When you’re budgeting a siding replacement, the cost of removing your old siding can feel like an unnecessary expense. Why not just put the new panels right over the old ones? Some contractors are happy to quote it that way — it’s faster, you save on disposal, and the price looks better at first glance.
But there are important reasons why most experienced Calgary contractors recommend against it. Here’s the full picture.
When Siding Over Siding Is Technically Possible
Let’s be fair — there are scenarios where siding over existing cladding can work:
Scenario A: Single flat vinyl layer, no moisture damage If your home has one layer of flat, undamaged vinyl in good structural condition, it can act as a flat substrate for new siding — in theory. The existing panels need to be nailed flat and not warped.
Scenario B: Aluminum siding in good condition Older aluminum siding that is flat and properly nailed can be sided over in some cases. The flatness and structural stability of aluminum are better than aged vinyl.
The key qualifications:
- No moisture damage behind the existing siding
- Single layer only (multiple layers create too much thickness and unevenness)
- Window and door jamb extensions can accommodate the added thickness
- The manufacturer of the new product permits this installation method
Even in these scenarios, removal and inspection is still preferable. Let’s explain why.
Why Removal Is Almost Always the Better Choice
1. You Can’t Inspect What You Can’t See
This is the most important point. Calgary’s climate creates real and common moisture issues behind siding:
- Failed caulking around windows allows water intrusion
- Ice damming from freeze-thaw cycling drives moisture under the bottom course
- Hail damage to existing panels creates micro-cracks that admit moisture
- Missing or degraded house wrap allows condensation buildup
When you side over existing cladding, you’re permanently covering the wall sheathing without inspecting it. Any existing moisture damage continues progressing, now hidden under two layers of cladding. In 5–10 years, when the problem becomes severe enough to manifest externally, you have a much more expensive problem.
In our experience installing siding throughout Calgary, a significant percentage of re-sides reveal some degree of moisture damage, soft sheathing, or missing house wrap when the old cladding comes off. Some are minor; some are extensive and would have been catastrophic if left in place.
2. House Wrap Is Usually Due for Replacement
Building paper and house wrap systems from the 1970s–1990s are commonly compromised on Calgary homes of that era. When you do a proper re-side with removal, you install fresh house wrap — a critical moisture management layer that protects your wall system.
Siding over the old cladding means your wall is protected by aging, potentially degraded building paper. Even if the new siding keeps bulk water out, air-driven moisture and thermal bridging issues from old house wrap are real.
3. Uneven Substrate Creates Installation Problems
Old siding that is warped, buckled, or has wavy sections creates an uneven surface for the new installation. New panels installed over this uneven surface will:
- Ripple and flex rather than laying flat
- Have gaps between the panel back and the substrate
- Look wavy from the street
- Provide less wind resistance than properly backed panels
4. Added Thickness at Windows and Doors
Every layer of siding adds thickness to the exterior wall. Window and door frames extend only so far from the sheathing — adding a new siding layer requires extension of window jambs and door casings. Contractors who side over existing material without addressing this create a situation where:
- Window trim is recessed relative to the new siding surface
- Water can accumulate at the window-siding intersection
- New trim is required regardless, adding cost
When you factor in the required window and door trim work, much of the removal cost savings evaporates.
5. Manufacturer Warranty Implications
Both James Hardie and LP SmartSide have explicit installation guidelines that govern warranty validity. Installing over existing siding is typically not a covered installation method. If your new fiber cement or engineered wood siding has a problem in year 7, the warranty claim investigation will look at how it was installed — and a non-compliant installation can void coverage.
The Cost Reality
The argument for siding over existing siding is almost always financial. So let’s look at the actual numbers:
Cost of removal (average Calgary bungalow):
- Old vinyl or aluminum removal: $800–$1,500
- Stucco removal: $2,000–$4,000 (more labor-intensive)
Cost of NOT removing (potential future costs):
- Discovering moisture damage in 5–10 years: $3,000–$15,000+ depending on extent
- Stripping two layers of siding for repair: higher than stripping one
- Replacing window and door trim improperly extended: $800–$2,000
The removal cost is a defined, bounded expense. The cost of hidden moisture damage is unbounded.
Our Recommendation
At King’s Land Siding, we recommend full removal on virtually every re-siding project. We price it into our quotes, document what we find underneath, and address any wall assembly issues before new siding goes on. That’s what a responsible installation looks like.
If you’ve been quoted a siding-over-siding installation, ask the contractor these questions:
- What is your rationale for not removing the existing material?
- Does the manufacturer of the new product permit installation over existing siding?
- What happens if you find moisture damage after starting work?
- Is the workmanship warranty the same as for full removal?
If the answers aren’t satisfactory, consider getting a second opinion. Call King’s Land Siding at (403) 555-0190 or request a free estimate.
