Tucson AZ Residential Foundation Repair
Challenge
This 1979 Tucson, Arizona Ranch home was showing signs of a foundation problem. Homeowners noticed windows were sticking and getting pinched, outside concrete was out of level, exterior wall cracks, cracks in the exterior foundation as well as water finding its way into the home through floor cracks.
After examining the home and performing the manometer survey, Arizona Foundation Solutions believes the home could be experiencing foundation settlement western portion of the home as shown by the minor damage on lower floor level readings, drop off in floor elevations on the topographical map is consistent with a foundation settlement pattern. Settlement can be caused by one or any combination of many factors including sub-grade saturation of moisture due to poor drainage, years of storm runoff, plumbing leaks, improper compaction, the lack of a proper foundation system, and/or (in most cases) natural earth movement.
A foundation heave pattern is observed in the southeastern portion of the home as indicated by the higher elevation readings on the 3D Topographical Map. This phenomenon usually occurs in areas where structures are built on expansive clays. Moisture from one or any combination of the following: storm runoff, poor drainage around the foundation, plumbing leaks and/or underground moisture sources will allow the moisture/vapor to accumulate underneath the foundation. The moisture then interacts with the clayey soils, causing them to swell. The clay soils take the path of least resistance and expand upwards and lift the foundation.
There are cracks in the concrete floor slab as well. When the concrete slab cracks all the way through, the separate sections can move independently of one another. This allows for severe damage to flooring and other signs of interior stress like pinched doors, drywall, and/or ceiling cracks.
The Foundation Performance Association (FPA) “Guidelines for the Evaluation of Foundation Movement for Residential And Other Low-Rise Buildings” were adopted to correlate acceptable and unacceptable distress phenomena with actual survey elevations. Deflection and Tilt calculations were performed and compared to allowable values. For this engineered analysis, the deflection of the slab (L/586) was less than the allowable deflection limit of L/360. In addition, the tilt of the slab (0.23%) was less than the allowable tilt of 1.00%. While the tilt and deflection was less than the allowable limit, this is a general guide and the home is showing distress at areas indicating heave and areas indicating settlement.
Summary of foundation problems detected:
Solution
The foundation settlement in the western portion of the home appears to be minor at this point in time. A protection plan has been designed to stop the area from any additional settlement and further damages. AZFS can permanently stabilize this area to protect the foundation from future settlement at the Homeowners discretion.
Arizona Foundation Solutions believes that the proper way to permanently stop the perimeter foundation settlement is to underpin the areas that are experiencing movement. Underpinning is the process of installing deep foundation elements called piles. Piles are engineered foundation supports that are driven down past the unstable soils and are then locked up into load bearing strata, which can support the loads that are transferred to them. Once the piles have been installed, they can be used to lift the perimeter foundation up to it’s Highest Practical Maximum. The piles should be spaced approximately six to eight feet on center and should start and stop near the hinge points of movement (exact spacing to be determined after load bearing calculations). In this case, the piles would be located at the western portion of the home.
Arizona Foundation Solutions believes that the proper way to deal with foundation heave is by lowering and managing the moisture content of expansive clays that cause foundation heaving. It is our recommendation to manage the moisture underneath the foundation through active soil depressurization. This process will remove existing moisture from the soil as well as new moisture from the expansive clays and will help bring the moisture content down to an optimal level using both convection and evaporation. This will mitigate future heaving of the clay soil and possibly allow existing heaving to subside. This process can take six months to several years to reach equilibrium. Minor movement may still occur, as the Moisture Level® System is intended to prevent significant and continual upward movement caused by moisture.
The Moisture Level® System is designed to control the moisture of expansive clays that cause heaving under the home. If optimal results are not achieved with the Moisture Level® System including additional measures described below, more aggressive measures may be required. The manometer and foundation survey will act as a baseline to measure performance over time.
Composite interlocking – also known as concrete crack stitching - can be performed to tie the broken pieces of the concrete together. The existing cracks will be cleaned and non-parallel lines will be cut across the existing cracks. Next carbon fiber laminate stitches will be inserted into the non-parallel cuts and then the gaps will be filled with a 2 part poly. Finally, the crack should be ground smooth to minimize the differential. If done properly, this will allow the slab to function as one floating unit to help prevent the damages to flooring, ceiling and walls. If this is instead expansion joint separation, the joint should be cleaned, routed, and re-caulked with an expansive joint filler. A determination as to which repair is needed will be made on site once the crack is exposed.
Since storm runoff is responsible for the majority of the moisture that pools next to the foundation, gutters need to be installed to prevent the storm runoff from increasing the amount of foundation movement. A proper gutter system should be installed to discharge the storm runoff a minimum of 10 feet, preferably 20 feet away from the foundation. We do not recommend installing gutters that discharge next to the foundation as this will only increase the probability of a foundation problem. It is also beneficial to manage the moisture around your home using conventional means.
Project Summary
Engineer: Nestor B.
Customer Care: Sandra Hernandez
Consultant: Brian Guthrie
Underpinning Foreman: Daniel Alston
MoistureLevel Foreman: Danny Balderas
Crack Stitch Foreman: Raymundo Gutierrez
