On this page
On concrete block, the question mostly doesn't come up: stucco bonds straight to block in two coats, with no lath. The one-coat versus three-coat choice is about wood and steel frame walls.
The Short Answer
| Three-coat stucco | One-coat stucco | |
|---|---|---|
| Coats | Scratch, brown and finish | One base coat, then a finish coat |
| Plaster thickness | About 7/8 inch over lath | About 3/8 inch base coat, plus the finish |
| The mix | Portland cement, sand, lime and water, mixed on site | A maker's premixed blend with reinforcing fibers |
| What it follows | ASTM C926 and the Florida Building Code, Section R703.7 | The maker's evaluation report |
| Goes over | Two layers of water-resistive barrier and metal lath | Lath over sheathing or foam insulation board, per the report |
| Time | About two weeks or more from lath to finish | Faster: one base coat to cure instead of two |
How Three-Coat Stucco Is Built
Three-coat stucco is the original method and still the code's standard for portland cement plaster over lath:
- Scratch coat. About 3/8 inch, pushed into the metal lath and raked with horizontal grooves so the next coat grips. It's kept moist for at least 48 hours.
- Brown coat. About 3/8 inch more, straightened flat and true. It goes on at least 48 hours after the scratch coat and is kept moist too.
- Finish coat. About 1/8 inch, carrying the color and texture, from smooth to sand to heavier troweled looks.
Together they add up to about 7/8 inch of plaster, the thickness ASTM C926 sets for three-coat work over metal lath. Under the plaster go two layers of water-resistive barrier and the lath, with a weep screed at the bottom of the wall. Our stucco installation guide walks through each step under the 2023 Florida Building Code.
How One-Coat Stucco Is Built
"One-coat" is a little misleading: it's one base coat plus a finish coat. The base coat replaces both the scratch and brown coats with a single layer, about 3/8 inch thick, of a premixed blend that carries its own reinforcing fibers.
QUIKRETE's One Coat Fiberglass Reinforced Stucco is a typical example. Its maker describes it as a proprietary mix of portland cement, lime, sand and alkali-resistant glass fibers, applied over wire fabric or metal lath on foam insulation board, fiberboard, plywood, OSB or gypsum sheathing, at 3/8 inch.
Because one-coat products are proprietary, each one is installed under its own evaluation report rather than the general three-coat method. The report spells out the approved lath, sheathing, barrier, thickness and finish. StoPowerwall One Coat, for example, has an ICC-ES report (ESR-2323) that describes it as a cementitious wall covering "installed on wood or steel framed exterior walls." One-coat systems are often paired with a layer of foam insulation board under the lath.
Which Is Better?
Neither one wins everywhere. They suit different jobs:
- Three-coat is thicker and follows the general code method, so any qualified plasterer can build and repair it with standard materials. It takes longer because there's one more coat to cure.
- One-coat goes up faster, works well over foam insulation board, and is common on new frame construction. It only performs as tested when the job follows the product's evaluation report exactly, from the lath to the thickness.
- On concrete block, most Florida homes, neither applies: stucco goes on in two coats straight on the block.
Questions to Ask About the System on Your Walls
Whether you're building new or repairing, it helps to know which system is on the wall:
- Is the wall block or frame?
- If it's frame, is the stucco three-coat or one-coat?
- For one-coat, which product, and which evaluation report does the job follow?
- What's under the stucco: which barrier, which lath, and is there foam board?
- Who pulls the permit, and when is the lath inspection?
A repair matches what's already on the wall, so knowing the system helps your contractor plan it and price it. Your local Stucco HQ contractor sees the walls in person and puts a free quote in writing. See how a stucco installation job runs.
Frequently asked questions
How many coats of stucco do you need?
On a wood frame wall, traditional stucco takes three coats: scratch, brown and finish. A one-coat system takes one base coat plus a finish coat. On concrete block, stucco goes on in two coats, bonded straight to the block.
How thick is three-coat stucco?
About 7/8 inch over metal lath: roughly 3/8 inch scratch coat, 3/8 inch brown coat and 1/8 inch finish coat. That's the thickness ASTM C926 sets for three-coat plaster over lath.
What is the difference between the scratch coat and the brown coat?
The scratch coat is the first coat, pushed into the lath and raked with grooves so the next coat grips. The brown coat goes over it and is straightened flat and true, ready for the finish coat.
Is one-coat stucco really one coat?
Not quite. It's one base coat, about 3/8 inch, in place of the scratch and brown coats, plus a finish coat on top.
Is one-coat stucco cheaper than three-coat?
It usually takes less labor and time, since there's one base coat to apply and cure instead of two. The total price depends on the whole wall: the product, the foam board if there is one, the lath, the finish and the size of the job.
Can stucco on concrete block be one-coat?
The one-coat versus three-coat choice is about framed walls. On concrete block, stucco bonds straight to the block in two coats, a base coat and a finish coat, with no lath.
Sources and data used on this page
The figures and facts on this page come from public records and official sources. Links open in a new tab.
Florida code and standards
- 2023 Florida Building Code, Residential, 8th Edition International Code Council Three-coat stucco over lath: the coats, the barrier, the weep screed and the cure times.
- C926-26 Standard Specification for Application of Portland Cement-Based Plaster ASTM International The 7/8 inch of three-coat plaster over metal lath.
Product makers and evaluation reports
- One Coat Fiberglass Reinforced Stucco QUIKRETE What a one-coat product is made of, what it goes over, and its 3/8 inch thickness.
- ESR-2323: StoPowerwall One Coat Stucco System ICC Evaluation Service An example of the evaluation report a one-coat system is installed under.
Last reviewed:
Stucco HQ is not affiliated with the International Code Council, ICC Evaluation Service, ASTM International, QUIKRETE or Sto. Checked against the 2023 Florida Building Code (8th Edition) and the makers' documents on November 12, 2026. This page is general information; the code, your permit drawings and the product's evaluation report have the final say.