CFI CFI Post Setting & Foundation Work 2 — Questions and Answers
Question 1: Why is gravel placed at the bottom of a fence post hole before setting the post?
- To raise the post to the correct height
- To improve drainage and reduce rot at the post base (Correct answer)
- To save on concrete material costs
- To soften the impact if the post shifts
Correct answer: To improve drainage and reduce rot at the post base
A gravel layer at the base of the hole promotes drainage, keeping the post base drier and reducing wood rot and metal corrosion.
Question 2: When using a power auger to dig post holes, the operator should always:
- Call 811 to locate underground utilities before digging (Correct answer)
- Wear sandals for better ground feel
- Dig at maximum speed to reduce labor time
- Use the auger alone without a spotter
Correct answer: Call 811 to locate underground utilities before digging
Calling 811 (the national 'Call Before You Dig' number) to locate buried utilities is required by law before any excavation work in the US.
Question 3: What is the typical cure time for concrete post footings before attaching fence panels in normal weather?
- 1 hour
- 4 hours
- 24 to 48 hours (Correct answer)
- 7 days
Correct answer: 24 to 48 hours
Concrete post footings should cure for 24–48 hours before fence panels are attached to avoid disturbing the set and compromising footing strength.
Question 4: Which post material requires the use of ACQ-compatible (non-reactive) hardware?
- Vinyl posts
- Steel posts
- Pressure-treated lumber posts (Correct answer)
- Aluminum posts
Correct answer: Pressure-treated lumber posts
Pressure-treated lumber containing ACQ (Alkaline Copper Quaternary) is corrosive to standard steel fasteners, requiring hot-dipped galvanized or stainless steel hardware.
Question 5: When setting corner posts, why is it important to set them before line posts?
- Corner posts are lighter and easier to set
- They serve as reference points for aligning all intermediate posts (Correct answer)
- Building codes require corner posts first
- Concrete cures faster for corner locations
Correct answer: They serve as reference points for aligning all intermediate posts
Corner posts establish the fence layout's geometry and serve as fixed reference anchors so that a string line can be stretched to align all line posts accurately.
Question 6: What problem does adding too much water to concrete post footing mix cause?
- Faster cure time and excess strength
- Reduced workability and early cracking
- Increased compressive strength
- Reduced compressive strength and increased porosity (Correct answer)
Correct answer: Reduced compressive strength and increased porosity
Excess water raises the water-to-cement ratio, weakening the concrete matrix and creating a more porous footing that is vulnerable to freeze-thaw damage.
CFI CFI Post Setting & Foundation Work 2
Why is gravel placed at the bottom of a fence post hole before setting the post?