Combination Waterproofing Strategies: When Mixing Products Backfires

The Cost-Saving Temptation

Castleford’s question represents a common dilemma for Canadian homeowners: Blueskin peel-and-stick membrane provides excellent protection but costs significantly more than brush-on alternatives. The proposed solution—using Blueskin only where “needed” at the critical footing/wall joint, then switching to cheaper brush-on waterproofing above—seems logical but contains a fatal flaw.

The Proposed Strategy

• Blueskin from footing up 2.5 feet
• Brush-on waterproofing from there to grade
• Delta dimple mat over everything
• Perimeter drains to daylight

The Question: “Does anyone think the water would/could make it under the blueskin?”

The Answer: Yes, absolutely—and here’s why.

The Reverse Lap Problem

Akos’ Critical Insight

“All peel and stick membranes need to be terminated at the top. What you are proposing is technically a reverse lap.”

This single sentence identifies why the combination approach fails.

Understanding Reverse Laps

Normal Lap (Shingle Effect):

• Upper material overlaps lower
• Water flows over joints
• Gravity aids waterproofing
• Standard installation practice

Reverse Lap (Problem):

• Lower material ends mid-wall
• Upper material below termination
• Water can enter at transition
• Gravity works against you

Why This Matters

Water running down the wall hits the transition between products:

1. Flows behind brush-on coating
2. Reaches top edge of Blueskin
3. Infiltrates under membrane
4. Defeats entire system

The expensive Blueskin at the critical joint becomes useless once water gets behind it from above.

The Physics of Water Movement

How Water Defeats Mixed Systems

Path of Least Resistance:

• Water seeks any available pathway
• Transitions create vulnerabilities
• Adhesion differences matter
• Capillary action draws water in

Product Incompatibility:

• Different expansion rates
• Adhesion challenges
• Chemical interactions
• Aging differently

The Termination Challenge

Proper Termination Requires:

• Mechanical fastening
• Compatible sealants
• Transition strips
• Perfect execution

Adding these elements eliminates any cost savings from the mixed approach.

Real Cost Analysis

The False Economy

Castleford’s Thinking:

• Save money using Blueskin only where critical
• Brush-on product for less critical areas
• Dimple mat protects everything

Akos’ Reality Check: “The amount of extra work for this half/half setup will probably cancel out the savings”

Hidden Costs of Combination

Additional Materials:

• Termination bar for Blueskin
• Compatible sealant
• Primer for transitions
• Extra labor time

Risk Costs:

• Potential failure points
• Warranty complications
• Future repairs
• No single-source responsibility

Time Investment

Single Product:

• Continuous application
• Consistent technique
• Predictable timing
• Simple inspection

Mixed Products:

• Stop/start at transition
• Different application methods
• Careful termination work
• Complex quality control

Better Alternatives

Option 1: Full-Height Peel-and-Stick

Akos’ Recommendation: “If you are worried about water, than go with a full height peel and stick. Simpler and guaranteed to work.”

Advantages:

• Single product system
• No transitions
• Full warranty coverage
• Proven performance

Cost Mitigation:

• Shop for bulk pricing
• Consider off-season purchase
• Look for contractor surplus
• Evaluate total lifecycle cost

Option 2: Full-Height Brush-On

If Budget Truly Constrained:

• Use quality brush-on throughout
• Apply proper thickness
• Multiple coats at cold joint
• Reinforce with fabric

Key Requirements:

• Premium elastomeric product
• 60+ mil thickness
• Careful surface prep
• Professional application

Option 3: Address the Cold Joint Specifically

Peter Yost’s Advanced Solution: “If you are really worried about the cold joint between the footing and the foundation, there is a solution for that: waterstops”

Waterstop Options:

• Bentonite waterstops
• Rubber waterstops
• Crystalline products
• Injectable systems

These address the specific vulnerability without compromising the wall system.

Understanding Product Hierarchies

When Blueskin Makes Sense

• High water table sites
• Critical below-grade spaces
• Poor drainage conditions
• Long-term reliability needed

When Brush-On Suffices

• Good drainage in place
• Moderate water exposure
• Accessible for maintenance
• Budget constraints

When Dimple Mat Alone Works

• Excellent drainage
• Low water exposure
• Temporary protection
• Belt-and-suspenders approach

The Cold Joint Focus

Why Castleford Worries

“I don’t trust the brushon stuff down at the footing where the concrete blocks form a seam”

This concern is valid—cold joints represent the weakest point in foundation waterproofing.

