Table of Contents

What Is Plastering?

Plastering is the craft of applying plaster — a mixture of calcium-based compounds, sand, and water — to walls, ceilings, and other surfaces to create smooth, hard, durable finishes. It’s one of the oldest building trades, practiced for at least 9,000 years (the walls of Ain Ghazal in Jordan, dated to approximately 7000 BCE, have lime plaster surfaces). Before drywall became dominant in the mid-20th century, virtually every interior wall in the Western world was plastered by hand. The craft hasn’t disappeared — it’s just become more specialized.

The Materials

Gypsum plaster is the most common type in modern construction. Gypsum (calcium sulfate dihydrate) is heated to drive off water, creating plaster of Paris. When mixed with water again, it recrystallizes and hardens — a chemical reaction, not just drying. Gypsum plaster sets quickly (20-90 minutes depending on the formula), is easy to work, and produces a smooth white surface. It’s not waterproof, so it’s limited to interior use.

Lime plaster is the traditional material, used for millennia before gypsum became standard. Made from limestone that’s been burned (calcined) to produce quicklime, then slaked with water to create lime putty, it’s mixed with sand to make plaster. Lime plaster sets slowly — it cures through carbonation, absorbing carbon dioxide from the air and gradually reverting to calcium carbonate (essentially turning back into limestone). This process takes weeks to months.

Lime plaster has properties that make it superior to gypsum in certain applications: it’s flexible (it moves slightly with the building without cracking), breathable (it allows moisture to pass through, preventing trapped dampness), and self-healing (small cracks can re-seal as dissolved lime migrates with moisture and re-carbonates). Historic preservation almost always uses lime plaster.

Cement plaster (stucco, when used on exteriors) combines Portland cement with sand and water. It’s stronger and more water-resistant than either gypsum or lime plaster, making it suitable for exterior surfaces. It sets hard and brittle — less forgiving of building movement than lime plaster.

Clay plaster uses natural clay as the binder, mixed with sand and often straw or other fibers. It’s the oldest plaster type and is experiencing a revival in green building. Clay plaster is non-toxic, regulates humidity naturally, and has a warm, earthy aesthetic.

The Process

Traditional plastering applies material in multiple coats, each serving a specific purpose:

Scratch coat (first coat). The base layer, applied directly to the lath — historically thin strips of wood (wooden lath) nailed to wall studs, now typically metal or expanded metal mesh. The plaster is pushed through the gaps in the lath and curls behind it (forming “keys”), creating a mechanical bond that holds the plaster to the wall. The surface is scratched with a comb or rake before it hardens to provide grip for the next coat. Thickness: roughly 3/8 inch.

Brown coat (second coat). Applied over the scratched surface once the first coat has set. This coat builds up the thickness and is leveled (screeded) to create a flat, even surface. The brown coat is left with a slightly rough texture to bond with the finish coat. Thickness: roughly 3/8 inch.

Finish coat (skim coat). The final thin layer — typically 1/16 to 1/8 inch — that provides the smooth surface you actually see and touch. The finish coat is applied and then polished (burnished) with a steel trowel to compress the surface and create a hard, smooth plane. The timing of this finishing step is critical — too early and the plaster is too wet to polish, too late and it’s too hard to work.

The Skills

Plastering is physically demanding and technically precise. The core skills include:

Trowel work. Applying plaster with a steel trowel (a flat, rectangular metal blade with a handle) in smooth, consistent strokes. The angle, pressure, and speed of the trowel determine how the plaster spreads and compresses. Getting a truly flat, smooth surface requires years of practice.

Timing. Plaster sets on its own schedule. The plasterer must mix the right amount (what can be applied before it sets), apply it efficiently, and know exactly when the plaster is ready for each stage of finishing. Work too slowly and the plaster hardens before you’ve finished. Rush it and the surface won’t polish properly.

Surface reading. Experienced plasterers can see and feel imperfections that most people would miss — slight hollows, ridges, trowel marks. Correcting these requires subtle manipulation during the final finishing passes.

Mixing. Getting the right consistency — not too wet (slides off the trowel), not too dry (won’t spread smoothly). Different coats need different consistencies. Plaster consistency affects working time, adhesion, and final surface quality.

Plastering vs. Drywall

Drywall (gypsum board) largely replaced wet plastering in North American new construction starting in the 1940s-1960s. The reasons were economic: drywall is manufactured in a factory and installed by screwing sheets to studs. A crew can drywall a house in a day. Traditional plastering takes a week or more, requiring multiple coats with drying time between each.

But plaster has real advantages:

• Harder surface — plaster walls resist dents and damage that would puncture drywall
• Better sound insulation — plaster’s greater density and mass reduce sound transmission
• Smoother finish — a skilled plaster job is smoother than any drywall finish
• Moisture regulation — lime and clay plasters breathe, buffering indoor humidity
• Longevity — properly maintained plaster walls last centuries (many pre-1900 buildings still have original plaster in good condition)

The tradeoff is cost. Wet plastering costs 3-5 times more than drywall, almost entirely due to labor. In new construction where budget matters, drywall wins. In historic restoration, high-end custom homes, and buildings where quality justifies cost, plaster remains the superior finish.

Plastering is a trade where the difference between competent and exceptional shows in the result. A well-plastered wall has a solidity, smoothness, and character that no manufactured board can quite replicate. It’s the difference between a printed poster and an oil painting — both cover the wall, but one has a quality the other doesn’t.

Frequently Asked Questions

What is the difference between plaster and drywall?

Drywall (also called Sheetrock or plasterboard) is a pre-manufactured panel of gypsum sandwiched between paper, screwed to wall studs, with joints taped and coated with compound. Traditional plaster is applied wet directly over lath (wood strips or metal mesh) in multiple coats, each one drying before the next. Drywall is faster and cheaper to install. Plaster is denser, harder, more soundproof, and more durable, but costs 3-5 times more in labor.

How long does plaster take to dry?

Drying time depends on the plaster type, coat thickness, temperature, and humidity. Gypsum plaster typically sets (hardens chemically) within 20-90 minutes, depending on the mix. But it needs additional time to dry fully — usually 1-3 days per coat. Lime plaster takes much longer — weeks to months to fully carbonate and cure. Applying paint or wallpaper over plaster that hasn't dried completely traps moisture and causes problems.

Is plastering a dying trade?

In new construction, traditional wet plastering has been largely replaced by drywall in North America since the 1950s-1960s. However, plastering remains essential for historic restoration, high-end custom homes, decorative work, and renovation of older buildings. In the UK and much of Europe, wet plastering is still the standard finish for interior walls. Skilled plasterers are in demand, and apprenticeship programs continue to train new tradespeople.

Further Reading

• National Plastering Industry's JATC
• Britannica - Plaster
• National Trust - Traditional Lime Plaster