Parging is a finishing technique used in masonry construction to create a smooth, uniform surface on rough or imperfect walls. It involves applying a thin layer of cement-based plaster over concrete, stone, brick or other masonry.
Parging serves both functional and aesthetic purposes – protecting the underlying masonry while giving it an attractive finished appearance. Understanding what parging is, and its benefits, helps homeowners make informed decisions about maintaining and improving their property.
A Brief History of Parging
The origins of parging date back centuries, with early versions using lime plaster and other traditional materials. It was commonly used in English architecture in the 1600s and 1700s on brick and stone structures.
Parging grew in popularity in North America in the late 19th and early 20th centuries as concrete block and poured concrete foundations became standard. It provided a smooth, clean surface for these rough wall materials.
Over time, parging techniques evolved to use various cement, acrylic and chemical mixtures. However, the basic concept remains unchanged – applying a thin plaster coating to achieve a uniform surface. Examining the history provides context on what parging is and why it emerged as a useful building technique.
The Composition of Parging Plaster
There are two main types of parging plaster used today:
- Cement parging – Made from Portland cement blended with sand, lime and other additives. It provides high adhesion and durability.
- Acrylic parging – Uses acrylic polymer binders mixed with cement and aggregates. Offers increased flexibility and water resistance.
Cement parging is the more traditional option. Pre-mixed formulas are available containing polymers and fibers for improved performance. For small jobs, basic Type N mortar is commonly used.
Acrylic parging is a newer material gaining popularity. It starts with a base layer of acrylic-modified cement, then embed fiberglass mesh, applying the acrylic topcoat last. Acrylic parging costs more but has superior longevity and aesthetics.
Understanding the different plaster materials used helps clarify what parging is on a fundamental level. There are options available to suit specific project needs and budgets.
How Thick is Parging Plaster Applied?
A key trait of parging plaster is that it’s applied in thin layers, typically no more than 3/8 inch thick. Applying it too thick can lead to cracking and other problems.
The plaster is worked into the pores and cavities of the underlying masonry using a mason’s trowel. This scratch coat bonds it to the wall. After drying, a second smooth finish layer can be added if desired.
Proper parging technique involves using the thinnest workable coverage. This allows maximum adhesion and prevents the plaster drying too quickly before it bonds. Understanding parging depth helps clarify what parging is in practical application.
Why Use Parging Plaster?
There are several good reasons to apply parging:
- Aesthetics – Provides an attractive uniform finish over rough, non-decorative masonry.
- Weatherproofing – Seals pores and minor cracks against water intrusion.
- Insulation – Creates an air barrier reducing drafts for better energy efficiency.
- Damage repair – Covers cracks, spalls and deteriorated masonry surfaces.
- Versatility – Suitable for use on concrete, brick, stone and cement block foundations.
- Affordability – Less expensive compared to replacing existing masonry.
These benefits help explain the popularity of parging for building and home improvement projects. Understanding the ‘why’ behind parging helps gain full insight on what parging is and its advantages.
Where is Parging Used?
Parging plaster is used in the following areas:
- Foundations – Provides a clean finish on above-grade foundation walls. Seals minor settlement cracks common in concrete block foundations.
- Chimneys – Covers damaged brick or stonework on chimney faces and flues. Repairs pointing deterioration around chimney caps.
- Walls – Applied over unattractive or mismatching masonry materials to unify surfaces. Improves soundproofing in interior walls.
- Landscape walls – Provides a decorative finish for retaining walls, garden walls and other landscape masonry features.
- Pavements – Used to resurface damaged concrete walks, steps and driveways when replacement isn’t possible.
These examples help further illustrate what parging is through real-world applications. Knowing where parging plaster is useful aids in determining its suitability for specific projects.
Parging Process Step-by-Step
While professionals obtain the best results, DIY parging is possible in some cases. Here is an overview of the typical process:
- Surface prep – Clean area and remove any loose material or flaking parging. Soak wall thoroughly before plastering.
- Prime – Apply concrete bonding agent to improve adhesion.
- Base coat – Trowel on the first thin layer of parging plaster as a scratch coat.
- Reinforce (optional) – Embed fiberglass mesh if needed for structural enhancement.
- Finish coat – Apply a smooth decorative layer of plaster once base coat has cured.
- Cure – Mist plaster with water for several days as it cures to prevent cracking.
Understanding the step-by-step parging procedure provides insight on what parging is in a practical workflow. This helps set accurate expectations for the process.
Maintenance and Repair of Parging
Like any building material, parging requires periodic inspection and maintenance. Basic care includes:
- Watch for cracks forming – seal them quickly before water enters.
- Clean parging periodically with mild detergent and water.
- Check for areas becoming brittle, damaged or detached – repair promptly.
- Re-apply protective sealer coats as needed to refresh water resistance.
Minor damage can often be patched by a pro matching the original texture and color. Severely deteriorated parging may need complete replacement.
Knowing how to properly maintain parged surfaces ensures maximum longevity, and avoids the need for major repairs down the road. This helps provide a complete picture answering what parging is over the full building lifecycle.
Key Takeaways on What Parging Is
Parging is the application of thin plaster layers over masonry surfaces to create uniform, protected finishes. Key points include:
- It involves applying special cement-based or acrylic-based plasters.
- Serving both aesthetic and functional purposes.
- Used on foundations, chimneys, walls and other masonry.
- Requires proper technique to avoid durability issues.
- Needs periodic inspection and maintenance like any building material.
Fully grasping what parging is allows for wise decisions about how to utilize it effectively in construction and renovation projects.
Frequently Asked Questions About Parging
Below are answers to some commonly asked questions to further clarify what parging is and how it works:
What is the benefit of parging over just painting masonry?
Unlike paint, parging plaster seals pores, minor cracks and imperfections that could allow moisture intrusion. It adds an extra weather barrier and helps stabilize deteriorating masonry through its bonding properties.
Can parging be applied over painted brick or stucco?
It is not recommended. Parging requires a mechanical bond with the masonry underneath, which paint or stucco can compromise. Complete removal is ideal but pros may be able to sand or roughen painted surfaces if needed before parging.
How long does parging last?
With proper installation and maintenance, parging can last 20-30 years or longer. Acrylic-based parging tends to have a longer service life than traditional cement parging. Outdoor exposure, weathering, soil contact and other factors affect durability.
Is parging waterproof?
It is considered water-resistant but not fully waterproof. Parging helps protect the masonry foundation from moisture but does not provide a complete barrier on its own. It is normally used in conjunction with other waterproofing elements as part of a comprehensive moisture control system.
Can I install parging myself or do I need to hire a pro?
It is possible for DIYers to parge small areas successfully. However, hiring an experienced mason is highly recommended for important structural projects, large jobs or anything beyond basic patch repairs. A pro can ensure proper preparation, materials, technique and curing essential for long-lasting results.
In summary, parging is the process of applying specialized thin plaster layers over masonry surfaces. It serves to beautify, strengthen and protect while providing versatility for repairing or enhancing concrete, stone, brick and other masonry building materials.
Understanding what parging is, along with its history, composition, benefits and applications allows for informed usage in construction and home improvement projects. Taking a comprehensive view also ensures proper maintenance and repair over its lifetime.
While a simple concept, proper parging technique is nuanced – leading many homeowners to seek out professional plastering contractors rather than DIY. When executed successfully, it provides an affordable, long-lasting solution for both decorative and practical masonry improvement.