Comprehensive Exam Preparation
Based on International Residential Code (IRC)
Foundation and Footings (Questions 1-30)
Q1. What is the minimum depth for footings below undisturbed ground
surface in non-frost areas?
ANSWER : 12 inches below undisturbed ground surface (IRC R403.1.4)
,Q2. What is the minimum width of concrete or masonry footings for one-
story wood frame construction?
ANSWER : 12 inches (IRC Table R403.1)
Q3. What is the minimum thickness of footings?
ANSWER : 6 inches for concrete footings (IRC R403.1)
Q4. What is the minimum compressive strength for concrete used in
footings?
ANSWER : 2,500 psi (IRC R402.2)
Q5. Where is stepped footing required?
ANSWER : When a foundation is located on sloped ground and exceeds
24 inches difference in height (IRC R403.1.5)
Q6. What is the minimum depth for frost-protected footings?
ANSWER : Must extend below the frost line or a minimum of 12 inches
below undisturbed ground (varies by location)
Q7. What is the minimum reinforcement for concrete footings?
ANSWER : One #4 bar top and bottom for footings supporting two stories
or more (IRC R403.1.3)
Q8. What is the maximum slope permitted without requiring stepped
footings?
ANSWER : Slopes greater than one unit vertical in ten units horizontal
(10%) (IRC R403.1.5)
Q9. What is the minimum bearing capacity required for supporting soils?
ANSWER : 1,500 psf for continuous footings (varies by soil type - IRC
Table R401.4.1)
Q10. What is required when footings bear on fill material?
ANSWER : Fill must be properly compacted and approved by the building
official (IRC R401.4)
Q11. What is the minimum projection of footing beyond foundation wall?
ANSWER : 2 inches minimum, 1/3 of wall thickness maximum (IRC
R403.1)
,Q12. What is required for footings on expansive soils?
ANSWER : Special design in accordance with IRC R401.4.2 or
engineered foundation
Q13. What is the minimum clear cover for reinforcement in concrete
footings?
ANSWER : 3 inches when placed against earth (IRC R403.1.3.2)
Q14. What is required for gravel or crushed stone footings?
ANSWER : Minimum 8 inches thick, extending 6 inches beyond foundation
wall (IRC R403.4)
Q15. What is the maximum vertical step in stepped footings?
ANSWER : Not to exceed 2 feet (IRC R403.1.5)
Q16. What is required for footing drainage?
ANSWER : Drain tile or perforated pipe around footings when required
(IRC R405.1)
Q17. What is the minimum size of drain tile?
ANSWER : 4-inch diameter (IRC R405.1)
Q18. Where must footing drains discharge?
ANSWER : To approved drainage system or daylight (IRC R405.1)
Q19. What is required beneath footings in areas with wood-destroying
insects?
ANSWER : Soil treatment or physical barrier against termites (IRC
R318.2)
Q20. What is the minimum depth of fill under floor slabs?
ANSWER : 4 inches of approved fill material (IRC R506.2.1)
Q21. What type of concrete mix is required for footings?
ANSWER : Minimum 2,500 psi compressive strength at 28 days (IRC
R402.2)
Q22. What is required when footings support permanent wood
foundations?
, ANSWER : Gravel or crushed stone base, 4-inch minimum thickness (IRC
R403.2)
Q23. What is the minimum lap length for footing reinforcement?
ANSWER : 40 bar diameters for #4 and #5 bars (IRC R403.1.3.2)
Q24. What is required for footings in seismic design categories D0, D1, and
D2?
ANSWER : Continuous reinforcement per IRC R403.1.3.1
Q25. What is the minimum width for masonry stem walls?
ANSWER : 6 inches (IRC Table R404.1.1(1))
Q26. When is a foundation investigation required?
ANSWER : When required by building official for questionable soil
conditions (IRC R401.4)
Q27. What is the maximum slope of backfill against foundation walls?
ANSWER : Slope away from foundation at minimum 5% for 10 feet (IRC
R401.3)
Q28. What is required for wood in contact with concrete foundations?
ANSWER : Pressure-preservative treated or naturally durable species
(IRC R317.1)
Q29. What is the minimum thickness of foundation walls?
ANSWER : 6 inches for masonry, 5.5 inches for concrete (IRC R404.1)
Q30. What is required when a footing is located near an existing footing?
