Every spring we start renovation projects and find the same thing in house after house: water damage that has been sitting there for months, sometimes years, hiding behind drywall, under flooring, and inside window frames.
It is one of the most avoidable problems in home ownership — and one of the most expensive when it gets ignored. We have been working in GTA homes for over 50 years, and I want to share what we actually look for before we start any interior project.
Why spring is the moment to check
Winter gives water a lot of ways in: freeze-thaw cycles crack foundation walls, ice dams back up under shingles, and improperly sloped eavestrough channels melt water right toward your foundation. By the time the snow is gone in April, whatever got in is now sitting in your walls or under your concrete. The damage is done — but you can still catch it before it gets worse and before you renovate on top of it.
What to check yourself
1. The basement floor and walls
Run your hand along the base of your foundation walls. Efflorescence — that white chalky residue — means water has been moving through the concrete. A musty smell with no visible cause usually means moisture in the slab or wall cavity. Dark staining at the base of framed walls in a finished basement is a red flag worth taking seriously.
2. Around every window on the main and upper floors
From inside, check the paint at the corners of every window frame. Peeling, bubbling, or soft drywall compound in those corners means water is getting past the exterior seal. This is especially common in windows installed without proper sill flashing — and it happens in houses of every age.
3. Your attic after a rain
If you have attic access, check the underside of the sheathing after the next rainfall. Dark staining or soft spots on the wood mean you either have a roofing issue or inadequate attic ventilation causing condensation. Both are fixable — and both get significantly worse if left alone through summer.
4. Under sinks and around toilet bases
Slow drips compound over time. Check inside every cabinet under a sink for warped wood or dark staining. At toilet bases, if there is any give in the floor when you put pressure on the tile next to the toilet, the wax ring has likely been leaking for some time.
5. Your eavestrough discharge points
Walk your foundation perimeter after a heavy rain. If water is pooling within two feet of the foundation wall at any downspout discharge, you have a grading or drainage problem. Over time this is how basements flood — not dramatically, but incrementally, season after season.
When to call a trade
Here is the general rule we use: surface staining with no active moisture source is a maintenance item you can monitor. Soft or deteriorating materials — soft drywall, soft wood, soft tile at a base — means water has been in there long enough to potentially grow mould or compromise structure. That needs a professional look before you put new finishes over it.
LF Builders has been doing waterproofing, foundation work, and exterior aluminum work in the GTA for over 50 years. If you are not sure what you are looking at, we are happy to give you an honest read. The Most Commonly Asked Questions thread is a good starting point — describe your situation and we will help you figure out whether it is a DIY fix or a trade job.
For more on spring exterior maintenance costs including eavestrough, soffit, and drainage, the LF Builders blog has a full 2026 cost guide worth bookmarking.
Have you found any surprise water damage this spring? Drop a description below — photos welcome — and we can help you identify what you are dealing with and what the next step looks like.
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