1950s Cement Block Foundation Complete Restoration
North York, Toronto April 2024 Total Cost: $14,500 Duration: 5 Days
The Challenge
This 1950s North York home with hollow-core cement block foundation experienced severe water infiltration through deteriorated mortar joints. The homeowner had attempted DIY repairs with hydraulic cement, which failed within months. Water was entering through multiple points, causing mold growth and threatening $30,000 worth of finished basement renovations.
Foundation crack caused by winter freeze-thaw cycles - a common issue in block foundations
Property Details
Home Specifications
- Built: 1953
- Foundation Type: 8" hollow-core cement blocks
- Basement Size: 1,200 sq ft
- Foundation Perimeter: 140 linear feet
- Depth Below Grade: 7 feet
- Soil Type: Clay (poor drainage)
Water Issues Identified
- • 40% of mortar joints deteriorated
- • Step cracks in 3 corners
- • Water filling hollow block cores
- • Efflorescence on 60% of wall surface
- • Failed DIY patches in 8 locations
- • Mold growth behind drywall
Initial Assessment Findings
Critical Issues Discovered:
- Mortar Joint Failure: Original lime-based mortar from 1953 had reached end of life. Joints were soft, crumbling, and allowing direct water penetration.
- Hollow Core Water Accumulation: Water was filling the hollow cores of blocks, traveling internally, and emerging at floor level 10+ feet from entry point.
- No Waterproofing Membrane: Original construction had only parging, which had delaminated in multiple areas.
- Inadequate Drainage: Original clay tile drain was 70% blocked with sediment.
- Grade Issues: Landscaping had raised grade, directing water toward foundation.
Our Solution: Comprehensive Interior & Exterior Approach
Phase 1: Interior Waterproofing (Days 1-2)
- • Removed 18" of drywall along perimeter to access foundation
- • Drilled weep holes at base of hollow cores to drain trapped water (87 holes total)
- • Installed WaterGuard® interior drainage system along 140 linear feet
- • Connected drainage to new TripleSafe™ sump pump system with battery backup
- • Applied crystalline waterproofing coating to interior block walls
Phase 2: Critical Repairs (Day 3)
- • Repointed deteriorated mortar joints with Type N mortar (420 linear feet)
- • Injected polyurethane into step cracks (3 locations, 18 linear feet total)
- • Core-filled bottom 3 courses of blocks with concrete for stability
- • Installed carbon fiber strips at corners for reinforcement
Phase 3: Exterior Protection (Days 4-5)
- • Excavated problem areas (north and east walls, 70 linear feet)
- • Applied rubberized membrane to exterior block surface
- • Installed dimple board drainage mat for additional protection
- • Replaced sections of weeping tile and connected to interior system
- • Backfilled with 3/4" clear gravel and proper grading
Dimpled membrane properly installed at the base of the footing for optimal drainage
Technical Specifications
Materials Used
- • 140 ft WaterGuard® drainage channel
- • 1 TripleSafe™ sump system
- • 180 Ah battery backup system
- • 8 gallons polyurethane injection resin
- • 35 bags Type N mortar mix
- • 4 yards concrete for core filling
- • 700 sq ft rubberized membrane
- • 700 sq ft dimple drainage board
- • 12 yards 3/4" clear gravel
Equipment Deployed
- • Mini excavator (Kubota KX040)
- • Concrete saw for interior trenching
- • Core drilling equipment
- • Injection pump (2000 PSI)
- • Industrial dehumidifiers (2 units)
- • HEPA air scrubbers for dust control
- • Mortar mixer and pumping equipment
Cost Breakdown
| Component | Cost | % of Total |
|---|---|---|
| Interior drainage system | $4,200 | 29% |
| Sump pump with battery backup | $2,500 | 17% |
| Mortar joint repairs | $2,100 | 14% |
| Crack injection | $1,200 | 8% |
| Exterior waterproofing (partial) | $3,500 | 24% |
| Concrete restoration | $800 | 6% |
| Permits and disposal | $200 | 2% |
| Total Project Cost | $14,500 | 100% |
Financing: Homeowner used 12-month 0% financing. Monthly payment: $1,208
Complete waterproofing and insulation system for optimal foundation protection
Results & Follow-Up
Immediate Results (First 30 Days)
- Complete elimination of water infiltration
- Basement humidity dropped from 78% to 45%
- No water accumulation during April 2024 storms (4.2" rainfall)
- Mold remediation successful with no regrowth
6-Month Follow-Up (October 2024)
- System handled fall storms without issues
- Sump pump cycling normally (4-6 times daily during rain)
- No new cracks or mortar deterioration
- Homeowner completed basement refinishing ($18,000 investment)
Current Status (3 Years Later)
- Zero water infiltration events
- Annual maintenance performed (pump cleaned, battery tested)
- Home value increased by $45,000 (appraiser noted dry basement)
- Insurance premium reduced by $280/year
Lessons Learned
Key Takeaways from This Project:
- Hollow block foundations require special attention: Water trapped in cores must be addressed with weep holes and proper drainage.
- DIY repairs often make problems worse: Improper hydraulic cement application trapped water inside blocks, accelerating deterioration.
- Combined approach most effective: Interior drainage handles groundwater while exterior protection prevents infiltration.
- Mortar joint maintenance critical: Repointing every 25-30 years prevents major structural issues.
- Early intervention saves money: Addressing issues before basement finishing saved estimated $20,000 in remediation costs.
Homeowner Testimonial
"After trying to fix the water issues myself for 2 years, I finally called Dryspace. They identified problems I never knew existed - water was traveling through the hollow blocks and emerging far from where it entered. The crew was professional, explained everything, and cleaned up daily. Three years later, our basement is still bone dry. The peace of mind was worth every penny, especially after we invested in finishing the basement. Our home value increased significantly, and we even got an insurance discount. I wish I had called them sooner!"
Similar Foundation? Here's What You Should Know
If your home has a cement block foundation (common in Toronto homes built 1940-1970), watch for these warning signs:
- • White chalky deposits (efflorescence) on block surfaces
- • Horizontal or step cracks following mortar lines
- • Water appearing at floor level with no visible source above
- • Deteriorating mortar that crumbles when touched
- • Musty smell even after dehumidifying
Early intervention typically costs 50-70% less than waiting until severe damage occurs.
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