Structure Inspection Section#2 Floors Quiz#4

You should have finished Study Session 3 and Quick Quiz 3 before starting this Study Session. This Study Session covers joists.

The estimated completion time is one hour.

Objectives
At the end of this study session, you should be able to:

• List two joist materials and seven types of floor joists and trusses.
• Explain in one sentence how joists can support masonry walls.
• Explain in one sentence fire-cut joists.
• Explain in one sentence why joists should be laid crown up.
• Explain in one sentence rim joists.
• List twelve common joist problems.
• List twelve problems common to engineered wood floor systems.

How does a ledger board support joists?

The ledger board is fastened to the beam near the bottom and the joist rests on the top of the ledger board.

Joist sag may be the result of - (4 answers)

1. Overspanning

2. Joists weakened by rot, insect attack, notches, holes, fire damage

3. Joists installed crown down

4. Concentrated loads

List 12 common joist problems you will see on inspections.

1. rot and insect damage

2. sagging joists (often part of a springy floor)

3. poor end bearing

4. rotated or twisted joists

5. no blocking, bridging or strapping

6. inappropriate notching or holes

7. split or damaged

8. weak cantilevers

9. weakness created by openings around stairs, chimneys and windows

10. prior repairs

11. concentrated loads

12. missing joists

List eight common engineered wood flooring problems.

1. Holes too big or in the wrong place 
2. Incorrect joist hangers 
3. Improper rim joist material 
4. Missing or incomplete blocking 
5. Split, notched or cut flanges 
6. Inadequate end-bearing 
7. Joists bevelled or fire-cut 
8. Inadequate blocking on laminated I-joists 
9. Inadequate bridging or load-sharing 
10. Trusses that are either too long or too short 
11. Concentrated loads on the top of trusses 
12. Trusses installed upside down

List four things that can prevent joist twisting.

1. Strapping

2. cross-bridging

3. Solid blocking

4. Drywall or plaster ceilings

List six possible joist hanger problems

1. Undersized 
2. Inadequate nails 
3. Wrong type of nails 
4. Joist not bottomed in hanger 
5. Joist doesn't penetrate fully into hanger 
6. Joists connected to beam at other than 90 degrees with conventional hanger. 
7. Doubled joists connected to beam with single joist hanger

Name five engineered wood products that may replace conventional joists.

1. Trusses 
2. Plywood 
3. Wood I-joists 
4. Laminated Veneer Lumber (LVL) 
5. Parallel Strand Lumber (PSL) 
6. Laminated Strand Lumber (LSL)

Outdoor cantilevers are particularly vulnerable to moisture damage. Where is the problem most likely to occur and why?

The problem is most likely to occur where the joists pass through the walls because this is the area that is likely to stay wet.

Roughly how far can these common joists span if spaced 16 inches apart? 2 x 8? 2 x 10? 2 x 12?

2x6 can span about 9 feet

2x8 can span about 12 feet

2x10 can span about 14 feet

2x12 can span about 16 feet

The joist resting on a beam should not extend past the beam more than 2 inches. Why?

The end of the joist may kick up, creating a high spot in the floor.

What is a cantilever?

The member is supported at one end and partway along the length. One end is unsupported.

Joists typically need ___ inches of end bearing. (Insert a number).

1-1/2 inch

Possible functions of bridging and blocking are - (3 answers)

reduce joist spacing

prevent joist twisting

vibration damping

The function of joists is to: (three answers)

transfer live loads to beams

transfer dead loads to foundations

transfer live loads to walls

Fire-cutting joists is a serious structural error.

False

Holes in joists should be near the bottom rather than the middle of the joists.

False

Joists are often used to provide lateral support for solid masonry walls.

True

Joists notched at their end are stronger than normal joists

False

Joists resting on foundation walls at or near grade level are prone to rot.

True

Joists see vertical loads only.

False

Partition walls exert no load on floor joists because they are not load bearing walls.

False