{"id":5339,"date":"2025-04-08T09:36:50","date_gmt":"2025-04-08T04:36:50","guid":{"rendered":"https:\/\/marcoreparationdefondation.com\/?p=5339"},"modified":"2026-10-07T22:55:44","modified_gmt":"2026-10-07T17:55:44","slug":"french-drains-vs-interior-drainage-systems-which-is-better-for-basement-waterproofing","status":"publish","type":"post","link":"https:\/\/marcoreparationdefondation.com\/en\/french-drains-vs-interior-drainage-systems-which-is-better-for-basement-waterproofing\/","title":{"rendered":"Interior or Exterior French Drain: Which Should You Choose?"},"content":{"rendered":"

The right drain depends on two things: what is wrong with your current drain, and whether crews can dig around the house.<\/strong> According to CAA-Qu\u00e9bec, a faulty exterior drain is normally handled by an excavation contractor, while an interior drain is considered when excavating outside is difficult or impossible. In Quebec, the term “drain fran\u00e7ais” (French drain) means the drain that runs around the footing, so this guide compares the exterior drain with its interior alternative.<\/p>\n

The facts below come from CAA-Qu\u00e9bec’s guide R\u00e9parer un drain r\u00e9sidentiel ou une fondation<\/a>, the APCHQ Performance Guide<\/a> (edition consulted: 2006), the City of Qu\u00e9bec’s page on sump pump systems<\/a> and the City of Montr\u00e9al’s R\u00e9noPlex rate table. All are in French.<\/p>\n

What Is the Difference Between an Exterior and an Interior French Drain?<\/h2>\n

The exterior drain sits outside the foundation, at the footing, and carries groundwater away from the wall. The interior drain sits inside the basement, under the slab edge, and sends the water it collects to a sump pit where a pump removes it.<\/p>\n\n\n\n\n\n\n\n\n
Question<\/th>\nExterior drain<\/th>\nInterior drain<\/th>\n<\/tr>\n<\/thead>\n
Where is it?<\/td>\nAround the footing, outside the wall<\/td>\nInside the basement, along the slab perimeter<\/td>\n<\/tr>\n
How is it done?<\/td>\nCleaning, partial repair or full replacement, which requires excavation<\/td>\nThe slab is cut over about 12 in. along the perimeter, a drain and gravel are laid, the walls get a drainage membrane and the slab is poured back<\/td>\n<\/tr>\n
When is it chosen?<\/td>\nWhen the exterior drain is faulty and the ground can be excavated<\/td>\nWhen excavating outside is difficult or impossible<\/td>\n<\/tr>\n
Pump needed?<\/td>\nDepends on the house<\/td>\nYes, the trench connects to an interior sump pit with a pump<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

When Is Exterior Drain Work the Right Route?<\/h2>\n

When the existing drain is crushed, clogged or sagging and the ground around the house can be opened. CAA-Qu\u00e9bec advises hiring an excavation and landscaping contractor, who can diagnose the problem with an optical camera and then choose between three levels of work: hydro-jet unclogging, repair of one section, or full replacement. A full replacement means excavation, several weeks of work and, according to the guide, waiting until the following year for the final landscaping.<\/p>\n

The APCHQ sets the standard for a new build: the French drain must meet the code in force and work so that no water gets into the basement. It adds that a camera can assess a drain’s general performance, and that some water sitting in a drain is perfectly normal and does not mean it is failing. CAA-Qu\u00e9bec puts the normal lifespan of a drain at about 40 years.<\/p>\n

When Does an Interior Drain Make Sense?<\/h2>\n

When excavating around the house is difficult or impossible, CAA-Qu\u00e9bec says an interior drain can be considered. The trade-off is that it depends on a pump. The guide asks for an annual check: test the pump, remove debris and test the backwater valve. It also warns about radon and recommends an airtight lid on the sump pit, which also helps against odours and insects.<\/p>\n

Two points to settle before choosing this route:<\/p>\n