1. Information related to Chapter 7 in the textbook
Floor Framing
Information related to Chapter 7 in the textbook

2. Floor Framing
Floor systems are based on platform framing, however for many years balloon framing was used. Platform framing:
Allows 3 or more stories to be built from short (8’) lumber.
Safe fire construction
Wall height fits modular materials (4x8 sheathing)
Uses least expensive lumber

3. Floor Framing
Balloon framing used from mid 1800s to mid 1900s. Balloon framing:
Builds first and second story walls at once, and hangs floor on the side
Allowed fire to travel quickly in walls
Required good quality 16’wood
Walls were typically sheathed with solid boards

4. Floor Framing Components of a Platform Frame
Sill plate (also sill, mudsill)
Girder (Beam, Built-up beam)
Floor joists
Bridging
Sheathing (Subfloor)

5. Floor Framing
Sill is bolted to the foundation, and the floor joists are nailed to the sill.
The subflooring is nailed to the joists to create the deck, or platform on which the walls are built.

6. Floor Framing
Sills – Pressure treated lumber that is bolted to the foundation. Anchor bolts set every 4’, 6’, or 8’ apart. Can be leveled if foundation is not level, and sealed with seal sealer or caulk.
Girders – For floors that span more than 16’, the center of the floor typically rests on a girder. Girders are made of Steel, LVL, or built-up from solid sawn wood. The size of the girder is usually called out on the plans.

7. Floor Framing Floor Joists – Selection based on 4:
Span – The distance between the supports
Load and Deflection– 40 psf Live load, 10 psf Dead load typical for all areas except 2nd floor bedrooms ( 30 psf LL, 10 psf DL). L/360 typical limit for deflection for floors.
On-center spacing – 12,16,19.2, or 24”
Size of lumber - 2x6, 2x8,2x10,2x12
Species and grade - #2 SPF and #2 Hem Fir are the most common grades found in the Northeast.
Span tables available on-line from Canadian Wood Council

8. Floor Framing
On-center spacings – The floor joists must be located so that both edges of an 8’ (96”) sheet of plywood are supported. Possible spacings include 12”, 16”, 19.2”, and 24”. When starting to layout joists from the edge of the floor, the spacings are determined as follows:

9. Floor Framing Special framing-
Extra framing is included around openings in the floors for stairs, chimneys, mechanical ducts.
Extra framing is included under walls parallel to the joists, bathtubs, etc.
Cantilevered joists are modified to ensure adequate support.
Bridging installed on joists over 8’
Cutting of joists for duct work, chases, pipes, etc.

10. Floor Framing
Framing for openings: The joists on each side of are doubled to increase support for the floor. Members perpendicular to the joists are Headers and parallel to the joists are Trimmers. Locations where full joists would have been placed are filled with tail joists

11. Floor Framing

12. Floor Framing
Cantilevered joists – Used for bay windows, second and third floor decks, steep slope sites.
Joists should extend back into framing twice the distance they extend out.
Blocking (not bridging) is installed between joists at the point of the support

13. Floor Framing
When a wall runs parallel to the joists (and below a bathtub) the joists are doubled to provide extra support. Space between joists allows room for electrical, plumbing, etc. Walls which are load bearing must have a girder or wall below them.

14. Floor Framing
Bridging – Is used to support floor joists to keep them from twisting under load (lateral torsional buckling), and to provide some load sharing. Used at the center of spans over 8’. Bridging should be nailed off after subflooring is down.
Three types of bridging
Wood cross-bridging
Wood solid bridging
Metal cross-bridging

15. Floor Framing
Cutting joists – As soon as the carpenter installs the joists, the other trades (electrical, plumbing, HVAC, etc) begin cutting into them. The holes must not substantially weaken the joist. This is especially critical when working with I-joists.

16. Floor Framing
I joists and open web joists (parallel chord truss) – Home Design is emphasizing large open spaces without dividing walls (“Open plan”) This often requires joists to span distances greater than 20’. For long spans 24’-32’ engineered wood products are very popular

17. Floor Framing Headline from Pompey fire
Joists must be installed according to manufacturer’s instructions, and no modifications can be made without the approval of a registered professional.
Headline from Pompey fire

18. Floor Framing

19. Floor Framing
Tongue and Groove subflooring – Subflooring should be installed with construction adhesive (20% stronger, less squeaks) and following proper nailing schedule. Some T&G subfloor is sized for spacing. Thickness determined based on span rating.
Available in both veneered plywood and composite.
Sanded subfloor-underlayment popular in tract construction.