What Is Parging?
Parging is a thin layer of cement we trowel over exposed foundation walls. It hides rough block, seals tiny pores, and takes the daily scuffs from shovels, rain splash, and lawn work so the wall underneath stays safe.
Picture it as a protective skin. It does not fix major cracks or stop leaks on its own. It works alongside good grading, drains, and any dampproofing or waterproofing you already have in place.
Ontario Building Code (OBC 9.15.6) says block walls that sit below grade must get at least a 6 mm (¼ inch) coat before dampproofing. Inspectors look for smooth, even coverage that bonds tight to the wall—not a thick blob in one spot.
Need a simplified definition you can share with clients or teammates? Visit the What Is Parging? quick guide.
Parging vs Dampproofing vs Waterproofing
These three words get mixed up, but they do different jobs. Parging smooths and protects the surface. Dampproofing keeps soil moisture from soaking in. Waterproofing stops liquid water under pressure and usually needs membranes plus drains. Use them together so each layer backs up the others.
On concrete block walls, parging is the base coat that evens out joints before you brush on dampproofing or waterproofing. On poured concrete, we focus on cleaning the wall, filling tie holes, and sealing cracks before any coatings. Always follow the product sheet that comes with your materials.
Codes, Standards, and Local Requirements
Local rules follow the National Building Code (NBC 9.15.6) and the Ontario Building Code. Block walls that touch soil must be parged at least 6 mm thick before you add dampproofing. Smooth poured concrete can skip parging if every crack, tie hole, and honeycomb area is patched first. Older brick homes need breathable mixes so moisture can escape instead of bubbling the finish.
Inspectors often ask to see the data sheet for your bonding agent, mesh, and waterproofing membrane. Keep those PDFs handy so the permit visit is quick.
Materials and Systems
Most parging mixes start with cement, lime, sand, and water. Modern “polymer-modified” bags add glue-like latex so thin coats grab tight. We add mesh at joints or where one material meets another so the finish can flex without cracking.
Foam walls such as ICF need their own kits that include insulation-friendly mesh and impact-resistant coatings. Dense painted walls often call for a bonding primer so the new coat sticks.
Ontario crews now mix in acrylics, microfibers, or water-repellent additives to handle salt spray and 60+ freeze/thaw swings each winter. Check the bag limits so the finish can still breathe.
Debating which system suits brick, block, or ICF? Read our Concrete vs Brick Parging comparison for wall-specific pros and cons.
Types of Parging Systems
Three main parging systems dominate the Canadian market, each with distinct material properties, application methods, and performance characteristics. Understanding these types helps ensure the right system for your foundation and climate exposure.
What It Is
EIFS combines foam insulation board with a synthetic stucco finish. Applied over ICF (insulated concrete form) foundations or foam-core basement walls, EIFS adds insulation while creating a finished exterior.
Material Composition
- Rigid foam board (EPS or polyiso) at 1–2 inches thick
- Fiberglass mesh pressed into a cement-and-polymer basecoat
- A thin acrylic or polyurethane finish coat
- Color-safe acrylic resins to fight UV fading
Application Method
- Foam boards mechanically fastened to the wall
- Basecoat applied over mesh (typically 3/16")
- Topcoat applied for color and UV protection (typically 1/16"–1/8")
- Careful joint and transition work to prevent water infiltration
Durability in Ontario
- Expected lifespan: 15–25 years with proper maintenance
- Freeze-thaw performance: Excellent if installed per spec (foam absorbs movement)
- Weaknesses: Vulnerable at joints; poor if water gets behind foam
- Salt resistance: Good; acrylic topcoat resists de-icing salts
Best Use Cases
ICF foundations, foam-core basements, new construction where insulation is desired, above-grade walls where thermal performance matters.
Cost Considerations
Cost varies significantly based on foam thickness, wall condition, labor availability, and local market conditions. Request quotes from certified installers for accurate pricing.
