Glossary of Lath, Plaster, EIFS, and Adhered Veneer Terminology

Introduction

Understanding the terminology used in lath and plaster systems is essential for clarity and precision in work or learning. This glossary provides detailed explanations of terms commonly used in the industry. Where applicable, ASTM standards are referenced for consistency.

Glossary

A

• Accessories: Trim components in stucco systems, such as control joints, expansion joints, corner beads, drip screeds, and casing beads.
• EIFS Accessories (ASTM C2110): Preformed metal, fiberglass, or plastic members for forming corners, edges, control joints, or decorative effects.
• Adhesion: The state where two surfaces are held together by physical or chemical forces.
• Admixture: Material added to a mix (other than water, aggregate, or basic cementitious material) to enhance performance or workability.
• Aggregate: Granular material such as sand or synthetic particles that form a matrix when bound with cement plaster.
• Aesthetics: Judgment regarding the visual appearance of an item.
• Aesthetic Reveal: A decorative groove cut into insulation board for decorative or functional purposes.
• Air Entrainment: Additive in the basecoat mix to reduce water content and improve performance.

B

• Basecoat: The total stucco coats applied prior to the finish coat. Includes the scratch and brown coats in traditional applications or the single coat in one-coat stucco systems.
• Batching: Measuring and introducing ingredients into a mixer for a batch of cement plaster.
• Bedding Coat: A plaster coat that receives aggregate or decorative material before setting.
• Bond: The adhesion of stucco to surfaces, including the substrate and between stucco coats.
• Bonding Agent: A compound applied to a substrate to enhance adhesion between layers.
• Brown Coat: The second coat in multi-coat work, applied over the scratch coat and beneath the finish coat.
• Building Code: Regulations governing building construction adopted by authorities.
• Bullnose: Trim accessory creating a rounded exterior corner or rounded corners formed during installation.

C

• Calcium Aluminate Cement: Cement added to Portland cement to accelerate setting.
• Casing Bead: Termination trim accessory in stucco systems, often used as a plaster stop.
• Casing Weep Bead: A casing bead with perforations for drainage.
• Caulking: Resilient material used to fill cracks or joints between dissimilar materials.
• Cement Hydraulic: Cement that sets and hardens by chemical interaction with water, including Portland cement.
• Channel Reveals: Decorative trim accessories creating delineation lines and shadow effects.
• Checking: Shallow cracks at closely spaced intervals, also known as craze cracks.
• Chemical Bond: Adhesion between materials due to chemical reactions.
• Cold Joint: Junction of fresh stucco adjacent to set plaster.
• Control Joint: Single-piece trim accessory for regulating cracking.

D

• Dash-Bond Coat: Thick mix of Portland cement and sand applied to create a mechanical bond for subsequent coats.
• Deflection: Displacement of the stucco system or building structure from its original position.
• Delamination: Separation of bonded layers.
• Density: Weight per unit volume of a material.
• Direct Applied: Application of stucco or EIFS components directly to a substrate without lath.
• Double Back Method: Application of a second stucco coat over the first immediately after it gains sufficient rigidity.
• Drainage Plane: Surface between the back of stucco cladding and the water-resistive barrier.
• Drip Screed: Device directing water flow on walls.

E

• Efflorescence: White deposits formed from water-soluble compounds emerging from substrates.
• EIFS (Exterior Insulation and Finish System): Non-structural, non-load-bearing cladding system consisting of an insulation board, reinforced basecoat, and finish coat.
• Expansion Joint: Multi-part trim accessory that divides the system to manage cracks from expansion or contraction.

F

• Fibers: Natural or synthetic strands added to stucco mixes to enhance cohesiveness and reduce cracks.
• Finish Coat: Final wet-state material providing color and texture.
• Flashing: Thin material preventing water entry and directing water flow.

G

• Gauge: Thickness of sheet metal or wire, measured in mils.
• Gradation: Size distribution of aggregate particles.
• Ground: Defined thickness or depth for a part of the stucco system.

H

• Hairline Cracks: Fine cracks just visible to the naked eye.
• Hydration: Chemical reaction between cement and water creating a hard stucco membrane.

L

• Lamina: Composite of the basecoat, reinforcement, and finish coat.
• Lath: Base reinforcement for plaster, secured to the substrate and providing a mechanical key for stucco.

S

• Scratch Coat: First cement plaster coat applied with pressure to create a mechanical bond.
• Sealant: Flexible material sealing joints and penetrations to prevent moisture and air intrusion.
• Stucco: Portland cement-based plaster for exterior surfaces.
• Stucco Finish Coat: A cementitious finish coat, factory mix or field mix.
• Stucco Systems: The systematic design and arrangement of various stucco-related components.
• Substrate: The surface to which the EIFS is applied or the stucco system is attached (either directly or indirectly). 
• Suction:The absorptive capacity of a substrate or stucco surface.
• Surface Sealer: A material used to enhance weather resistance and/or the appearance of the finished surface.

T

• Temper:To mix or restore unset plaster to a workable consistency. 
• Thermal Insulation Board: An uninterrupted system component of a specific type and density that functions to reduce heat flow through the wall and serves as the surface to receive the lamina. 
• Three-Coat Work:
  A stucco system with three different applications:

1. Scratch Coat: The first coat of cement plaster.
2. Brown Coat: The second coat applied over the scratch coat.
3. Finish Coat: The decorative top layer.

• Traditional Stucco: Types of stucco systems without rainscreen or continuous insulation design. 
• Trim Accessories: Mechanically attached components of the stucco system installed prior to plastering, such as control joints, corner beads, screeds, casing beads, etc. 
• Trim Accessory Joint (Control/Expansion Joint): A designated separation device in a stucco system allowing for movement caused by expansion or contraction. These joints are constructed using manufactured devices for this purpose. 
• Trowel: A flat, broad-blade hand tool used to apply, spread, shape, and finish surface materials.  
• Two-Coat Stucco System:A system where a cement plaster base coat is applied directly to a substrate (e.g., concrete or CMU) without lath, followed by a finish coat.

U

• U-Value: The coefficient of heat transmission or thermal transmittance. A U-Value measures the rate of heat transfer through an assembly, with lower values indicating better insulation performance.

V

• Vapor:The gaseous state of water (liquid) suspended in air. Vapor permeability is commonly tested using ASTM E96, expressed in perms.
• Vapor Barrier (Impermeable):A product designed to prevent vapor from penetrating or intruding into a space, typically rated at 1.0 perm or less.
• Vapor Permeable: The property of a material that allows moisture to pass through as a gas (vapor). Higher perm ratings indicate greater permeability.

W

• Wall Assembly: The combination of total wall components and/or systems.
• Water-Resistant Barrier (WRB):A material placed behind an exterior wall covering to resist liquid water that has penetrated the exterior from further entering the wall assembly.
• Weatherboard Fashion: The method of installing water-resistant barrier systems and/or flashing components so that moisture cannot come into contact with the building structure.
• Workability: The property of freshly mixed stucco determining its ease of mixing, placement, and finishing.

This glossary aims to provide a foundational understanding of terms integral to the lath, plaster, EIFS, and adhered veneer industries. For additional details, consult ASTM standards (e.g., E2110, C926, C1063).