Interior drain tile for leaking basement walls
Middlesex Waterproofing lays interior drain tile, the basement French drain that sits under your slab and carries seepage to a sump.
It is the fix for water that shows up along the bottom of the walls after rain. We cut the floor along the walls, lay pipe in stone at the footing and patch the floor back.
How a perimeter system catches water at the footing
When the ground outside is soaked, water presses on the foundation from the soil side. In most basements it gets in low: the seam where the floor slab meets the wall, or the bottom of a block wall.
A perimeter system gives that water an easier way to go. A pipe sits in a stone bed down beside the footing, inside the house. Water that reaches the wall drops into the stone, enters the pipe and runs to a pit. It collects what gets through before it spreads across the floor.
Block walls, poured walls and the cove joint
The cove joint is the line where the slab was poured against the wall. The two were never bonded, so groundwater rises through that seam first.
Block walls hold water inside their hollow cores. Water fills the cores and leaks out at the bottom course. On a block wall we drill small weep holes into the lowest course so the cores drain straight into the system instead of seeping through the face.
Where water enters
- Poured wall
- Mostly the cove joint, sometimes a single crack
- Block wall
- The cove joint and the hollow cores of the bottom course
- Floor
- Cracks in the slab when the water table rises
Membrane, stone and pipe: what goes in the trench
The trench runs the length of the wet walls, close to the wall and down beside the footing. Clean stone goes in first, then perforated pipe, then more stone. A dimpled membrane stands against the base of the wall so water running down the face lands in the stone, not on the new concrete. Then the floor is patched flush.
In the trench
- Trench
- Cut along the inside of the wall, down beside the footing
- Pipe
- Perforated drain pipe, laid level or falling toward the pit
- Bed
- Washed stone around and over the pipe
- Wall
- Dimpled plastic membrane at the base of the wall
- Floor
- New concrete over the trench, finished flush
- Outlet
- A sump pit with a pump
Where the water ends up
Every perimeter pipe ends at a sump pit. The pit is a lined basin set below the floor, and a sump pump in it lifts the water out through a discharge line that runs outside and away from the foundation. If you already have a pit in a good spot, the new pipe can feed it. If not, we dig one.
The drain tile and the pump are one system. A good trench feeding a weak pump floods anyway, so we look at both on the same visit.
The path out
- 1. Wall
- Water drops into the stone bed
- 2. Pipe
- Runs along the footing to the pit
- 3. Discharge
- Out of the house, away from the wall
This is not a yard drain
French drain means two different things. A yard French drain is a gravel trench across a lawn that moves surface water. That is landscaping, and we do not take it on. What we install sits inside the house, under the basement floor.
We work from the inside. We do not do structural foundation repair or exterior excavation.
Homes on wet ground near us
Drain tile matters most where ground water sits close to basement depth. In Old Bridge, the NRCS soil survey around the township center maps Galloway and Keyport soils rated very limited for basements. In Spotswood, wet Galloway sand around the borough center sits next to muck in the low ground near Devoe Lake. In Hazlet, the Klej loamy sand mapped around the township center carries the same wet-ground rating.