CCS Masonry & Mortar Repair Techniques 2 — Questions and Answers
Question 1: When repointing a chimney, how deep should old mortar be removed before applying new mortar?
- At least 3/4 inch (19mm) (Correct answer)
- At least 1/4 inch (6mm)
- At least 1/2 inch (13mm)
- At least 1 inch (25mm)
Correct answer: At least 3/4 inch (19mm)
NFPA 211 and masonry standards require removal of at least 3/4 inch of old mortar to ensure adequate bonding depth for new mortar.
Question 2: Which mortar type is most appropriate for repointing historic or older brick chimneys?
- Type S mortar
- Type N mortar (Correct answer)
- Type M mortar
- Type O mortar
Correct answer: Type N mortar
Type N mortar (1:1:6 ratio) is softer and more flexible, compatible with historic brick that can be damaged by the strength of Type S or M mortars.
Question 3: What is the primary cause of spalling brick on a chimney exterior?
- Excess soot buildup on the brick face
- Water penetration followed by freeze-thaw cycling (Correct answer)
- Overheating from excessive chimney fires
- Chemical reaction with flue gases
Correct answer: Water penetration followed by freeze-thaw cycling
Spalling occurs when water absorbed into the brick expands as it freezes, fracturing the brick face in repeated freeze-thaw cycles.
Question 4: A chimney technician notices mortar joints that are concave (slightly hollowed inward). This joint profile is called:
- Weathered joint
- Rodded or tooled joint (Correct answer)
- Raked joint
- Flush joint
Correct answer: Rodded or tooled joint
A rodded or tooled joint is formed by pressing a rounded tool into the mortar to create a concave profile that sheds water effectively.
Question 5: When mixing repointing mortar, which ingredient ratio describes Type S mortar?
- 1 part portland cement : 1 part lime : 6 parts sand
- 1 part portland cement : 1/2 part lime : 4.5 parts sand (Correct answer)
- 1 part portland cement : 0 lime : 3 parts sand
- 1 part portland cement : 2 parts lime : 9 parts sand
Correct answer: 1 part portland cement : 1/2 part lime : 4.5 parts sand
Type S mortar uses a 1:1/2:4.5 ratio of portland cement:lime:sand, providing high strength and good adhesion for below-grade and exterior applications.
Question 6: After applying new mortar during repointing, what is the recommended curing practice?
- Allow the mortar to dry as fast as possible in direct sunlight
- Mist the mortar with water and protect from direct sunlight for 3-7 days (Correct answer)
- Apply a sealant immediately after the mortar sets
- Cover with plastic sheeting to trap heat and speed drying
Correct answer: Mist the mortar with water and protect from direct sunlight for 3-7 days
Slow, moist curing for 3-7 days prevents premature drying and cracking, allowing the mortar to develop full strength.
Question 7: Which condition most clearly indicates that entire brick units need replacement rather than just repointing?
- Surface staining or efflorescence on the brick face
- Mortar joint voids greater than 1/4 inch deep
- Brick faces delaminating or structural cracking through the brick body (Correct answer)
- Hairline cracks in mortar joints only
Correct answer: Brick faces delaminating or structural cracking through the brick body
Delaminating brick faces or cracks passing through the brick body itself indicate structural failure of the masonry unit requiring replacement.
CCS Masonry & Mortar Repair Techniques 2
When repointing a chimney, how deep should old mortar be removed before applying new mortar?