New Construction Mistake: Insulation Installed Before Roof in Winnipeg
- Mar 21
- 2 min read
🏠 New Construction Doesn’t Mean Done Right: Insulation Installed Before the Roof?
By 365 Home Inspection – Winnipeg
Walk into a new construction home and you expect things to be done right… right?
Not always.
Recently, I came across a build where:
Insulation was already installed in the walls
The roof wasn’t even on yet
Snow had made its way inside the structure
At first glance, some might not think much of it. But from an inspection and building science standpoint—this is a serious red flag.
❄️ Why This Is a Problem
When insulation is installed before the building is weather-tight, it becomes exposed to the elements.
And that creates real risks:
💧 Moisture Intrusion
With no roof in place, snow and moisture can enter wall cavities. Fiberglass insulation can absorb that moisture, even if it doesn’t look soaked.
📉 Reduced Thermal Performance
Wet insulation = reduced R-value.
That means the home may never perform as efficiently as intended—leading to:
Higher heating costs
Cold spots
Comfort issues
🦠 Mold & Hidden Damage
Moisture trapped behind finished walls can create the perfect environment for mold growth.
And once drywall is installed?
👉 You won’t see the problem anymore.
🔒 Trapped Moisture Behind Vapour Barrier
Modern homes rely on vapour barriers to control moisture movement.
But here’s the issue:
Vapour barriers are designed assuming insulation is dry at installation
If moisture is already present, it can get trapped inside the wall assembly
That’s where long-term durability problems start.
📘 What the Manitoba Building Code Says
Manitoba follows the National Building Code of Canada (NBC), and this situation goes against the intent of several key sections:
🔹 NBC 9.25.2.1 – Protection of Materials
Building materials—including insulation—must be protected from moisture during construction.
🔹 NBC 9.25.3 – Installation of Thermal Insulation
Insulation must be installed in a way that maintains its effectiveness.
Wet or compromised insulation does not meet this requirement.
🔹 NBC 9.25.4 – Vapour Barrier
Vapour barrier systems are designed to work with dry, properly installed insulation within a sealed building envelope.
⚠️ The Bigger Issue
This isn’t just about one house.
It’s about construction sequencing and quality control.
Installing insulation before the roof is in place:
Shows poor planning
Increases risk of hidden defects
Can impact the home long after it’s finished
🧠 “But It’s Brand New…”
That’s the mindset that gets people into trouble.
New doesn’t mean perfect.
New doesn’t mean problem-free.
And new definitely doesn’t mean it was built properly behind the walls.
🔍 Why New Construction Inspections Matter
This is exactly why I always recommend inspections—even on brand new homes.
Because issues like this:
Won’t be visible later
Won’t be disclosed
And can cost homeowners down the road
💬 Final Thoughts
Insulation exposed to snow before the roof is installed isn’t just a minor oversight—it’s a sign that corners may be getting cut.
Smarten up, builders. This stuff matters.
📍 Serving Winnipeg & Surrounding Areas
📞 204-396-3161
365 Home Inspection
Built. Not boosted.
Comments