A raised foundation is a foundation that sits off the ground and is supported by a perimeter spread footing with interior footing pads to help support the framing of the house.
A slab-on-grade is a solid-concrete slab that rests on the ground. The grade refers to ground-level, and the slab refers to monolithic concrete pad. Slab-on-grades are most commonly used in climates that do not experience ground freezing and thawing, as this can lead to cracks in the concrete and shifting of the foundation.
Many factors influence the duration of a project, some things to consider are inclement weather, permits, change orders and sub-contractor availability. A standard 1200 square foot foundation should take roughly 2-3 weeks from start of excavation to ready for framing.
A buildings foundation can be affected by several elements and a professional will be need to properly asses the situation. With that said, some common causes for foundation issues earthquakes, water, expansive soil and outdated foundations can harm the structural integrity.
Earthquakes cause severe foundation problems. The shifting of the earth puts major strain on a foundation causing minor or major cracks. It is important to ensure your property is secured to the foundation to prevent the home from sliding off the foundation. Many older homes are not anchored to the foundation or the foundation is not deep enough into the earth. For more information on seismic retro fitting contact BDCE for further consulting and estimates.
The big issue with water/ moisture is that it causes the soil around your house to expand, while too little of it causes the soil to contract. The repeated expansion and contraction cycle put pressure on your foundation compromising the structural integrity. The freezing and thawing of moisture surrounding a foundation can cause problems. Some ways to protect your home are proper drainage (gutters and down spouts direct water away from the foundation), limit the amount of plants against foundation and keep soil grade lower to direct water away from home.
Many older homes have outdated anchor bolts, not enough bolts or no bolts at all. Anchor bolting was not strictly enforced until 1958, therefore older houses may need to be updated. Without proper anchorage a building can slide off its foundation during an earthquake or flood.
Soil types can variety depending on what county you live in. It is important to know that before starting any dirt excavation work, you should consult with qualified soils engineer that is familiar with your county.