Markham contractors see the same renovation mistakes over and over. Most of them are avoidable — and all of them are expensive to fix after the fact. Here are the seven that cost Markham homeowners the most money, frustration, and time on basement renovations.
Not addressing moisture before finishing
Finishing a damp basement traps moisture and causes mould. Fix water issues first — always.
Skipping the egress window in bedrooms
Building code requires an egress window in any sleeping area. Without one, the bedroom is illegal and uninsurable.
Ceiling height surprises
Many basements look adequate until ducts are moved. Measure your clear ceiling height after HVAC planning, not before.
Undersizing electrical capacity
A finished basement needs dedicated circuits for entertainment, bedroom, and bathroom loads. Don't tap into existing circuits.
Using regular drywall in high-humidity areas
Use moisture-resistant drywall throughout the basement, and cement board in the bathroom. Standard drywall degrades.
Ignoring the sump pump during finishing
If you have a sump pit, design around it — not over it. Access is required by code in most provinces.
Framing directly against the exterior wall
Always leave a thermal and vapour gap between exterior walls and framing. Direct contact causes condensation and mould.
The Bottom Line
Most of these mistakes share a common thread: they're caused by rushing decisions, skipping steps that seem optional, or choosing cost savings in the wrong places. A basement renovation starting at $31,250 is a significant investment. Spending an extra $500–$2,000 to do it right protects the other $31K+.
Use the free Markham Basement Calculator to get a realistic budget estimate before talking to contractors — knowing the real numbers prevents many of these mistakes before they start.
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