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Nevada C-17 Lathing & Plastering
Contractor Exam Practice Test Questions
And Correct Answers (Verified Answers)
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- What is the primary purpose of lath in plaster construction? A. To provide insulation B. To support electrical wiring C. To provide a mechanical base for plaster adhesion D. To waterproof the wall Rationale: Lath creates a bonding surface that allows plaster to adhere securely to the structure.
- Which type of lath is most commonly used in modern construction? A. Wood lath B. Stone lath C. Metal lath D. Clay lath Rationale: Metal lath is preferred today due to strength, durability, and compatibility with modern plaster systems.
- What is the standard mix ratio for scratch coat plaster? A. 1:1: B. 1:5 cement-sand
C. 1:3 cement-sand D. 1:8 cement-sand Rationale: A 1:3 mix provides sufficient strength and bonding for scratch coats.
- The scratch coat is primarily used to: A. Provide final finish B. Prevent cracking only C. Create a bonding surface for the brown coat D. Seal moisture Rationale: The scratch coat is roughened to help the next layer adhere.
- What tool is used to scratch the first coat of plaster? A. Float B. Trowel C. Scarifier or scratch comb D. Hawk Rationale: A scratch tool creates grooves that improve bonding of the next coat.
- Which coat provides leveling in a three-coat plaster system? A. Finish coat B. Scratch coat C. Brown coat D. Bond coat Rationale: The brown coat levels the surface before finishing.
- What is the main ingredient in gypsum plaster? A. Lime B. Sand C. Cement D. Calcium sulfate hemihydrate Rationale: Gypsum plaster is made from calcium sulfate hemihydrate.
Rationale: Control joints allow expansion and contraction without cracking. 13.What is the minimum thickness of a scratch coat? A. 1/8 inch B. 1/4 inch C. 3/8 inch D. 1 inch Rationale: Scratch coats typically require adequate thickness for bonding strength. 14.Which plaster type sets fastest? A. Lime plaster B. Cement plaster C. Gypsum plaster D. Clay plaster Rationale: Gypsum sets faster than cement or lime-based plasters. 15.What is the function of bonding agents? A. Reduce cost B. Add color C. Improve adhesion between surfaces and plaster D. Increase water resistance only Rationale: Bonding agents enhance adhesion between layers. 16.What causes plaster delamination? A. Too much sand B. Excess curing C. Poor surface preparation D. High humidity Rationale: Dirty or smooth surfaces prevent proper bonding. 17.Which material is used in stucco? A. Clay only B. Gypsum only
C. Cement, sand, lime, and water D. Wood fibers Rationale: Stucco is a cement-based exterior plaster mix. 18.What is the purpose of a brown coat? A. Waterproofing B. Decoration C. Leveling and strengthening base coat D. Coloring Rationale: It creates a smooth, level surface for finish coat. 19.What is the typical curing time for cement plaster? A. 1 day B. 2 days C. 7 days minimum D. 30 days Rationale: Cement plaster requires adequate curing for strength development. 20.What happens if plaster is applied too thick in one coat? A. Improved bonding B. Faster drying C. Cracking and shrinkage D. Better insulation Rationale: Thick applications cause uneven drying and cracking. 21.What is the function of water in plaster mix? A. Color B. Strength only C. Hydration and workability D. Hardening agent Rationale: Water activates cement/gypsum and improves application. 22.Which surface requires bonding agent before plastering? A. Raw wood
B. Gypsum finish C. Cement stucco finish D. Clay finish Rationale: Cement stucco resists weather conditions best. 28.What is the main cause of blistering in plaster? A. Cold weather B. Too little sand C. Trapped air or moisture D. Excess curing Rationale: Air pockets expand and create blisters. 29.What is key for proper plaster adhesion? A. Smooth surface B. Dry surface only C. Clean, roughened surface D. Painted surface Rationale: Rough surfaces improve mechanical bonding. 30.What is the purpose of mesh in plastering? A. Decoration B. Coloring C. Reinforcement and crack prevention D. Insulation Rationale: Mesh strengthens plaster and reduces cracking. 31.Which is a common plaster failure? A. Expansion B. Hardening C. Cracking D. Melting Rationale: Cracking is one of the most frequent defects. 32.What is used to check surface level? A. Plumb bob
