When it comes to older homes in Ottawa, what’s underneath the siding can be just as important as the siding itself. Hidden structural damage, outdated sheathing, poor moisture management, and pest issues are often revealed during professional home inspections. Understanding exactly what inspectors look for behind old siding can help homeowners plan for repairs, upgrades, or full siding replacement projects with confidence.
The Importance of Inspecting Behind Old Siding
Many Ottawa homes built decades ago were constructed with materials and techniques that differ significantly from today’s building standards. Over time, exposure to harsh winters, moisture cycles, and improper maintenance can lead to hidden deterioration beneath the exterior cladding. Inspecting behind old siding is crucial for:
- Identifying concealed water damage before it spreads
- Evaluating the integrity of sheathing and framing
- Detecting mold, rot, or insulation failures
- Assessing whether the current exterior meets modern energy efficiency codes
In fact, according to Government of Canada building guidelines, older homes often lack proper air barriers and insulation layers, which directly impact energy use and indoor comfort during Ottawa’s freezing winters.
Common Sheathing Materials and Their Vulnerabilities
Plywood and OSB Sheathing
Plywood and Oriented Strand Board (OSB) have been widely used in Ottawa since the mid-20th century. While they provide structural rigidity, they are highly vulnerable to moisture infiltration if not properly protected. Inspectors typically probe these panels for soft spots, delamination, and fungal growth—signs of long-term water exposure.
Plank Sheathing
Some heritage homes feature horizontal wood planks as sheathing. While this type of sheathing is often thicker and more breathable, gaps between planks can allow moisture and pests to enter. Inspectors will examine these gaps for signs of insect nesting and check whether the structure has been updated with modern weather barriers.
Fiberboard Sheathing
Used commonly in mid-century builds, fiberboard is notorious for absorbing water. Home inspectors in Ottawa often find significant deterioration in fiberboard sheathing, especially in areas with insufficient flashing or aging siding. Once wet, fiberboard loses structural strength quickly and can contribute to interior drafts and mold problems.
Key Problem Areas Inspectors Examine
1. Wall Penetrations and Flashings
Wall penetrations around windows, doors, vents, and eaves are among the most common entry points for water. Inspectors check whether flashing has been correctly installed and sealed. Missing or corroded flashing can lead to rot within the sheathing and framing—issues that often go unnoticed until siding removal.
For example, during siding replacement, many contractors discover extensive sheathing damage around window frames due to improperly installed flashing. To understand what proper flashing looks like in Ottawa’s climate, you can review this City of Ottawa building code guide.
2. Bottom Edges and Grade Clearance
Inspectors pay close attention to the base of walls, where siding meets the foundation. If the siding or sheathing is too close to the ground, splashback from rain and snowmelt can cause persistent moisture problems. Proper grade clearance is essential to prevent rot at the sill plate and lower sheathing layers.
3. Inside Corners and Seams
Water often accumulates at inside corners where two walls meet. Inspectors look for inadequate caulking, poorly integrated house wrap, or improperly lapped siding—factors that allow water to penetrate and damage sheathing behind the scenes.
4. Eaves and Roof-to-Wall Transitions
Where roofs intersect with walls, water runoff can overwhelm siding systems. Inspectors examine these transition zones for water staining, wood rot, or signs of ice damming—a common winter issue in Ottawa homes. These areas are often where hidden sheathing deterioration begins.
Detecting Moisture, Rot, and Mold Behind Siding
Moisture Meters and Infrared Cameras
Modern inspectors use moisture meters to detect hidden dampness behind siding. Infrared cameras are also employed to visualize cold spots and moisture accumulation. These tools allow inspectors to identify sheathing issues without fully removing cladding during the initial assessment.
Probing and Core Sampling
If suspicious areas are found, inspectors may perform core sampling by removing small siding sections to directly inspect the sheathing. This technique is especially useful for fiberboard or OSB sheathing, where rot can spread internally without visible exterior signs.
Insulation and Air Barrier Deficiencies
Many older Ottawa homes lack modern house wrap or air barriers. Inspectors often find:
- Missing or poorly installed vapor barriers
- Gaps in insulation around framing
- Compressed or damp insulation batts
- Air leaks around penetrations and seams
These deficiencies lead to higher heating costs, drafts, and reduced comfort. Replacing old siding provides an opportunity to upgrade wall insulation and install proper air and moisture barriers—a step that significantly improves energy performance. For a deeper look at how siding impacts insulation performance, refer to Kaloozie Comfort’s guide on moisture management behind cladding.
Pest Infestations and Structural Integrity
Insects, rodents, and birds often exploit gaps behind aging siding. Inspectors look for:
- Insect galleries (carpenter ants, termites, etc.)
- Rodent burrows near sill plates
- Nesting in attic-wall interfaces
- Chewed insulation or sheathing panels
Even minor infestations can compromise sheathing over time. Identifying and sealing entry points is crucial before installing new siding systems.
Signs That Sheathing Needs Replacement
Home inspectors typically recommend sheathing replacement when they find:
- Extensive rot or mold patches
- Structural instability or soft spots
- Crumbling fiberboard
- Delaminated plywood or OSB
- Evidence of long-term moisture intrusion
If these issues are detected, it’s usually more cost-effective to replace the sheathing during a siding upgrade than to patch over problems. Homeowners can explore cost-effective siding options for Ottawa homes to plan accordingly.
Modern Upgrades During Siding Replacement
When inspectors uncover sheathing issues, it opens the door for comprehensive exterior upgrades, including:
- New Sheathing: Modern plywood or OSB treated for moisture resistance.
- Weather Barriers: Properly lapped house wrap to prevent wind-driven rain.
- Insulation: Adding continuous exterior foam board or upgrading batts to meet energy standards.
- Rainscreens: Creating drainage gaps to allow walls to dry, reducing rot risk.
- Flashing and Trim: Modern flashing systems that handle Ottawa’s heavy snow and freeze-thaw cycles.
For homeowners exploring the best siding options for Ottawa’s cold climate, this detailed guide covers materials that perform well in extreme weather.
Why Professional Siding Contractors Make a Difference
While DIY inspections might reveal surface-level issues, professional inspectors and siding experts have the tools and experience to uncover hidden damage. Partnering with a trusted siding contractor in Ottawa ensures that any discovered sheathing problems are addressed correctly before new siding is installed. This step not only protects the structure but also enhances your home’s curb appeal and energy efficiency.
Additionally, hiring certified experts helps homeowners comply with Ottawa’s building codes and ensures that flashing, insulation, and rainscreen details are installed properly—details that often determine whether your siding lasts decades or fails prematurely.
Conclusion: Uncovering Problems Before They Spread
Behind old siding lies the true story of a home’s condition. Ottawa’s climate, with its mix of moisture, cold, and freeze-thaw cycles, makes thorough inspections a non-negotiable step before any exterior renovation. Professional home inspections help homeowners uncover hidden structural problems, upgrade outdated components, and ensure that new siding installations perform efficiently for decades.
Whether you’re planning a simple siding refresh or a full structural upgrade, a comprehensive inspection sets the foundation for a durable, energy-efficient, and beautiful exterior. For expert help with siding inspections, repairs, and replacements in Ottawa, contact Kaloozie Comfort today to schedule a professional consultation.
