1. Weekend Cabin Retreat Project Sill and Floor Construction
Sacramento City College
EDT 300
Kenneth Fitzpatrick, P.E.
EDT Sill and Floor Construction

2. EDT 300 - Sill and Floor Construction
Objectives
Recognize platform and balloon framing.
Plan the appropriate floor support using joists or trusses for a structure.
Determine proper joist sizes using a typical span data chart.
Describe the components of a floor system.
EDT Sill and Floor Construction

3. EDT 300 - Sill and Floor Construction
Objectives
Demonstrate an understanding of the principles involved in post and beam construction.
EDT Sill and Floor Construction

4. EDT 300 - Sill and Floor Construction
Types of Framing
Methods of floor framing vary from one section of the country to another.
Builders in a given area may use different methods, based on personal preference and experience.
The basic types of floor framing are platform and balloon framing.
EDT Sill and Floor Construction

5. EDT 300 - Sill and Floor Construction
Platform Framing
Platform framing is popular for several reasons.
It can be used for both one- and two-story structures and is easy and fast to construct.
Shrinkage is uniform throughout the structure. A firestop is automatically provided.
Construction is safe because the work is performed on solid surfaces.
EDT Sill and Floor Construction

6. EDT 300 - Sill and Floor Construction
Platform Framing
In platform framing, the sill is the starting point in constructing a floor.
A sill is the lowest member of the frame of a structure,
Rests on the foundation
supports the floor joists or the uprights (studs) of the wall.
The sill in most residential construction is a 2 x 6.
(actual dimensions 1 1/2" x 5 1/2").
EDT Sill and Floor Construction

7. EDT 300 - Sill and Floor Construction
Platform Framing
Platform framing utilizes a method -of sill construction known as box sill construction.
The box sill consists of a 2 x 6 plate (also called a sill or mudsill) and a header that is the same size as the floor joists.
EDT Sill and Floor Construction

8. EDT 300 - Sill and Floor Construction

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14. EDT 300 - Sill and Floor Construction
Balloon Framing
Balloon framing was once used extensively, but in recent years has diminished in importance.
Its distinguishing feature is that the wall studs rest directly on the sill plate.
EDT Sill and Floor Construction

15. EDT 300 - Sill and Floor Construction
Balloon Framing
Two types of sill construction are used:
The solid or standard sill.
The T-sill.
The studs are nailed directly to the sill and joists in solid sill construction.
No header is used.
Joists are supported by a ribbon and nailed to the studs on the second floor level.
EDT Sill and Floor Construction

16. EDT 300 - Sill and Floor Construction
Balloon Framing
A firestop must be provided between the studs.
EDT Sill and Floor Construction

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Balloon Framing
In T-sill construction, a header is used, which also serves as a firestop.
The studs
Rest on the wall plate.
Are nailed to the header as well as the sill plate.
The sill may be very wide, to provide a good base for the joists to rest on.
Solid sill is used more extensively in two story homes.
EDT Sill and Floor Construction

18. Balloon Framing Advantages
Small potential shrinkage.
Vertical Stability.
Can be used for two-story homes with brick veneer or stucco exterior wall finishes.
EDT Sill and Floor Construction

19. Balloon Framing Disadvantages
A “less than desirable” surface to work on during construction.
Firestop blocks must be used.
EDT Sill and Floor Construction

20. EDT 300 - Sill and Floor Construction

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22. EDT 300 - Sill and Floor Construction
Joist and Beams
Joists provide support for the floor.
Usually made from a common soft wood such as
southern yellow pine
fir
larch
hemlock or spruce.
The size of floor joists ranges from a nominal size of 2 x 6 to 2 x 12.
Spacing from 12" to 24".
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23. EDT 300 - Sill and Floor Construction
Joist and Beams
The size joist required for a given situation will depend on the
length of space
load to be supported
specie and grade of wood
and distance the joists are spaced apart.
Spacing of floor joists may be 12, 16, or 24" o.c. (on center).
A spacing of 16" o.c. is most common.
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24. EDT 300 - Sill and Floor Construction
Joist and Beams
Span data for floor joists is presented in tables.
The span data presented assumes a maximum deflection of 1/360th of the span with a normal live load.
This is the amount which most codes require.
The normal live load is 40 pounds per square foot.
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25. EDT 300 - Sill and Floor Construction
Floor Systems
A floor system may also be constructed using girders or trusses
usually 4 x 6, 4 x 8, or 4 x 10 depending on the span) in the place of floor joists.
The purpose of this approach is to use fewer support members (joists).
The typical spacing of girders or trusses in this system is 48" o.c. with 1 1/8" thick tongue-and-groove plywood as the floor decking.
EDT Sill and Floor Construction