What It Is
The classic mortar-based parging applied directly to masonry or concrete. Uses Portland cement, lime, and sand—the traditional approach for concrete block (CMU) foundations.
Material Composition
- Portland cement for strength
- Hydrated lime that makes the mix creamy and breathable
- Fine sand as the bulk of the mix
- Water plus, if needed, a small dose of bonding agent or air-entraining additive
Application Method
- Apply a thin scratch coat, score it, and let it set
- Follow with a smooth finish coat a few days later
- Choose a trowel or broom texture to match the rest of the wall
- Mist the wall for several days so the mortar cures slowly
Durability in Ontario
- Expected lifespan: 10–20 years (longer if properly maintained)
- Freeze-thaw performance: Excellent if air-entrained; poor if not (cracks in first freeze)
- Salt resistance: Good; permeable (allows moisture escape)
- Weaknesses: Can crack if applied too thick, dried too fast, or if the wall shifts
Best Use Cases
Concrete block (CMU) foundations, existing masonry repair, restoration projects, when vapor permeability is required (heritage masonry).
Cost Considerations
Cost depends on surface area, prep requirements, substrate condition, and regional labor rates. Get multiple quotes to compare options.
What It Is
Modern formulation that replaces some or all traditional lime with acrylic or polymer latex. Improved adhesion, elasticity, and weather resistance compared to pure cement-lime.
Material Composition
- Portland cement blended with acrylic or PVA latex
- Fine sand for texture
- Air-entraining or water-repellent additives for freeze-thaw protection
- Optional color pigments for a tinted finish
Application Method
- Single or two-coat application (more forgiving than cement-lime)
- Thinner lifts possible (1/8"–3/16" per coat) due to polymer flexibility
- Faster cure (3–5 days typical vs. 7–14 for traditional)
- Bonding agent often integrated (less prep required)
- Applied by trowel or spray (spray saves labor)
Durability in Ontario
- Expected lifespan: 15–25 years (excellent UV stability)
- Freeze-thaw performance: Excellent; polymer flexibility absorbs movement
- Salt resistance: Excellent; hydrophobic topcoat repels de-icing chemicals
- Strengths: Bonds better, more flexible, faster cure, less weather-dependent
- Weaknesses: Cost premium (15–30% higher than traditional)
Best Use Cases
New construction, aggressive climates (salt spray, freeze-thaw), substrates prone to movement, projects requiring faster turnaround, high-traffic foundation areas.
Cost Considerations
Premium pricing reflects improved durability and performance. Exact cost depends on application method, contractor expertise, and project scope. Get professional estimates for your specific situation.
Ontario Climate Recommendation
For typical Ontario foundations, air-entrained acrylic or polymer-modified parging offers the best balance of durability, freeze-thaw performance, and cost. Traditional cement-lime is excellent for heritage masonry or where breathability is critical. EIFS is ideal for ICF construction where insulation is desired.
Substrates and Surface Preparation
Long‑lasting parging starts with prep: remove loose material, failed parge, paint, dirt, and salts; treat cracks, voids, and tie‑holes first. Dampen the surface (no standing water) to reduce rapid suction. Feathering onto adjacent areas needs a rough edge and a clean, solid wall.
- Chip back to solid masonry, then neutralize efflorescence or salt bloom.
- Fill cracks/tie holes with compatible mortar or hydraulic cement so the parge is not bridging gaps.
- Mist and cool the wall in summer; warm (not hot) water helps winter applications stay workable without adding too much water to the mix.
Application Basics and Thickness
Two thin coats beat one heavy coat every time. Spread a scratch coat, let it firm up, then add the finish coat for texture. Shield fresh work from wind, rain, and freezing nights. Ontario crews stay within 10 °C to 24 °C and pause if a freeze is coming in the next day. Mist the wall for at least 24 hours so it cures evenly instead of drying out.