B. Trowel C. Spirit level D. Float Rationale: Spirit levels ensure flatness and alignment. 33.What is the role of lime in plaster? A. Color B. Speed setting C. Workability and flexibility D. Hardening Rationale: Lime improves plasticity and reduces cracking. 34.What is the first step before plastering? A. Painting B. Drying wall C. Surface preparation and cleaning D. Polishing Rationale: Clean surfaces ensure proper bonding. 35.Which condition is best for plaster curing? A. Hot dry wind B. Direct sunlight C. Moist, controlled conditions D. Freezing temperatures Rationale: Moist curing prevents rapid drying and cracking. 36.What causes hollow sounding plaster? A. Over curing B. Too much sand C. Poor adhesion to substrate D. Excess lime Rationale: Detachment creates hollow voids. 37.What is the function of a hawk in plastering? A. Cutting metal
B. Low humidity C. Moisture movement through material D. Too much sand Rationale: Water carries salts to surface as it evaporates. 43.What is the function of a plumb bob? A. Measure thickness B. Level horizontal surfaces C. Check vertical alignment D. Mix plaster Rationale: It ensures walls are vertically straight. 44.What is required for exterior plaster durability? A. Soft sand only B. Thin coating C. Proper mix ratio and curing D. No curing Rationale: Correct mix and curing ensure long-term durability. 45.What causes cracking at joints? A. Too much water B. Over curing C. Lack of control joints or movement allowance D. Excess sand Rationale: Movement without joints causes stress cracks. 46.What is the function of primer before plaster? A. Decoration B. Cooling C. Improves adhesion and sealing D. Strength reduction Rationale: Primers enhance bonding and reduce absorption. 47.What is key safety equipment for plastering? A. Gloves only
B. Helmet only C. Gloves, goggles, and scaffolding safety gear D. None Rationale: PPE protects workers from dust and falls. 48.What is the purpose of curing compounds? A. Speed drying B. Color plaster C. Retain moisture during curing D. Increase sand Rationale: They reduce water evaporation. 49.What causes uneven plaster texture? A. Too much lime B. Good mixing C. Poor application technique D. Proper curing Rationale: Inconsistent application leads to uneven finish. 50.What is the final layer in plastering called? A. Scratch coat B. Brown coat C. Finish coat D. Base coat Rationale: The finish coat provides final appearance and texture. 51.What is the main purpose of the finish coat? A. Structural support B. Insulation C. Aesthetic and smooth surface finish D. Waterproofing only Rationale: It provides the final decorative surface. 52.Which material improves fire resistance in plaster? A. Wood fibers
B. Above 120°F C. Moderate temperatures (40°F–90°F) D. Any temperature Rationale: Extreme temperatures affect curing and bonding. 58.What happens if plaster freezes during curing? A. Strength increases B. No effect C. Loss of bond and cracking D. Faster drying Rationale: Freezing disrupts hydration process. 59.What is the purpose of additives in plaster? A. Color only B. Reduce cost C. Improve performance (workability, strength, setting time) D. Weaken mix Rationale: Additives modify plaster properties. 60.What is key for plaster storage materials? A. Open air exposure B. Moist environment C. Dry, sealed storage D. Direct sunlight Rationale: Moisture ruins plaster materials before use. 61.What is the function of a scratch coat key? A. Decoration B. Insulation C. Mechanical bonding surface D. Waterproofing Rationale: Keys help layers grip together. 62.What is the effect of too much lime? A. Hard surface
