Reinforcing a 1980's Tilt-up Building Foundation in Sacramento, CA

The Challenge

Foundation Infrastructure Repair

In Sacramento, a newly purchased office building was being converted into an elementary school. Upon inspection, the building had begun to experience signs of subsidence which the school wanted to remedy early to ensure the building’s longevity and structural integrity.

To stabilize the 1980s tilt-up building, the design engineer determined the footers needed reinforcement and to be anchored against competent strata. The original footer design included 11 exterior spread footers and 10 interior footers measuring at 6ft x 6ft x 4ft.

Key Facts

The Solution

Helical Piles Installation

The plan was to install helical piles with new construction pile caps along each of the footers and then tie them into the footers using rebar and concrete.

In order to accomplish this, Groundworks excavated a 2′ wide and 4′ deep trench to expose the perimeter and bottom of the footings. On the exterior footers 3 helical piles were installed at a minimum embedment depth of 15′ at 8,000 ft-lbs of torque, with a foundation repair bracket installed on its top. After the helical pile was installed to specification, a mesh of rebar was doweled into the footer and concrete was poured into the trench forming the footing, rebar, and helical pile into a wider and more supportive footer. 

Six of the 10 the interior footers utilized the same solution, but with a slightly different design. Around the perimeter of the column support footing, Groundworks excavated a 5′ 4″ x 5′ 4″ square at a depth of 4′ around the column. 

At each corner of the square, Groundworks installed 3-4 helical piles at 1′ x 1′ away from the edge. A grid of rebar was again doweled into the footing and concrete was poured into the trench. Additionally, 4 of the interior footers were used for brace framing used to resist seismic movement and high winds.

The Impact

Fast & Effective

The project was completed in 5 days with 71 piers installed. The building foundation was placed on a more solid footing all in time for school to adjourn without construction delays.