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Floor Construction — ICC B2 Practice Questions

13 questions · 8% of the ICC B2 exam

Worked questions

1. Use 2021 IBC Table 2304.8(3) for wood structural floor panels at least 24 inches wide, continuous over at least two spans, with the strength axis perpendicular to supports and panel edges blocked. The uniform floor load is 50 psf, and no finish-floor span-increase exception is used. For sheathing-grade panels with a 24/16 span rating on supports spaced 16 inches on center, what is the smallest panel thickness listed in that row?

  • 7/16 inch
  • B3/8 inch
  • C3/4 inch
  • D1 inch

Where to look it up

https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042180/2021_International_Building_Code.pdf

Why A is correct

The 24/16 sheathing-grade row lists 7/16-inch and 1/2-inch panels and a 16-inch maximum floor span. Thus 7/16 inch is the smallest thickness listed for this specified row. Footnote c supplies the floor load and edge-support conditions; roof load columns are not the floor limits. This is not a universal thickness for every plywood floor. Source: 2021 IBC 2304.8.1 and Table 2304.8(3), including footnotes a and c, p. 23-12; https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042180/2021_International_Building_Code.pdf

2. Use 2021 IBC Table 2304.8(3) for wood structural floor panels at least 24 inches wide, continuous over at least two spans, with the strength axis perpendicular to supports and panel edges blocked. The uniform floor load is 50 psf, and no finish-floor span-increase exception is used. For single-floor-grade panels bearing a 16 o.c. span rating on supports spaced 16 inches on center, what is the smallest thickness listed for that rating?

  • A3/8 inch
  • B7/16 inch
  • 1/2 inch
  • D1 1/4 inches

Where to look it up

https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042180/2021_International_Building_Code.pdf

Why C is correct

The single-floor 16 o.c. row lists 1/2, 19/32 and 5/8 inch thicknesses. The smallest listed is 1/2 inch. The panel grade, rating, loading and support conditions govern this lookup; the depth of the supporting joist does not establish a universal 1 1/4-inch panel requirement. Source: 2021 IBC 2304.8.1 and Table 2304.8(3), including footnotes a, c and g, p. 23-12; https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042180/2021_International_Building_Code.pdf

3. A new commercial building in Climate Zone 3 uses the 2021 IECC Table C402.1.3 insulation R-value method. For a joist/framing floor in the building thermal envelope, what is the minimum insulation R-value in the Floors row?

  • AR-19
  • BR-25
  • R-30
  • DR-35

Where to look it up

https://www.iccsafe.org/wp-content/uploads/errata_central/2021-International-Energy-Conservation-Code-Errata-Complete.pdf

Why C is correct

The joist/framing floor row specifies R-30 for Climate Zone 3 for both Group R and all-other occupancies. This is an IECC envelope requirement, not a universal occupied-floor requirement in IBC 806.1.1. The question excludes mass floors, slabs-on-grade and alternative compliance paths. Source: ICC, 2021 IECC errata, corrected Table C402.1.3, PDF p.4; https://www.iccsafe.org/wp-content/uploads/errata_central/2021-International-Energy-Conservation-Code-Errata-Complete.pdf

4. For residential living-area floor framing eligible for the conventional provisions of 2021 IBC Section 2308, use Table 2308.4.2.1(2) with 40 psf live load and an L/360 deflection limit. No. 1 Douglas Fir-Larch joists will be spaced 16 inches on center with 10 psf dead load and an 18-foot span. Which is the smallest listed nominal size with a tabulated span sufficient for this span?

  • A2x6
  • B2x8
  • C2x10
  • 2x12

Where to look it up

https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042180/2021_International_Building_Code.pdf

Why D is correct

Under these specified conditions the tabulated maximum spans are 9 feet 11 inches for 2x6, 13 feet 1 inch for 2x8, 16 feet 5 inches for 2x10, and 19 feet 1 inch for 2x12. Only 2x12 reaches 18 feet. The result is specific to the stated species, grade, spacing and loads. Source: 2021 IBC 2308.4.2.1 and Table 2308.4.2.1(2), p. 23-38; https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042180/2021_International_Building_Code.pdf

5. For residential living-area floor framing eligible for the conventional provisions of 2021 IBC Section 2308, use Table 2308.4.2.1(2) with 40 psf live load and an L/360 deflection limit. No. 2 Southern Pine joists are spaced 16 inches on center with 10 psf dead load. Which is the smallest listed nominal size that permits a 14-foot span?

  • A2x6
  • B2x8
  • 2x10
  • D2x12

Where to look it up

https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042180/2021_International_Building_Code.pdf

Why C is correct

The specified row gives 9 feet 4 inches for 2x6, 11 feet 10 inches for 2x8, 14 feet for 2x10 and 16 feet 6 inches for 2x12. The smallest sufficient size is 2x10. This wood-joist selection uses the IBC wood span table, not the ACI structural-concrete code. Source: 2021 IBC 2308.4.2.1 and Table 2308.4.2.1(2), p. 23-38; https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042180/2021_International_Building_Code.pdf

6. An existing commercial building has a visibly sagging wood-framed floor. The observation alone has not established a cause. Which approach avoids prematurely diagnosing the problem?

  • AConclude that joist spacing alone proves the cause
  • Assess the framing, supports, bearing, connections, alterations and loading rather than treating subfloor damage as the only possible cause
  • CConclude that termite damage must be the cause before inspecting the members
  • DConclude that joist depth alone proves the cause

Where to look it up

https://www.huduser.gov/Publications/pdf/rehabinspect_2.pdf

Why B is correct

Sagging can result from several different mechanisms. HUD’s inspection guide, Section 4.7 (printed p.56), describes settlement, excessive spans, cut members, overloading and removed supports, and recommends checking support, bearing, connections and evidence of insect or fungal attack. These wood-framing diagnostic principles inform the approach here; that residential guide is not a commercial code requirement. IBC 2021 Section 1603.1 concerns structural construction documents, not a mandatory instruction to inspect the subfloor first. The observed sag alone does not identify a unique cause. Source: https://www.huduser.gov/Publications/pdf/rehabinspect_2.pdf

7 more in the bank

Answers and explanations for these are in the app.

  • A commercial building is being constructed with a floor drain. What is the minimum slope required for the floor drain according to the 2021 IBC?
  • A commercial building is being constructed with a floor that requires drainage. What is the minimum slope required for the floor according to the 2021 IBC?
  • A commercial building is being designed with a floor assembly that requires a fire rating of 1 hour. Which of the following fire-rated floor assemblies meets this requirement?
  • A commercial building is being modified to include a new floor above an existing floor. What is the minimum fire resistance rating required for the new floor assembly according to the 2021 IBC?
  • A commercial building is being used for a new occupancy that requires a higher load-bearing capacity. What is the minimum live load that the floor must be able to support according to the 2021 IBC?
  • During a renovation project, an existing floor requires the installation of a new opening. What is the maximum size of the opening allowed in a floor without additional structural reinforcement according to the 2021 IBC?
  • Which of the following R-values is required for the floor insulation in a commercial building according to the 2021 International Energy Conservation Code?

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