Gypsum Plaster

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Gypsum Plaster

What is Gypsum Plaster?

A smooth, hard interior wall and ceiling finish material made from gypsum powder mixed with water and additives, applied in multiple coats over lath or gypsum board to create durable, fire-resistant surfaces.

Description

Gypsum plaster is a smooth, hard interior wall and ceiling finish material made from gypsum powder mixed with water and additives, applied in multiple coats over lath or gypsum board substrates to create durable, fire-resistant surfaces with superior aesthetic and performance qualities. This traditional plastering material, also known as plaster of Paris when in its pure form, provides excellent workability during application and hardens to create seamless, monolithic surfaces that can be finished to various textures and painted or decorated as desired. Gypsum plaster has been used for centuries in construction and remains popular for high-quality interior finishes, restoration work, and applications requiring superior fire resistance and acoustic properties.

The primary purposes of gypsum plaster include creating smooth, seamless interior wall and ceiling surfaces, providing superior fire resistance compared to other finish materials, offering excellent acoustic properties for sound control, enabling decorative finishes and architectural details, providing durability and longevity for interior surfaces, allowing for repair and restoration of existing plaster surfaces, and creating high-quality finishes for premium construction and historic preservation projects.

Composition and properties of gypsum plaster include calcined gypsum (calcium sulfate hemihydrate) as the primary binding agent, sand or other aggregates for body and strength, lime putty or hydrated lime for workability and plasticity, fiber reinforcement such as goat hair or synthetic fibers for crack resistance, retarders to control setting time, and various additives to enhance specific properties such as hardness, workability, or water resistance.

FAQs

  • What is gypsum plaster?

    Gypsum plaster is a smooth, hard interior finish material made from gypsum powder mixed with water and additives, applied in multiple coats to create seamless, fire-resistant wall and ceiling surfaces.

  • What are the main types of gypsum plaster?

    Main types include neat plaster for smooth finishes, sanded plaster with aggregate for base coats, fibered plaster with reinforcement, and veneer plaster for thin-coat applications.

  • How is gypsum plaster applied?

    Gypsum plaster is typically applied in multiple coats, including a scratch coat for bonding, a brown coat for leveling, and a finish coat for final texture, over prepared lath or gypsum board substrates.

  • What are the advantages of gypsum plaster?

    Advantages include excellent fire resistance, strong acoustic performance, seamless appearance, decorative versatility, durability, repairability, and compatibility with various finishes.

  • Where should gypsum plaster not be used?

    Gypsum plaster should not be used in high-moisture areas such as bathrooms or exterior applications, as prolonged exposure to water and humidity can cause damage.

  • How long does gypsum plaster take to cure?

    Gypsum plaster sets quickly, typically within 30 to 60 minutes, but requires several days to fully cure and dry, with each coat needing adequate drying time before the next application.

  • Can gypsum plaster be repaired?

    Yes, gypsum plaster can be repaired by removing damaged areas, applying new plaster in matching coats, and blending the repair seamlessly with existing surfaces when done by skilled craftsmen.

Fun Fact

Fun Fact: Gypsum plaster has been used for over 4,000 years – ancient Egyptians used it to plaster the interior of the Great Pyramid of Giza around 2580 BC! The term “plaster of Paris” comes from large gypsum deposits near Paris, France, that were mined extensively in the 18th century. Interestingly, the same chemical reaction that makes gypsum plaster fire-resistant (releasing water vapor when heated) also makes it self-limiting – it won’t burn and actually helps extinguish fires!

CSI Code

09 24 00

NAHB Code

920