Gilbert, AZ Level B Foundation Investigation
Challenge
Homeowner’s Concerns/Goals: The homeowner is concerned about the slab crack that runs through the dining room.
The owners of this 1994 Gilbert, AZ home reached out to Arizona Foundation Solutions after noticing several symptoms of a potential foundation problem. An initial, Level A Foundation inspection determined that a Level B Foundation Investigation may be needed to determine the root cause of the foundation movement.
Purpose of the Investigation: The purpose of this report is to evaluate the foundation and the foundation conditions of this property, and to perform a manometer and foundation survey on the interior of the property.
Limitations: The purpose of this report is limited to documenting and addressing the areas of concern indicated by the customer related to potential foundation movements. Arizona Foundation Solutions uses a variety of tools such as manometer survey, observations by technicians with notes and photographs, and industry standards such as the Foundation Performance Association (FPA) “Guidelines for the Evaluation of Foundation Movement for Residential and Other Low-Rise Buildings” to determine if foundation movement has impacted the serviceability of the home. The term serviceability relates to items such as pinched doors and windows, cracks in drywall and slabs, cracks in exterior stucco and walls, and the like. Recommendations in this report are made to address and limit future issues related to serviceability and the customer’s concern.
The extent and scope of this manometer and foundation survey and assessment are detailed as follows:
• Perform a manometer survey.
• Locate areas of potential foundation and floor movement if any.
• Visually inspect and record the interior and the exterior of the location.
• Evaluate any noted movement using industry consensus methods if any.
• Prepare a documented repair plan if needed.
Foundation Footprint: A drawing of the footprint of the first floor was created and is included in this report.
Exterior Inspection: The exterior of the location was visually inspected. Items such as foundation cracks, exterior wall cracks, improper grading, type of structure, poor drainage, gutters or no gutters, bowed retaining walls, large trees close to the foundation, and any type of obstructions that may or may not influence the repair process were noted and recorded.
Interior Inspection: The interior of the location was visually inspected. Items such as floor cracks, wall cracks, ceiling cracks, sloping floors, uneven countertops, doors and windows that are out of alignment, cracked window glass, and bowed walls were noted and recorded.
Manometer Survey: The manometer survey, also known as a floor survey, is a measurement of the differences in interior floor elevations. The flatness of the interior floor was measured using a highly accurate survey device known as a Manometer. The entire interior floor area was surveyed, and the elevations were recorded. These data points were then entered into a computer program that provides a topographical map showing the high and low elevation contours of the floor surface. This topographical map shows where the foundation is no longer level and shows where support and stabilization are needed. The floor survey also demonstrates whether any floor slab heave or settlement exists.
After examining the home and performing the manometer survey, Arizona Foundation Solutions believes the home could be experiencing minor foundation settlement at the southwestern portion of the home as shown by the damage on the Signs of Stress. 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 minor heave pattern is observed in the central and eastern portions of the home as indicated by the higher elevation readings on the Topographical 3D 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/appear to be cracks in the floor slab. The flooring will need to be removed by others to verify the slab cracks. When the 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/555) was less than the allowable deflection limit of L/360. In addition, the tilt of the slab (0.07%) was less than the allowable tilt of 1.00%.
While the tilt and deflection were less than the allowable limit, this is a general guide and the home is showing distress at areas indicating heave and areas indicating settlement.
Solution
A protection plan has been designed to stop the southwestern portion of the home from any possible future settlement and further damages. AZFS can permanently stabilize this area at the homeowner’s 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 its Highest Practical Maximum. The piles should be spaced approximately six to eight feet on the 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 southwestern corner 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 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 the 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® Smart Foundation System is intended to prevent significant and continual upward movement caused by moisture. The Moisture Level® Smart Foundation 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® Smart Foundation 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 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 two-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 unit to help prevent 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. The homeowner may want to contact a flooring expert and consider floating the flooring after the repair has been made.
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 as outlined below:
• Hire a reputable plumbing leak detector and repair service to check both pressure and sewer lines, this is usually done for less than $500. If repairs are needed, they are usually not expensive.
• Make sure the grading of the terrain is sloped downwards at a 5% slope from the home at all areas of the perimeter.
• Stop irrigating plants that are near the foundation and make sure there is nothing trapping the moisture from flowing away from the home.
• When permanently stabilizing, lifting, and/or mitigating a foundation movement problem, AZFS recommends waiting AT LEAST 6 months before investing in cosmetic repairs.
Safety or Structural Concerns: None
Project Summary
Engineer: Néstor J. Brea
