Why an Interior French Drain for Townhouses, Rowhouses, and Plexes Is the Right Solution

When it comes to protecting your home from water infiltration, choosing the right drainage system is crucial. For townhouses, rowhouses, and plexes, an interior French drain is often the most effective and practical solution. These types of properties come with unique structural and logistical challenges that make exterior drain systems less feasible—or even impossible.

Top Reasons to Choose an Interior French Drain for Townhouses

1. Limited Access to Exterior Walls

Most townhouses and plexes share foundation walls with neighboring units. This makes digging from the outside extremely difficult, if not prohibited altogether. In dense urban settings like Montreal, the space between buildings is often too narrow for excavation equipment. An interior French drain allows us to manage water from inside the foundation walls—no exterior access required.

2. Preserves Landscaping and Urban Infrastructure

With an interior system, there’s no need to demolish sidewalks, remove driveways, or dig up tightly packed urban green spaces. This means:

• No disturbing shared property lines

• No impact on mature trees or fences

• Faster installation time with less mess

3. Winter-Ready Installation

Unlike exterior systems that require ideal weather and soil conditions, interior French drains can be installed year-round, even during the harsh Québec winters. This is especially valuable if your basement is under renovation or showing signs of water damage and you need immediate protection.

4. Cost-Effective and Less Disruptive

Because excavation isn’t needed, interior drains generally cost less in labor and restoration. They also require less time to complete, which is ideal if your unit is occupied or being sold.

How It Works

An interior French drain is installed inside the basement along the perimeter of the foundation. We remove a strip of concrete floor, install a drainage pipe connected to a sump pit, and backfill with gravel. A drainage membrane is placed on the wall base to redirect any water into the system, ensuring your foundation stays dry.

This method:

• Collects water from under the slab and behind walls

• Redirects it efficiently to a sump pump

• Prevents hydrostatic pressure buildup on the foundation

Best Time to Install

The ideal time to install an interior French drain is:

• Before finishing a basement

• During major renovations

• As a proactive measure if signs of moisture or cracks appear

Peace of Mind for Urban Homeowners

Whether you own or rent a unit in a Montreal plex or rowhouse, protecting your property from foundation damage and mold is essential. At Bon-Drain, we specialize in tailored waterproofing solutions adapted to the unique limitations of urban properties.

Need a Custom Solution for Your Townhouse or Plex?

Contact Bon-Drain today for a free inspection and quote. We’ll help you choose the right system to protect your investment without unnecessary demolition or surprises.

Montreal Rowhouses