Tucson Foundation Investigation: Revisit
Challenge
Homeowner’s Concerns/Goals: The prior read was performed in June of 2020; the Homeowner requested a reread to make sure the stress has not gotten worse. The Homeowner is concerned about the cracks on the walls and the horizontal stem wall cracks.
Introduction: Thank you for allowing Arizona Foundation Solutions to present this foundation survey and assessment for the proposed foundation repairs on your property.
Purpose of the Investigation: The purpose of this report is to evaluate the foundation and the foundation conditions at this property, and to perform a manometer floor survey Re-Read 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 foundation survey and assessment are detailed as follows:
• Perform a Re-Read Manometer Survey.
• Visually inspect both the interior and the exterior of the location.
• Determine the extent of the difference between initial read and re-read.
• Prepare a Topographical Map of the reading differences.
• 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 for any major additional damage or signs of stress from our previous recordings. In addition, the previous recommendations were reviewed and verified if they had been followed (proper grading, drainage, gutters or no gutters, and removal of any large trees too close to the foundation). Interior Inspection: The interior of the location was also visually inspected and compared to the previous recordings.
Manometer Survey: A Manometer was set and new data points were taken from the same locations as the original readings. The entire interior floor area was surveyed and the elevations were recorded. The new data points were compared to the original data points and then entered into a computer program providing a new topographical map. The following information is included in the report:
• Original Data Points
• Original Topographical Map
• New Data Points
• New Topographical Map
• Subtractive Topographical Map
After examining the home and performing the manometer survey, Arizona Foundation Solutions believes the home could be experiencing foundation settlement at the Living Room and Kitchen of the home as shown by the damage on (Previous and New Signs of Stress) and lower readings on the New Topographical 2D Map. The 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.
AZFS believes the home could be experiencing minor foundation settlement at the Master Suite, Dining Room, and Laundry Room as shown by the minor damage (Previous and New Signs of Stress) and lower readings on the New Topographical 2D Map.
The rebar in the stem wall along certain sides of the home has begun to rust. This has caused the rebar to deteriorate and the iron oxide to expand. The expansion from the iron oxide generates enough pressure to crack the stem wall. The corrosion of the bar has to typically exceed 20% before there is enough pressure to crack the stem wall. This issue should be dealt with properly to prevent the corrosion from spreading down the perimeter of the rebar and to return the original strength and span capacity to the stem wall.
It appears that some stress on the home may have been exacerbated by the removal of concrete at the front patio.
Solution
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 perimeter of the Living Room and the Kitchen. The slab can then be treated by injecting a lightweight expansive polyurethane to fill existing voids and lift the floor slab. This is done by drilling small 3/8” holes in the slab after which polyurethane grout is injected directly under the slab to raise it up to its Highest Practical Maximum. Using the expansive materials will help prevent additional slab settlement by compacting the upper layer of soil as it expands.
A protection plan has been designed to stop the Master Suite, Dining Room, and Living Room from any possible future settlement and further damages. AZFS can permanently stabilize these areas at the homeowner’s discretion.
Arizona Foundation Solutions believes that the rusting rebar in the foundation stem wall needs repair. The stem wall must be chipped back to expose the corroded rebar. The rebar should then be cut out and replaced with a composite bar and dowelled to bridge the separation between the bars. The stem wall should then be patched and finished smooth. This will prevent the treated area from future rust and restore the ability of the stem wall to span small voids and support the load. It is recommended to wait at least one week before painting the surface of the stem wall.
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
