RRT Subfloor Preparation & Assessment 1 — Questions and Answers
Question 1: What is the maximum allowable moisture vapor emission rate (MVER) for a concrete subfloor before installing carpet with standard adhesive?
- 3 lbs per 1,000 sq ft per 24 hours
- 5 lbs per 1,000 sq ft per 24 hours (Correct answer)
- 8 lbs per 1,000 sq ft per 24 hours
- 10 lbs per 1,000 sq ft per 24 hours
Correct answer: 5 lbs per 1,000 sq ft per 24 hours
Industry standards (ASTM F1869) generally set 5 lbs/1,000 sq ft/24 hours as the maximum MVER for adhesive carpet installations on concrete.
Question 2: When assessing a wood subfloor for carpet reinstallation, what is the maximum acceptable deflection under a concentrated 200-lb load?
- L/180
- L/240
- L/360 (Correct answer)
- L/480
Correct answer: L/360
L/360 is the standard deflection limit for subfloors receiving hard or resilient flooring; carpet installations follow the same structural guideline.
Question 3: Which test method uses a calcium chloride dish sealed to a concrete slab to measure moisture emissions?
- ASTM F2170
- ASTM F1869 (Correct answer)
- ASTM D4263
- ASTM E1745
Correct answer: ASTM F1869
ASTM F1869 is the Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride.
Question 4: A concrete subfloor has a pH reading of 10. What does this indicate for carpet installation?
- The slab is neutral and ready for installation
- The slab is too acidic and must be treated
- The slab is highly alkaline and may affect adhesive bond (Correct answer)
- The slab pH is irrelevant to carpet installation
Correct answer: The slab is highly alkaline and may affect adhesive bond
A pH above 9 indicates high alkalinity, which can break down adhesives and adhesive bonds, requiring mitigation before installation.
Question 5: What is the recommended flatness tolerance for a concrete subfloor prior to carpet installation?
- 1/4 inch in 6 feet
- 3/16 inch in 10 feet (Correct answer)
- 1/8 inch in 6 feet
- 1/2 inch in 10 feet
Correct answer: 3/16 inch in 10 feet
CRI (Carpet and Rug Institute) and most manufacturers specify no more than 3/16 inch variation in 10 feet for subfloor flatness.
Question 6: Which of the following is the correct procedure when a wood subfloor has protruding nail heads before carpet installation?
- Sand the entire subfloor smooth
- Pull the nails and refill the holes
- Set the nail heads below the surface with a nail set (Correct answer)
- Leave them and use extra padding to cushion
Correct answer: Set the nail heads below the surface with a nail set
Protruding nail heads must be set below the surface so they do not telegraph through the carpet or damage it over time.
Question 7: When evaluating a subfloor that shows cupping in wood planks, what is the primary cause of this condition?
- Excessive foot traffic over time
- Moisture imbalance between the top and bottom face of the plank (Correct answer)
- Low-quality lumber used during construction
- Improper carpet padding beneath the boards
Correct answer: Moisture imbalance between the top and bottom face of the plank
Cupping occurs when the bottom face of a wood plank absorbs more moisture than the top face, causing the edges to rise above the center.
RRT Subfloor Preparation & Assessment 1
What is the maximum allowable moisture vapor emission rate (MVER) for a concrete subfloor before installing carpet with standard adhesive?