Sampling and Characterizing Plaster Roger G. Morse AIA Dyanki, Inc.

Sampling and Characterizing Plaster A New System for Sampling and Characterizing Plaster in Three Dimensions

Homogeneous areas based on surface characteristics One type of plaster can have different surface characteristics Frequently results in large numbers of samples Typical Survey Looks at Plaster in Two Dimensions

Example of Homogeneous Plasters in Two Dimensions Smooth wall plaster Lumpy wall plaster Wainscot plaster Crown molding Molded plaster Sandy wall plaster Spattered plaster Knobby plaster Smooth ceiling Lumpy ceiling Applied decorations Sandy ceilings Highly painted ceilings Dashed ceilings High relief molded ceilings

Same Plasters in Three Dimensions Smooth white finish plaster Sandy white finish plaster Gray-beige base plaster

Plaster Classification

Initial Inspection Make an initial determination of likely homogeneous plaster types Collect a sufficient number of each type to meet AHERA requirements for surface treatments –1,000 SF – 3 samples –1,000 to 5,000 SF – 5 samples –Over 5,000 SF – 7 samples

Sample Collection Core drill connected to HEPA vacuum Clean dust from surface of cores in sealed cabinet with HEPA local exhaust

Plaster Core

Evaluate Plaster Cores Evaluate with stereo microscope Assign plaster type to each layer Verify that number of samples meets AHERA requirements

Gross Characteristics of Each Layer Layer – (top, middle, bottom) Function – (finish, base, scratch) Gross Color – Munsell Color System Thickness

Components of Each Layer Cement Aggregate Fiber

Cement - Type Gypsum Lime Gypsum/Lime Portland Cement Clear Adhesive

Cement Color White Off White Gray Exact colors from Munsell Color System

Aggregate - Type Sharp masons sand Perlite Vermiculite Mica Washed sand None

Aggregate Color Colorless Tan Brown Black Red Brown Exact color definition with Munsell Color System

Fiber - Type Hair – cattle or horse Wood fiber Jute Fiberglass Cellulose Suspected of being asbestos

Engineering Properties Plaster strength Bond between layers Useful for engineering design purposes

Determine Plaster Type Atlas of plasters Physical standards

Analyze Samples PLM Gravimetric Reduction Point Count (1000 points – Chatfield Method) Report concentrations of plaster components Report lime to gypsum ratio Determine if analysis verifies plaster type determination

Plaster Types Job mixed plasters Modern plasters Acoustical plasters Skim coats Plaster substrates Coatings

Job Mixed Plasters Colored sand plaster White smooth plaster White sand plaster Bond plaster Portland cement plaster (Stucco) Mortar and concrete

Modern Plasters Perlite aggregate Synthetic fiber reinforcing Gray granular gypsum cement Vermiculite aggregate

Acoustical Plasters Manufactured products Open porous texture Usually friable Each must be considered separately Frequently contain asbestos

Skim Coats Drywall taping compound Clear adhesive Fine aggregate (limestone, talc, marble) May be between layers of paint May not be able to find sufficient samples to meet AHERA requirements Evaluate separately for each facility

Plaster Substrates Gypsum lath Gypsum block Gypsum panels (drywall systems)

Coatings Textured coatings Heavy hard cementitous coatings (Thorocoat) May contain tremolite

Roger G. Morse AIA Dyanki, Inc. 504 Snake Hill Road Poestenkill, NY 12140