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Lime Plaster

Calcium-hydroxide finish dating to Ancient Rome — vapor-open, alkaline, and naturally mold-suppressing.

Lime Plaster — a natural material we specify on every Earth Bound Homes project

Toxicity Screening — All Clear

This material screens clear across all seven independent toxicology authorities we use on every project.

LBC Red List

Not Listed

Prop 65

Not Listed

IARC

Not Listed

NTP RoC

Not Listed

GSPI

Not Listed

REACH SVHC

Not Listed

TSCA

Not Listed

Material Type

Mineral Wall & Ceiling Finish

Material Description

Lime plaster is one of the oldest wall finishes humans have used — Roman concrete and most pre-industrial interior walls were lime-based. Modern lime plaster is the same chemistry: calcium hydroxide (slaked lime) blended with sand and water, applied wet, and cured by absorbing atmospheric CO₂ back into calcium carbonate. The cured surface is high-pH (alkaline), which suppresses mold and bacterial growth without any added biocide. Lime plaster is vapor-open, meaning it lets the wall assembly breathe rather than trapping moisture behind gypsum drywall. EBH uses lime plaster in wet rooms, around wood-burning appliances, and where vapor-open assemblies are critical.

Composition & Origin

Ca(OH)₂ + sand + water → Ca(OH)₂ → absorbs atmospheric CO₂ → CaCO₃ (calcium carbonate) over weeks

Health Profile — All Endpoints Clear

Severity scored 0–10 against the same 10 hazard endpoints we use for the chemical families on the avoid list. Every score is 1–2 — essentially no signal across every endpoint.

Cancer

1/10

Endocrine

1/10

Reproductive

1/10

Developmental

1/10

Neurological

1/10

Respiratory

2/10

Cardiovascular

1/10

Liver/Kidney

1/10

Skin

2/10

Immune

1/10

Common Forms & Brands

American Clay Loma (with lime additive)
Limewash Co. lime plaster
Saint-Astier natural hydraulic lime
Common framing: lime putty, hydrated lime, hydraulic lime, tadelakt

Why We Use It

Alkaline pH naturally suppresses mold and bacteria
Vapor-open — allows wall assembly to dry
Absorbs CO₂ during cure — modest carbon sink
Self-healing — hairline cracks close as lime continues to recarbonate
Heat- and fire-resistant once cured

Where It Performs Best

Interior wall and ceiling finish
Bathroom wet-room walls (tadelakt finish)
Fireplace surrounds and masonry stove coverings
Vapor-open exterior renders

Building Applications for Lime Plaster

Listed alphabetically. Where in a home this material earns its keep.

Bathroom Wet-Room Walls (Tadelakt)
Decorative Interior Wall Finishes
Exterior Lime Render Coatings
Fireplace & Masonry Stove Surrounds
Interior Ceiling Finish

Specifying a project? Drop the manufacturer's SDS into our SDS Toxic Chemical Screener to verify any specific product you're considering screens clear on all seven databases.