Preventing Moisture Intrusion: A Home Inspector’s Guide
Written by Mike S. Avelar, CPI
Moisture intrusion is one of the most common causes of damage in homes. It leads to mold, structural issues, and costly repairs if left unchecked. Fortunately, most moisture problems start small — and homeowners can prevent them with simple, regular checks around the exterior.
Below are the key areas to monitor to keep water out of your home.
Planters and Landscaping Near the Foundation
Planters and raised garden beds can trap water against your home’s exterior. When soil stays wet for long periods, moisture can seep into hidden areas of the structure.
What to watch for:
- Planters installed directly against exterior walls
- Soil or mulch piled too high against siding
- Water pooling inside raised beds after rain
Planters act like small dams. They hold water in place, which increases the chance of moisture penetrating the foundation or wall assembly. Ideally, keep all planters away from the home’s exterior and ensure the soil slopes away from the foundation.
Puddles and Standing Water
Standing water is a red flag. It indicates poor drainage and can lead to foundation leaks, settlement, and erosion.
Check these areas regularly:
- Beneath decks, porches, and cantilevered structures
- Around sprinkler zones
- Along walkways and patios
- Near exterior walls
The ground should slope away from the home. Low spots or settled backfill allow water to collect next to the foundation, increasing the risk of moisture intrusion.
Gutters and Downspouts
Gutters and downspouts play a major role in directing water away from the home. When they’re misaligned or clogged, water ends up exactly where you don’t want it.
Key points:
- Downspouts should discharge away from walkways, driveways, and stairs
- Homes on hillsides should drain downspouts on the downhill side
- Use splash blocks or paved drainage chutes to prevent soil erosion
- Consider connecting downspouts to an underground storm drainage system if available
If your home doesn’t have gutters, roof runoff can cause damage below. Gravel beds or paved drainage channels may be needed to manage the water.
Flood Zones and Local Requirements
If your home is located in a flood‑risk area, additional precautions may be required to protect your foundation, basement, and surrounding property.
What to do (Ottawa Homeowners):
- Check your flood zone using GeoOttawa The City of Ottawa provides detailed, interactive flood‑risk mapping. Visit: https://maps.ottawa.ca/geoottawa/ Turn on the Flood Plain layer to see if your property is within a regulated flood zone.
- Review local building requirements Municipal and provincial regulations often include stricter standards than national guidelines. These may include elevation requirements, drainage controls, or restrictions on basement development in high‑risk areas.
- Consult conservation authorities In Ottawa, floodplain regulations are typically overseen by:
These agencies provide guidance on development restrictions, grading requirements, and flood‑risk mitigation.
Why this matters
Flood‑prone areas may require:
- Elevated floors
- Reinforced structural components
- Engineered drainage systems
- Restrictions on additions or basement modifications
Improper grading can worsen flood hazards, leading to erosion, sediment buildup, and water intrusion into basements or crawlspaces.
Final Thoughts
Moisture intrusion is preventable when homeowners stay proactive. By monitoring landscaping, drainage, gutters, and local flood requirements, you can significantly reduce the risk of water damage.