ANSWER : Must not be placed closer than 45-degree angle from bottom
of existing footing unless engineered (IRC R403.1.8)
Based on International Residential Code (IRC)
Foundation and Footings (Questions 1-30)
Q1. What is the minimum depth for footings below undisturbed ground
surface in non-frost areas?
ANSWER : 12 inches below undisturbed ground surface (IRC R403.1.4)
,Q2. What is the minimum width of concrete or masonry footings for one-
story wood frame construction?
ANSWER : 12 inches (IRC Table R403.1)
Q3. What is the minimum thickness of footings?
ANSWER : 6 inches for concrete footings (IRC R403.1)
Q4. What is the minimum compressive strength for concrete used in
footings?
ANSWER : 2,500 psi (IRC R402.2)
Q5. Where is stepped footing required?
ANSWER : When a foundation is located on sloped ground and exceeds
24 inches difference in height (IRC R403.1.5)
Q6. What is the minimum depth for frost-protected footings?
ANSWER : Must extend below the frost line or a minimum of 12 inches
below undisturbed ground (varies by location)
Q7. What is the minimum reinforcement for concrete footings?
ANSWER : One #4 bar top and bottom for footings supporting two stories
or more (IRC R403.1.3)
Q8. What is the maximum slope permitted without requiring stepped
footings?
ANSWER : Slopes greater than one unit vertical in ten units horizontal
(10%) (IRC R403.1.5)
Q9. What is the minimum bearing capacity required for supporting soils?
ANSWER : 1,500 psf for continuous footings (varies by soil type - IRC
Table R401.4.1)
Q10. What is required when footings bear on fill material?
ANSWER : Fill must be properly compacted and approved by the building
official (IRC R401.4)
Q11. What is the minimum projection of footing beyond foundation wall?
ANSWER : 2 inches minimum, 1/3 of wall thickness maximum (IRC
R403.1)
,Q12. What is required for footings on expansive soils?
ANSWER : Special design in accordance with IRC R401.4.2 or
engineered foundation
Q13. What is the minimum clear cover for reinforcement in concrete
footings?
ANSWER : 3 inches when placed against earth (IRC R403.1.3.2)
Q14. What is required for gravel or crushed stone footings?
ANSWER : Minimum 8 inches thick, extending 6 inches beyond foundation
wall (IRC R403.4)
Q15. What is the maximum vertical step in stepped footings?
ANSWER : Not to exceed 2 feet (IRC R403.1.5)
Q16. What is required for footing drainage?
ANSWER : Drain tile or perforated pipe around footings when required
(IRC R405.1)
Q17. What is the minimum size of drain tile?
ANSWER : 4-inch diameter (IRC R405.1)
Q18. Where must footing drains discharge?
ANSWER : To approved drainage system or daylight (IRC R405.1)
Q19. What is required beneath footings in areas with wood-destroying
insects?
ANSWER : Soil treatment or physical barrier against termites (IRC
R318.2)
Q20. What is the minimum depth of fill under floor slabs?
ANSWER : 4 inches of approved fill material (IRC R506.2.1)
Q21. What type of concrete mix is required for footings?
ANSWER : Minimum 2,500 psi compressive strength at 28 days (IRC
R402.2)
Q22. What is required when footings support permanent wood
foundations?
, ANSWER : Gravel or crushed stone base, 4-inch minimum thickness (IRC
R403.2)
Q23. What is the minimum lap length for footing reinforcement?
ANSWER : 40 bar diameters for #4 and #5 bars (IRC R403.1.3.2)
Q24. What is required for footings in seismic design categories D0, D1, and
D2?
ANSWER : Continuous reinforcement per IRC R403.1.3.1
Q25. What is the minimum width for masonry stem walls?
ANSWER : 6 inches (IRC Table R404.1.1(1))
Q26. When is a foundation investigation required?
ANSWER : When required by building official for questionable soil
conditions (IRC R401.4)
Q27. What is the maximum slope of backfill against foundation walls?
ANSWER : Slope away from foundation at minimum 5% for 10 feet (IRC
R401.3)
Q28. What is required for wood in contact with concrete foundations?
ANSWER : Pressure-preservative treated or naturally durable species
(IRC R317.1)
Q29. What is the minimum thickness of foundation walls?
ANSWER : 6 inches for masonry, 5.5 inches for concrete (IRC R404.1)
Q30. What is required when a footing is located near an existing footing?
ANSWER : Must not be placed closer than 45-degree angle from bottom
of existing footing unless engineered (IRC R403.1.8)
