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INSTRUCTIONS AND GUIDES

The processes for mixing, applying, and curing Pozzolanic Hydraulic Lime (PHL) plasters is a different in performance-crucial ways from those of Portland-cement based stuccos and plasters. This catalog of published guides will help those new to PHL-type lime plasters and first-time installers get it right. The guides are available as cross-linked web pages for online reference as well as PDF downloads for printed reference, with some of the supplemental information available in PDF only. The Quick Reference Guide (accessed below) bundles key reference information pulled from various guides.

QUICK REFERENCE GUIDE +

COAT APPLICATION THICKNESSES (RECOMMENDED)
The SCRATCH COAT thickness depends on the substrate to which it is being applied (see substrate-specific guides), but typically one-quarter (1/4) to three-eights (3/8) of-an-inch in thickness.
Apply the LEVELING (BROWN) COAT at a thickness of three-eights (3/8) to one-half (1/2) of an inch; no more than 1/2-inch.
An LSB COARSE FINISH plaster coat goes on at one-eighth (1/8) to one-quarter (1/4) inches thick. Use when a deeper, rough-textured finish will be worked into the surface.
An LSB FINE FINISH plaster coat goes on at one-sixteenth (1/16) to one-eighth (1/8) inches thick. Use when a slightly-textured to smooth finish is desired.
An LSB INTERIOR FINISH plaster coat is typically applied in two thin layers, each one-sixteenth (1/16) inches thick, for a total thickness of one-eighth (1/8) inch.
BINDER:SAND RATIOS (RECOMMENDED)
RICH SCRATCH COAT [1 : 1] 1-part LSB Binder to 1-part Plaster Sand. EXAMPLE: 2 five-gallon buckets LSB Binder (one 50 lb. bag) : 2 five-gallon buckets of sand. Start with 3 gallons of water; add more water as necessary to bring up to proper working consistency.
STANDARD SCRATCH COAT [1 : 1.5–2]1-part LSB Binder to 1.5 (up to 2) parts Plaster Sand. EXAMPLE: 2 five-gallon buckets LSB Binder (one 50 lb. bag) : 3 or 4 five-gallon buckets of sand. Start with 4 gallons of water; add more as necessary to bring up to proper working consistency.
LEVELING (BROWN) COAT [1 : 2–2.5]1-part LSB Binder to 2 (up to 2.5) parts Plaster Sand. EXAMPLE: 2 five-gallon buckets LSB Binder (one 50 lb. bag) : 4 or 5 five-gallon buckets of sand. Start with 5 gallons of water; add more water as necessary to bring up to proper working consistency.
FINISH COAT LSB BINDER: 1-part LSB Binder to 1/2 (up to 1) part Fine Finish Sand. LSB FINISH: 1 bag (32 lbs.) of Limestrong Build FINISH (contains sand/aggregate) + 2.3 gallons of water.
WEIGHT-TO-VOLUME BASICS
• A single bag of LSB Binder, by volume, is approximately ten (10) gallons and weighs 50 lbs.
• A five-gallon (5G) bucket of plaster sand (not quite full) weighs 60–70 lbs. (depending on moisture content of sand).
• A five-gallon bucket (not quite full) of water weighs around 40 lbs.
EXAMPLE: Weight Ratio for Basic Scratch Coat: 50 lbs. (1 bag) Binder (two 5G buckets) + 250 lbs. damp plaster sand (four 5G buckets) + 4 gallons of water.
COVERAGE PER BAG
LSB BINDER. Coverage per 50 lb. bag of Binder will vary greatly depending on applied thickness and richness ratio (binder : sand) used.
LSB COARSE FINISH. Coverage per 32 lb. bag at a single-coat maximum application thickness of 1/4" is approximately 50 square feet.
LSB FINE FINISH. Coverage per 32 lb. bag at a single-coat maximum application thickness of 1/8" is approximately 80 to 100 square feet.
LSB INTERIOR FINISH. Coverage per 32 lb. bag at a two-coat maximum application thickness of 1/8" total is approximately 80 to 100 square feet.
COVERAGE CALCULATORS
MUD TESTS
THE RIGHT SAND: STRETCH TEST: One pre-purchase performance test for verifying you’re buying the right lime plaster sand is this stretch test. After mixing a test batch following the Limestrong plaster mixing instructions, pull a hawk-full of plaster mud across a table or mud-board with a plaster trowel. A great plaster will spread smoothly, with little effort, staying together—and that means the sand’s grade blend is right. If instead you get rips and tears, the sand has TOO FEW fines. If it’s too stiff and hard to spread (at recommended water amount), the sand has TOO MANY fines (sand or silts and clays), which tempts you to add more water to soften it up, which introduces other problems.
THE RIGHT SAND: STICKY 180 TEST: Another pre-purchase performance test to verify the plaster sand provides the right consistency and binding stickiness: scoop a load of prepared sample-batch plaster onto a small trowel, give it an abrupt, downward shake to set the plaster against the trowel, then quickly turn the little trowel upside down. If the plaster sticks to the trowel, you’re good to go. (Note: using a little margin trowel assures the mud sample is not too large and heavy.)
PROPERLY MIXED MUD TEST: Once you have determined you’re using the right plaster sand, use this test to verify you’ve got the mixer-sized mix times and component ingredients right. Take a sample of the newly-mixed mud and put it on a horizontally-held mason’s trowel. The mud should slump to about 2-inches high. If the mud is running off the trowel, it’s too wet; if it forms cracks, it’s too dry. If the mud stays stuck to the trowel when held horizontal and through up to 30-degrees of horizontal, but slides off when tipped at 45-degrees or more, the mix is right. If the mud does not release and slide off at 45-degrees, it probably doesn’t have as much water as it needs. If the mud slides off as soon as you begin tipping the trowel, it’s too wet.

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INSTRUCTIONS AND GUIDES

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