One of the most frequently asked questions we get at Build It Concrete is how to avoid future foundation issues such as settling, cracking, shifting, sliding or spalling. Careful study of the soil makeup and geology of the build site and proper engineering of the foundation design can greatly improve your chances of avoiding a future foundation catastrophe.
Just as in real estate, location is key to building a reliable foundation. Water is a common enemy and anywhere water seeps or flows is a potential hazard to a stable building foundation. Slope, grading, easements and drainage areas are critical to managing erosion and ensuring water flows away from the underside of the foundation. When soil is removed from under the foundation (like a mini sinkhole), settling of the home can occur and cracks in the concrete will appear. The severity of the crack is direct relation to the size of the gap between the foundation and the nearest supporting soil. Freezing water causes expansion and contraction of the soil and can stress the foundation to its breaking point.
The makeup of the top soil and bedrock are also factors in how water sheds underneath a building. Shallow foundations of a house are engineered completely different from those of relatively heavy structures like an office tower. After boring samples are taken of the soil, soil mechanics and rock mechanics are considered to determine if the site soil needs to be replaced or impregnated with other materials to adjust the composition. In severe cases, anchoring and underpinning of the foundation may be required to anchor the structure to underlying rock formations and prevent movement even during seismic events. Helical piles or piers are commonly used as anchors for deep underpinning of the foundation. If your foundation is already cracking or your home is settling we recommend consulting with http://foundationrepairportland.org to discuss options for repair. We work with Terra Firma Foundation Systems to both prepare and repair foundations in high risk areas.
There are various types of foundations to consider and a solid concrete foundation may not always be the best option depending on the soil conditions and weather elements. As mentioned, the presence of moisture in the soil or water invading areas under the home can be a recipe for future foundation issues. Raising the home off the soil is one way to eliminate the concern for expansion and contraction of soils under concrete structures when building in regions where there is frequent rain and snow. A pier and beam flooring system has many advantages and keeps direct contact of the bottom of the home off the earth. One disadvantage of a raised floor design is the crawl space under the home should be waterproofed to prevent rotting and infestation. Using synthetic building materials (plastic lumber or steel) and proper encapsulation of the crawl space can avoid long term decay and turn the crawl space into a functional storage area under your home.
Designing a basement into a home creates other challenges because the concrete walls and structure of the basement are surrounded by soil and moisture. In areas of frequent rain and snow, the thickness of the concrete walls and anchoring need to be considered. A cracking basement wall or constant seepage of moisture through the concrete walls of a basement are a sign of water management problem. Basement waterproofing, sump pumps and drainage systems are all by-products of an inherent moisture problem that may never be solved. Careful planning of the soil surrounding the basement and putting water management systems in place will mitigate severe long term damage.