A proper foundation does more than just hold a house above ground. It also keeps out moisture, insulates against the cold, and resists movement of the earth around it. It should last forever. we take foundations seriously. "Without a good one, "you're sunk."
A "good" means steel-reinforced foundation walls and footings made of poured concrete. By comparison, all the laboriously assembled foundations of stone, brick, and mortar that have supported buildings for centuries—even the walls of concrete block that most builders were using 30 years ago Crack and leak
But a good foundation requires a lot more than digging a hole and pouring some concrete into forms. It must be tailored to its site like a custom suit, taking into account soil conditions, water tables, even the quality of the backfill. And as with a custom suit, every detail must be perfect: the base properly compacted, the formwork set up right, the concrete free of voids. Neglect even one of these, and the most carefully poured foundation can fail. Until a better method comes along, here's ho To build a foundation that lasts.
The weight of an average house: 50 tons
The weight of an average foundation: 60 tons
Percentage of total project cost: 8-15%
Foundations by material: 81% poured, 16% block, 3% other
Build It Right
A foundation is forever, so it makes sense to pay attention to the details that ensure it will remain dry and crack-free for as long as it has a house to hold up. When building a house, you want foundation walls that are plumb and level and free of the discolorations that are the signs of weak concrete.
The requirements for a slab foundation are similar: a sturdy footing and a vapor-proofed, reinforced-concrete pad sitting on a bed of compacted crushed stone. The major difference is in the way the slab is insulated to protect against frost heaves.
Why Foundations Fail
Nonporous backfill. Soils loaded with clay or organic matter hold water like a sponge, increasing the risk of foundation cracks when the soil freezes and expands.
Rushing the cure. Concrete must cure slowly to reach proper strength (usually 3,000 psi). Keep it damp for at least three days by wrapping it in plastic, misting with water, and other techniques.
Insufficient compacting. if the slab is poured over crushed stone that hasn't been firmly tamped, it will likely settle or crack.
Interrupting the pour. A concrete form should be filled in one go. If you stop and come back the next day to finish the work, there will be a "cold joint" between the fresh concrete and yesterday's work, which is likely to crack and leak.