What Causes A Basement To Leak? Terrafirma

Back 1

Before we know the best way to fix the problem, lets discuss why the basement is leaking.

So this is a cross section of your home

Front 2

First the dig a big whole and pour a footing to carry the weight of your home.

When the footing is dry they pour a wall.

Back 2

When the wall is dry they pour a floor.

this is a typical 3-piece foundation: footing, wall, floor

There is an imperfect joint (Cold Joint) between the footing and the wall and the footing and the floor because they are poured at three separate times.

Front 3

On the outside of the wall they add damp-proofing (sort of like a driveway sealant)

Then they take a 3/4 inch stone and 4 inch round pipe and put it at the base of the footing all the way around the house (footing drain)

Then they backfill the hole and build the rest of the house

Back 3

The soil they excavated and put back is called loose backfill soil.

The soil in your yard, assuming no one has ever dug that soil up, is called virgin soil

Loose soil is a lot less dense than virgin soil

Front 4

When it rains outside and water comes down the hole, it flows down through loose soil more quickly and easily that it does in virgin soil.

Foot drain: the footing drain collects the water and rains the water out of the hole.

Back 4

As water comes down the hole through the loose soil, it brings little pieces of dirt with it (silt). The silt works its way through these stones.

What do you think happens to that 4 inch round pipe? (let them answer) Right?

Front 5

Let's say we took the house out of that hole; the hole would fill up with (let them answer) water.

Back 5

If we dropped the house back in the hole, it would be important to note that the water is all the way around the foundation. This is called the clay bowl effect.

Front 6

The source of the water entering the basement is the saturated backfill, sometimes referred to as a false water table.

This is what the call a vertical water column and the taller this column gets or, the more saturated this soil becomes, the more weight it has.

Back 6

If I took a jug of water and poke a hole just below the water surface how fast do you think it would come out? Right, and if i took that same jug and poked a hole in the bottom how fast do you think it would drain out? Right. Water has weight to it, there is pressure, and it's pushing down, so the taller the vertical column gets, the more press there is (hydrostatic pressure).

Front 7

so the water is going to shoot in that imperfect joint between the footing and the wall and either go under your floor, on top of your floor or both, whichever is easiest for the water to flow.

Back 7

Block walls: happens with block walls

Here is your vertical water column, and when it rains outside, the hydrostatic pressure builds, pushing water through this imperfect joint.

In the case of block walls, water usually goes up the walls a couple of feet and then shoots in on top of the floor.

Front 8

Water builds around the foundation once the drainage system fails.

If you fix any part of the basement, water takes the path of least resistance-----and finds the next weakest point of entry.

Back 8

Does that make sense?

So can you see why the basement is leaking?