B. Faster curing C. Soft and weak plaster D. No effect Rationale: Excess lime reduces strength. 63.What is the main purpose of sand in plaster? A. Color B. Binding C. Bulk and strength control D. Waterproofing Rationale: Sand provides structure and reduces shrinkage. 64.What causes plaster sagging? A. Too little water B. Too dry mix C. Excess water or thick application D. Cold weather Rationale: Heavy wet mix cannot hold shape. 65.What is the best method to repair cracks? A. Ignore them B. Paint over C. Clean, fill, and re-finish properly D. Add water Rationale: Proper repair prevents recurrence. 66.What is bonding agent used for? A. Decoration B. Cooling C. Improve adhesion between surfaces D. Reduce curing time Rationale: It strengthens interface bond. 67.What is the function of curing water spray? A. Wash surface
B. Brush C. Gauge rod or screed D. Saw Rationale: Screeds help control thickness. 73.What is the main cause of rust stains in plaster? A. Sand B. Water C. Metal lath corrosion D. Lime Rationale: Corroding metal lath produces stains. 74.What is the role of expansion joints? A. Decoration B. Reduce cost C. Allow movement without cracking D. Increase thickness Rationale: They absorb structural movement. 75.What is a plaster float used for? A. Cutting B. Mixing C. Smoothing surface D. Measuring Rationale: Floats level plaster surfaces. 76.What is the cause of blistering? A. Low water B. Proper curing C. Air trapped beneath surface D. Excess sand Rationale: Air pockets expand during drying. 77.What is the function of scratch coat grooves? A. Decoration
B. Water drainage C. Mechanical bonding improvement D. Insulation Rationale: Grooves help next coat adhere. 78.What is the best practice for mixing plaster? A. Random timing B. Overwatering C. Measured ratios and consistent blending D. Dry mixing only Rationale: Consistency ensures strength. 79.What is the purpose of plaster reinforcement mesh? A. Decoration B. Cooling C. Crack resistance and strength D. Drying speed Rationale: Mesh distributes stress. 80.What is the effect of high humidity during curing? A. Faster drying B. Weakening C. Slower, more controlled curing D. No effect Rationale: Humidity slows evaporation. 81.What is the function of a trowel? A. Cutting wood B. Mixing cement C. Applying and finishing plaster D. Measuring angles Rationale: Trowels spread and smooth plaster. 82.What is the main purpose of plaster base preparation? A. Decoration
B. Cracks C. Smooth, even, crack-free finish D. Hollow sound Rationale: Quality plaster is uniform and solid. 88.What is the function of bonding plaster additives? A. Speed drying B. Color only C. Improve adhesion and flexibility D. Reduce sand Rationale: Additives enhance performance. 89.What is the main cause of poor finish coat appearance? A. Proper curing B. Good tools C. Uneven application or improper troweling D. Clean surface Rationale: Technique affects finish quality. 90.What is the purpose of plaster leveling guides? A. Decoration B. Insulation C. Maintain uniform thickness D. Dry faster Rationale: Guides ensure consistency. 91.What is a key safety hazard in plastering? A. Noise B. Light exposure C. Falls from height D. Heat only Rationale: Working at height is dangerous. 92.What is the effect of too little water in plaster? A. Weak mix
B. Better flow C. Poor workability and weak bonding D. Faster setting only Rationale: Insufficient water prevents proper hydration. 93.What is the main purpose of scratch coat curing? A. Dry fast B. Color change C. Prevent shrinkage cracks D. Increase sand Rationale: Moisture retention prevents cracking. 94.What is used to check wall flatness? A. Hammer B. Brush C. Straightedge D. Drill Rationale: Straightedges detect uneven surfaces. 95.What is plaster bond failure usually caused by? A. Proper mixing B. Good curing C. Dirty or smooth substrate D. Low humidity Rationale: Contaminated surfaces prevent adhesion. 96.What is the purpose of a finish float? A. Cutting B. Measuring C. Creating final smooth texture D. Mixing Rationale: Floats refine surface texture. 97.What is the effect of rapid drying wind on plaster? A. Strength increase
