Poured Concrete Foundations
Poured concrete foundations are the most common type of foundations found on modern houses today.
Normally for residential construction the foundation thickness may vary between 8 inches to 10 inches thick and built on a concrete footing 10 inches thick by 30 inches wide with double rebar reinforcement depending of the bearing capacity of the soil where the foundation is to be built.
A common mistake by builders is to proceed without having a ground test done by an engineer to verify the ground capacity to bear load.
With proper calculation , a foundation can be built with the right footing size or other methods like helicoidal piers prior to pouring.
Not doing so may cause foundation problem in the future such as ground settlement that will cause cracks in the foundation, foundation drop, cracks in drywall, windows and doors not closing properly and uneven floors to name a few.
A proper evaluation at this point need to be done by a professional to evaluate the condition of the foundation and what it is needed to be done to correct and protect your foundation.
Common poured concrete foundation issues and solutions
Cracks need to be fixed and waterproofed to avoid water damage, structural damage and insects invasion.
Polyurethane Injection: Polyurethane injection is used to create a seal to protect from water infiltration and stay flexible in order to absorb further movement
The crack has to be covered with hydraulic cement and holes are made on each side of the crack to receive the injection tip.
Polyurethane is injected at 3000psi into the crack at 12 inches apart to cover from bottom to top.
Depending on the size of the crack, one or two steel belt reinforcement may be needed to give structural value to the repair.
A steel belt is secured to the foundation with 6 x 5 /8 concrete anchor bolt, 3 on each side of the belt and protected with a rubberized membrane.
Multiple cracks and foundation settlement
Multiple cracks and foundation settlement may be caused by multiple factor such as:
- Improper footing size
- Type of soil built on ( clay )
- Built on backfill material improperly compacted
- Vegetation to close to the foundation such as trees with excessive water absorption
- Drought season on clay soil
To correct a foundation that encounter that type of problem , it is necessary to transfer the load of the foundation on piles and lift the whole structure to its original level.
The process consist in installing braces under the footing, bolted to the foundation and push steel piers in the ground until we reach bed rock or refusal.
When the piers are in place, hydraulic jacks used to lift the house to its original level and secured into place.
Water infiltration may come in various ways.
- Concrete defect at pouring
- Rusted steel rods
- By capillary or hydrostatic pressure
In situations where the water infiltration is generalized , it is recommended to use Polyurethane injection and steel belt for cracks repair and also a membrane covering the whole foundation below grade.
A french drain would be installed at the base of the footing to control hydrostatic pressure and directed by gravity to a dry pit or sump pump pit
This installation is recommended for houses 20 years old and older.
If existent, after 20 years, the french drain have a big chance to be clogged up with dirt and inoperant, causing hydrostatic pressure at the base of the foundation .
In that situation you will observe water or humidity marks at the junction of the concrete floor and the foundation.
Another sign of hydrostatic pressure is the presence of efflorescence on the concrete. Efflorescence is a white powder deposit on the concrete found generally at the base of the foundation or on the concrete floor.
It is caused by the water migration through capillary and evaporation process at the surface of the concrete.
As the water migrate through the concrete it carry with it minerals and leave it at the surface creating a deposit.
When exposed for an extended period of time the concrete becomes porous and loses its original capacity and strength.
Keeping water away from your foundation will prevent deterioration and will give you a better quality of life.
Mildew and Fungus
Mildew and fungus will prosper in humid area.
Health wise it is recommended to pay an immediate attention and to correct that problem. To eradicate successfully mildew and fungus, you have to address the cause.
In order to do so , it is imperative to control the humidity level and to have a proper ventilation.
It is recommended to install a french drain and a membrane on the foundation.
For crawl space on bear ground, a sealed vapor barrier on the ground must be installed in addition to the drain and membrane and create a proper ventilation ( natural or mechanic) in the enclosed area of the crawl space.
Advanced foundation deterioration
Foundation deterioration may be caused by poor concrete quality or poured in freezing condition without protection.
Foundation that has been exposed to water reach a point of no return and need to be replaced.
The old foundation have to be removed and replaced by a new one.