O.C.

d) 38 x 140 @ 600 O.C.

When must studs be tripled at openings? How many of these are trimmers and full length studs?
Is the upper rough sill permitted to sit between the lintel and trimmers?
How do you calculate the length of lintels?
Double studs at openings shall be nailed with _____ mm nails spaced not more than _____ mm O.C.
Determine the minimum size of the lintel:

a) In a two-story house, a lintel is required to span a 7’-8” opening in the first floor exterior wall. What is the minimum size of the lintel? (Spruce no.1, snow load 1.5 kPa, non-structural sheathing, hip roof, 24” overhang)

b) If structural sheathing is used, what is the minimum size of the lintel?

Determine the lintel sizes for the following openings:

a) 6’ opening (Hem-Fir no. 2, snow load 2.0 kPa, 2 storey, non-structural sheathing, hip roof, lintel in end wall on first floor, 24” overhang)

b) Overhead door size 2.75 m x 3.048 m in 8 m x 24 m garage (Hem-Fir No.2, 3.0 kPa snow load, lintel supporting roof and ceiling only in side wall, 300 mm overhang)

Determine the following:

a) What size lintel is required for a window with a rough opening width of 1.9 m and a height of 0.94 m? (Hem-Fir No. 1, snow load 2.0 kPa, 2 storey non-structural sheathing, gable roof, lintel in side wall on first floor, 600 mm overhang)

b) What is the length of the cripples below the window? (Regular stud length 2353 mm, lintel tight to underside of top plate, no top sill)

What is the length of the trimmers and cripples?

36” x 42” window
92 5/8” studs
2×12 header, tight to top plate
Double top plate

Answers:

Provides better support for the second floor joists and provides a flush surface for finishes where the ceiling meets the exterior walls.
On non load-bearing walls where studs are spaced no more than 16” (400 mm) O.C. (9.23.10.3-2)
A
When the opening exceeds 3.0 m in width, 2 trimmers and 2 full length stud (9.23.10.6-1)
No
R.O. width + trimmers (76 if single trimmers, 152 if double trimmers)
76 mm, 750 mm O.C. (9.23.3.4)
1. 1. 2 – 38 x 286 (table 9.23.12.3-C)
  2. 2 – 38 x 235
1. 2 -38 x 184
2. 2 – 38 x 140
1. 2 – 38 x 286
2. 2029
Trimmers – 81 3/8”; Cripples – 36 3/8”

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Carpentry Refresher Program Manual Copyright © by Saskatchewan Indian Institute of Technologies-Trades and Industrial is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.