Piers when used are generally located at the corners of the outside forms and the future intersections of the foundation beams. Engineers generally design each pier to support around 20,000 pounds.
The strength of a foundation is derived from the beams which appear as ditches prior to pouring the concrete. Strength is calculated in two modes; they are tension (pull) strength and compression (push) strength. The tension strength is entirely due to the steel embedded in the concrete because cracked concrete has zero tension strength. The compression strength is mostly due to the concrete.
Deeper beams with more steel are stronger.
Concrete is very heavy. When the shape of a foundation or truck access limitations prevent the truck chutes from reaching all areas to be poured, concrete pumps are used for placement. The use of concrete pumps pays the dividends of better concrete uniformity because the aggregates tend to stay behind when the concrete finishers move the concrete by hand during the pour.
Ambassador has always respected the importance of a good foundation. Almost without exception all homes built by Ambassador during its history have a stronger foundation than required by code at the time of their construction.
Today’s code requires each foundation to be designed by a Registered Engineer. The engineer requires a soils report which tells him what to expect from the soil in bearing capability and expansion/contraction resulting from wet and dry weather cycles.
Foundation design has undergone considerable upgrades during the 45+ year history of Ambassador. In 1972 the city of Fort Worth accepted foundation designs drawn by plan designers with no soils information. The stiffening beams built into foundations have gone from typically 20 inches deep with 4 pieces of 1/2″ rebar steel (almost all Ambassador homes were upgraded to being built with 4 pieces of 5/8″ steel) with 40,000 psi tension strength in the 1970s. Todays foundations typically have beams 26 inches deep with 5 or 6 pieces of 5/8″ rebar steel with 60,000 psi tension strength. This is a huge increase in the required strength of foundations.
Once poured, a clod of dirt in the bottom of a beam has the effect of a notch in the edge of a 2x board. The effective depth of the beam is reduced plus a stress concentration occurs which aggravates the problem. The picture above with the “Workman’s Pride” caption shows a worker removing a clod of dirt from the bottom of the beam immediately prior to the concrete pour. This has always been a common activity during Ambassador foundation pours.