Addressing Cold Joints Properly

During Construction:

• Waterstop installation
• Keyway formation
• Bonding agents
• Careful concrete placement

Retrofit Options:

• Bentonite rope
• Crystalline treatments
• Injection grouting
• Surface-applied systems

Product Selection for Cold Joints

Best Performers:

• Self-adhering membranes
• Bentonite products
• Flexible cementitious
• Multi-component systems

Poor Choices:

• Rigid coatings
• Thin applications
• Non-flexible products
• Solvent-based materials

Making the Right Decision

Decision Framework

Choose Single Product When:

• Warranty matters
• Simplicity valued
• Long-term thinking
• Professional installation

Consider Combinations Only When:

• Different wall conditions
• Transitioning existing systems
• Temporary solutions
• Expert guidance available

Castleford’s Best Path

Given the Canadian climate and expressed concerns:

1. Invest in full-height Blueskin

   • Single-source solution
   • Proven cold-weather performance
   • Addresses cold joint properly
   • Simplifies installation

2. OR commit to quality brush-on

   • Select premium product
   • Apply generously at joint
   • Consider fabric reinforcement
   • Accept some risk

3. But avoid the combination

   • Reverse lap issues
   • False economy
   • Increased failure risk
   • Complex installation

Lessons from the Field

Why Contractors Propose Combinations

Well-Intentioned Reasons:

• Client budget concerns
• Targeting known problems
• Using leftover materials
• Regional practices

Problematic Motivations:

• Unfamiliarity with products
• Cutting corners
• Inventory management
• Competitive bidding

Red Flags to Watch For

Warning Signs:

• “Just as good” claims
• No termination details
• Dismissing reverse lap concerns
• No warranty discussion

Good Signs:

• Explains termination requirements
• Discusses single-product benefits
• Offers waterstop alternatives
• Provides written warranties

Technical Best Practices

If You Must Combine Products

Absolute Requirements:

1. Upper product overlaps lower
2. Proper termination details
3. Compatible chemistry
4. Mechanical termination
5. Sealant integration

Installation Sequence:

1. Install lower product full height first
2. Apply upper product with proper overlap
3. Never reverse the lap
4. Document everything
5. Test thoroughly

The Dimple Mat Factor

What It Does:

• Provides drainage plane
• Protects waterproofing
• Reduces hydrostatic pressure
• Adds redundancy

What It Doesn’t Do:

• Fix waterproofing failures
• Eliminate proper terminations
• Replace quality products
• Solve reverse lap issues

Cost-Saving Strategies That Work

Legitimate Ways to Save

1. Optimize Coverage

• Buy correct quantities
• Minimize waste
• Proper surface prep
• Efficient application

2. Enhance Drainage

• Invest in better drains
• Free-draining backfill
• Surface water management
• Reduce hydrostatic pressure

3. Strategic Protection

• Dimple mat where needed
• Protect during backfill
• Proper compaction
• Avoid damage

4. Timing Purchases

• Off-season pricing
• Bulk discounts
• Contractor relationships
• Regional suppliers

Conclusion

Castleford’s instinct to protect the critical cold joint is correct, but the proposed combination strategy creates more problems than it solves. The reverse lap issue identified by Akos represents a fundamental flaw that no amount of careful installation can overcome.

As Akos wisely notes, the extra work required to properly terminate and transition between products eliminates any cost savings. Worse, it introduces failure points that compromise the entire system.

The recommendation is clear: choose a single waterproofing strategy and execute it well. Whether full-height Blueskin or quality brush-on product, consistency trumps combination. If the cold joint remains a specific concern, address it with purpose-built solutions like waterstops rather than compromising the entire wall system.

Key Takeaways

1. Reverse laps create failure points - Water will find the transition
2. False economies cost more - Repairs exceed initial savings
3. Single products simplify - Installation, warranty, and performance
4. Cold joints need specific solutions - Not partial coverage
5. Expert advice saves money - Akos prevented a costly mistake

Final Recommendation

Castleford’s ultimate decision to “go with the full Blueskin then” represents wisdom gained from expert input. The slightly higher initial cost provides:

• Peace of mind
• Single-source warranty
• Proven performance
• Simplified installation
• Long-term value

In waterproofing, as in many construction decisions, trying to save money by mixing systems often costs more in the end.

Resources

• Cold Joint Waterproofing Solutions
• Peel-and-Stick Membrane Installation
• Waterstop Technologies
• Cost-Effective Waterproofing

For expert waterproofing solutions that balance cost and performance in Toronto, call (437) 545-0067