26. EDT 300 - Sill and Floor Construction
Floor Systems
The distance which joists must span is usually so great that a beam or load-bearing wall is needed to reduce the span.
The beam may be
a solid timber
a built-up beam from dimension lumber
a metal S-beam.
Load-bearing walls may be concrete block, cast concrete, or frame construction.
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Floor Systems
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Floor Systems
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Floor Systems
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Floor Systems
Partition walls that are supported by the floor joists require added support.
It is good practice to double the joists under parallel partition walls.
If space between the joists is used as a cold air duct, solid blocking is used between the joists.
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31. EDT 300 - Sill and Floor Construction
Floor Systems
Openings in the floor for stairs and chimneys require double joist framing.
EDT Sill and Floor Construction

32. EDT 300 - Sill and Floor Construction
Floor Systems
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33. EDT 300 - Sill and Floor Construction
Floor Systems
Cross bridging is commonly used to stiffen the floor and spread the load over a broader area.
Bridging boards are ordinarily 1 " x 3" in size with the ends cut at an angle so they fit snugly against the joist.
They are nailed securely in place midway between the beam and wall.
Metal bridging is also available.
EDT Sill and Floor Construction

34. EDT 300 - Sill and Floor Construction
Floor Systems
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35. EDT 300 - Sill and Floor Construction
Floor Systems
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36. EDT 300 - Sill and Floor Construction
Floor Trusses
Engineered wood floor trusses for light-frame construction are widely used for residential structures.
minimum of depth
lightweight assembly
easy to handle.
The open web construction reduces transmission of sound through floor/ceiling assemblies.
Makes installation of plumbing, heating, and electrical systems easy.
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37. EDT 300 - Sill and Floor Construction
Floor Trusses
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38. EDT 300 - Sill and Floor Construction
Floor Trusses
Computers are used to design modern engineered floor trusses to assure load capabilities for a given design.
Each truss has a built-in camber so that the floor/ceiling will be level once a load is applied.
Stress-graded lumber is used in their construction so that a minimum amount of material is required.
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39. EDT 300 - Sill and Floor Construction
Floor Trusses
Some trusses are fabricated with lumber chords and patented galvanized steel webs, instead of the typical wood webs.
The webs have metal teeth which are pressed into the sides of the chords.
A reinforcing rib withstands both tension and compression forces.
Engineered wood floor trusses are usually fabricated from 2 x 4 or 2 x 6 lumber and generally spaced 24" o.c.
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Floor Trusses
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41. EDT 300 - Sill and Floor Construction
Subfloor
Plywood, tongue-and-groove boards, common boards, and other panel products are used for subfloors.
Plywood is advantageous.
large size of plywood
short time required to nail the sheets in place
EDT Sill and Floor Construction

42. Other Subfloor Materials
One-half inch thick plywood
Composite board
Waferboard
Oriented strand broad
Structural particleboard,
These be used when joists are spaced 16" o.c.
Some builders prefer 5/8 in. stock.
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43. Other Subfloor Materials
When these products are used, the joist spacing must be is very accurate.
All edges of the panels must be supported.
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44. Other Subfloor Materials
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45. EDT 300 - Sill and Floor Construction
Subfloor Materials
Some localities combine the subfloor and underlayment (usually 5/8"particleboard) into a single thickness that is generally 1 1/8" thick.
The sheets have tongue-and-groove edges and require no blocking between the joists.
A single thickness sheet of 3/4" tongue-and-groove plywood may also be used for some applications.
EDT Sill and Floor Construction

46. EDT 300 - Sill and Floor Construction
Subfloor Materials
Plywood should be installed with the grain direction of the outer plies at right angles to the joists.
It is stronger when positioned in this manner.
Panel products should also be staggered so that end joints in adjacent panels break at different joists.
A slight space must be allowed between sheets for expansion.
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47. EDT 300 - Sill and Floor Construction
Subfloor Materials
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48. EDT 300 - Sill and Floor Construction
Subfloor Materials
Subfloor panels may also be glued and nailed to the joists.
Structural tests have shown that stiffness is increased by 25 percent with 2 x 6 joists and 5/8" plywood.
Gluing advantage
squeak-free structure
eliminates nail-popping
reduces labor costs.
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49. EDT 300 - Sill and Floor Construction
Cantilevered Joists
Home designs where a section of the floor projects beyond a lower level are called cantilevered joists.
These joists are parallel to the overhanging area
EDT Sill and Floor Construction

