How water enters your basement
The full picture, from the rain on your roof to the puddle on your floor.
The short version, in about ten seconds
Follow the water
Water doesn't need a large opening. Groundwater pressure can push moisture through some of the weakest areas of your foundation.
Swipe the diagram sideways to see the whole foundation.
Five places water gets in
Water does not need a large opening. Select a numbered point on the diagram — or a name below — to see what is happening there.
Hover, tap or use the keyboard on any marker.
The sequence
Six steps, every time
- Rain falls, or snow meltsWater arrives at the surface faster than the ground can absorb it.
- Water soaks into the soilIt moves downward through the topsoil toward the water table.
- The soil around the foundation saturatesBackfilled soil next to a foundation is looser than undisturbed ground, so it fills with water first.
- Hydrostatic pressure buildsSaturated soil pushes against the walls and up beneath the slab.
- Water finds the weak pointsCracks, mortar joints, the cove joint, the slab, and window wells.
- It appears in your basementUsually at the lowest and weakest point available.
Entry points
Where it actually gets through
Wall crack
Cracks in poured concrete or masonry can provide a pathway for groundwater.
Block / mortar joint
Water can travel through deteriorated mortar joints and cavities in masonry block walls.
Wall-to-floor joint
The joint where the basement floor meets the foundation wall is a common location for groundwater seepage.
Floor crack
Groundwater pressure beneath the slab can force moisture through cracks in the basement floor.
Window well
Poor window-well drainage can allow water to collect against basement openings.
What hydrostatic pressure means for your walls
Water weighs about 62 pounds per cubic foot. When the soil against your foundation is saturated, that weight bears on the wall continuously — and on the underside of the slab, where there's nothing but concrete between the water and your floor.
This is why sealing works so unreliably. A sealant is a thin layer on the inside face of a wall with sustained pressure on the other side. Relieve the pressure and the wall stops being a dam.
Why it's worse in spring
Frozen ground can't absorb meltwater, so it runs across the surface and collects wherever it can. Add a saturated thaw and heavy spring rain, and the soil around a foundation reaches capacity quickly. Most homeowners in this region first notice their basement problem in March or April.
Not sure which one is happening in your basement?
That's what the inspection is for. We'll look at the walls, the slab and the joint between them and tell you what we find.