A - Cracks without shearing or toppling.

a) It is a crack without shearing or toppling meaning that there is certainly no need for piles as there are no sinking.

In the study of what those cracks represent!
In the clicked enlargement, it can be seen that, if both side are aligned horizontally, both sides of the teeth would fit like a in a gear.	In this corner crack, it can be seen that the crack developed on the side wall and not on the back wall. It can also be seen that the crack goes away from the ground of the back of the house where the oil delivery pipes are. Also, the ground level is much lower beside the back wall than on the side wall and that runoffs accumulate much more there than on the side wall, The ground, by freezing and heaving more on the back does heave more in the back and has created the crack on the side wall.

a) Vertical cracks, even if they are very small "hair line" size are cracks right through, outside to inside cracks.

In this case, the slopes are inverted and send the runoffs of the down spouts of the eves and of the surrounding land toward the foundation.
It can be seen that the crack does not even extend to the brick wall. But, humidity and runoffs from the roof and surrounding ground follow the foundation.	Some of it enters the crack that is right through.	And appears in the basement garage.

Note: See the section on the strength of concrete, even if there is cracks in the foundation.

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CONCLUSION

The most important part of this section is the importance that there is a positive slope to keep runoffs away from the foundations.

The importance to raise / embank earth berms around buildings so as to keep water away from foundations and avoid cracks, mainly for insulated foundation walls.

Resume

So, what must be done to avoid humidity and water in basements?

If eventually humidity or water appears in the basement

a) Unhook the down spouts of the eves from any pipe or drain underground.

b) Install elbows and out of ground extensions to the down spouts.

c) Get rid of all low ground or crushed stone against the foundations.

d) Add top soil or clay, even heighten the sod around the building, against the foundations to change the negative slopes going in the direction of the building to positive slopes toward the street and property lines.

e) If the basement window sills in the concrete foundation are too low to be able to embank the soil all around the house, add basement window wells.

f) lastly, if this is insufficient, install a sump pump with a depth of at least 27" to 30" inch deep. Deep enough to bring down the water table ( phreatic table) under the basement slab in order that when the pump starts at the high control level, the water level under the slab be at least 6" inch lower.

g) To dig around the house to change the foundation, (French drains) around the house serve nothing if the above points are not respected. In the majority of cases, it is not that the foundation drains are blocked; it is that the drains are overflowed with more than 10 times too much water and have been wet for 10, 20, 30 years or more.

Eventually, humidity or water appears through the porous concrete of the foundation. (1/2" inch per year)

Important data:

The four (4) down spouts coming from the eves at the four (4) corners are almost of the same dimension of four inch installed near the foundations.
In addition, during intense rainfalls, a vertical pipe gives three time more flow than an accordion shaped pipe installed horizontally.

Four (4) down spouts X three (3) times more flow = twelve (12) more flow than the capacity of the foundation drain.
If in addition the runoffs flows of the lot and of the surrounding land are added, it is impossible that a foundation drain suffice.

Second important data:

The "French" foundation drains should NEVER be used as a pluvial evacuation sewer or drain pipe. If it is done, see here what happens: window sills Click me!

Foundation drains are used mainly to dry-up the soils before the freeze-up of winter to avoid formation of cracks in the foundations, mainly if they are properly insulated.

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