50. EDT 300 - Sill and Floor Construction
Cantilevered Joists
Rule of thumb for necessary length of cantilevered joists:
Extend the joists inside at least twice the distance they overhang outside.
If the inside distance is too short the floor may sag along the outside wall.
If a ledger strip is used, locate it along the top of the inside double header joist since the force will be up rather than down.
EDT Sill and Floor Construction

51. EDT 300 - Sill and Floor Construction
Cantilevered Joists
EDT Sill and Floor Construction

52. Framing Under Slate or Tile
Areas which have ceramic tile, slate, or stone floors require a substantial base.
If a concrete base is provided, the floor framing must be lowered to provide for the concrete.
EDT Sill and Floor Construction

53. Framing Under Slate or Tile
Several techniques are used:
A smaller size joist may be used and the space between joists reduced to provide adequate support.
This is a common solution to the problem.
Another technique is to use one or more beams under the section to support the added weight.
The dead weight may be as much as 40 or 50 pounds per square foot in a bathroom with a tile floor and heavy fixtures.
EDT Sill and Floor Construction

54. Framing Under Slate or Tile
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55. Framing Under Slate or Tile
The concrete base for the tile or stone should be
reinforced with wire mesh
cast on a plywood subfloor covered with building paper.
A special type of concrete is generally used. a mixture of 1 part portland cement and 6 parts sand, known as a cement mortar mix.
EDT Sill and Floor Construction

56. Post and Beam Construction
Large framing members (posts, beams, planks) are spaced farther apart than conventional framing members
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57. Post and Beam Construction
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58. Post and Beam Construction
Post and beam construction provides a greater freedom of design than conventional framing techniques.
The system is basically simple, but presents problems related to
larger structural sizes
framing connectors
methods of joinery.
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59. Post and Beam Construction
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60. Post and Beam Construction
Most of the weight is carried by the posts.
The walls are called curtain walls.
Curtain walls provide for wide expanses of glass without the need for headers.
EDT Sill and Floor Construction

61. Post and Beam Construction
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62. Post and Beam Construction
Wide overhangs are also possible by extending the large beams to the desired length.
Spacing of the posts is determined by the design of the building and the load to be supported.
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63. Post and Beam Construction
The foundation for a post and beam structure may be
a continuous wall
a series of piers where each post is to be located.
Size of footings will be determined by
the weight to be supported
soil bearing capacity
local building codes.
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64. Post and Beam Construction
The size of posts required will be at least 4" x 4".
If the floor is also to be supported by the posts, they should be at least 6" x 6".
Vertical height of the posts will be a factor in determining the size.
Again check local codes.
EDT Sill and Floor Construction

65. Post and Beam Construction
Beams may be solid, laminated, reinforced with steel, or plywood box beams.
Spacing and span of the beams will be determined by the size and kind of materials and load to be supported.
In most normal situations, a span of 7'-O" may be used when 2" thick tongue-and-groove subfloor or roof decking is applied to the beams.
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66. Post and Beam Construction
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67. Post and Beam Construction
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68. Post and Beam Construction
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69. Post and Beam Construction
Thicker beams must be used if a span greater than 7'-O" is required.
Two systems of beam placement are possible with post and beam construction.
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70. Post and Beam Construction
First system: the longitudinal method.
Beams are placed at right angles to the roof slope.
Roof decking is laid, therefore from the ridge pole to the eaves line.
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71. Post and Beam Construction
Second system: the transverse method.
The beams follow the roof slope and decking runs parallel to the roof ridge.
A post and beam structure has a limited number of joints.
Fastening small members by nailing does not provide a satisfactory connection.
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72. Post and Beam Construction
Metal plates or connectors are used.
These are fastened with lag screws or bolts.
Decking planks for the roof and floor range in thickness from 2 to 4 inches.
The planks are usually tongue-and-grooved along the edges and they may be tongue-and-grooved on the ends as well.
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73. Post and Beam Construction
It is customary to leave the underside of the planked roof exposed.
If added insulation is required, it may be placed above the decking and under the roofing material.
Rigid type insulation should be used.
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74. Post and Beam Construction
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EDT Sill and Floor Construction