Thickness: Aim for at least 6 mm (¼ inch) on block walls, split into two coats so everything bonds evenly.
Bonding: Score the scratch coat and tuck mesh into corners or material changes so new cracks do not start there.
Weather: Work on calm days between 10 °C and 24 °C. If the forecast dips toward freezing, cover the wall with insulated blankets.
Integrating with Drainage and Coatings
If your project also needs a membrane or dimple board, parging usually goes on first. Let it cure, then roll on the coating and fasten the drainage board so water always moves down and out. At grade, keep soil and mulch a couple inches below the finish so it can dry.
Planning a dimple board or full waterproofing scope? Visit our foundation parging cost breakdown to see how labour, protection, and drainage tie-ins stack up on a typical GTA home.
Ontario Climate Considerations
Freeze–thaw swings, road salt, and heavy spring runoff beat up foundations fast. Southern Ontario easily sees 60–80 freeze/thaw flips each winter, so fresh parging needs at least two days of protection before it faces those swings. Keep shovels and snow blowers off the wall, run downspouts well away, and fix any negative slope so meltwater cannot sit against the surface.
Common Failures and Diagnostics
Hollow or dull-sounding spots usually mean poor prep or trapped moisture. Tap with a hammer, remove every loose patch, and start again on solid block. Cracks often come from thick coats, hot sun, or a cold snap during cure. White powder or stains mean water is sneaking through the wall and needs to be redirected.
Need a checklist for diagnosing cracks and hollow areas? Review our parging repair guide before you decide between patching and full removal.
Maintenance & Lifecycle
Walk the foundation each spring and after any brutal winter. Seal tiny chips the same week you spot them so water cannot creep behind the coat. Keep soil and mulch a couple inches lower than the finished line, slope the ground away, and rinse salt splash every March. Polymer mixes last 15–25 years when cared for; traditional cement-and-lime finishes usually run 10–15 years unless they stay bone dry.
Costs & Scheduling: What Drives the Scope
Parging projects vary significantly based on several factors. A small patch repair requires far less time and materials than a full foundation re-parge with drainage integration. Here's what affects your project scope:
- Surface condition: peeling paint, failed coats, or bonding issues add demo and prep time.
- Access & protection: tight side yards, landscaping protection, and winter hoarding requirements affect setup.
- Scope of work: spot repairs vs. full elevation coverage vs. below-grade applications.
- Add-ons: waterproofing, dimple board, drainage tie-ins, or downspout work extend the project.
- Material choice: polymer-modified mixes cost more than traditional cement but last longer.
DIY vs Professional
Handy homeowners can tackle tiny cosmetic patches. Once you see hollow sounds across a wall, stains, or anything below grade, call a pro so you are not repeating the job in spring. Pros bring hoarding and heating gear, proper mixers, and the bonding agents required to keep manufacturer warranties valid.
We\'ll inspect, document the condition, and give you a clear plan that addresses moisture and bond issues—so the new parge actually lasts.
Book a free assessmentFrequently Asked Questions
Does parging waterproof a wall?
No. Parging is a thin protective/cosmetic coat. Use dampproofing or waterproofing with drainage when liquid water or hydrostatic pressure is present.
How thick should parging be?
Ontario Building Code 9.15.6 calls for at least 6 mm (1/4") of mortar on block walls below grade. We aim for two thin coats (about 3/8"–1/2" combined) so the scratch coat keys in and the finish coat stays crack-free.
Can I parge over paint or sealer?
Only if the product allows and the coating is sound/compatible. In many cases, removal in the repair zone is required for proper bonding.
Why did my parging fail quickly?
Typical causes are poor prep, incompatible mixes, application in bad weather, or underlying moisture issues. Fix water paths and bond first, then re‑parge.
When is DIY reasonable?
Small cosmetic patches may be DIY for experienced homeowners. Widespread delamination, below‑grade scopes, or moisture problems call for a pro.
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