Foundation Investigation in Scottsdale, AZ 12.2021

Thursday, December 2nd, 2021 by Jessica LaFlesch

Challenge

Homeowner’s Concerns/Goals: The Homeowner is primarily concerned with the cracks on the exterior of this 1960’s block home.

An initial, Level A Foundation Inspection noted several symptoms of a potential foundation problem, including:

· Floors out of level

· Drywall cracks

· Windows sticking / pinched

· Outside concrete out of level

· Cracks in the exterior walls

· Cracks in the exterior foundation (concrete stem wall).

A Level B Foundation Inspection was needed to determine the root cause of the noted symptoms.

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

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 foundation settlement at the southwest portion of the home as shown by the damage (aka Signs of Stress) and lower readings on the 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 north and northwest portions of the home and at the northern and southeastern portions of the garage as shown by the minor damage (aka Signs of Stress) or lower readings on the Topographical 2D Map.

A minor foundation heave pattern is observed in the central portion 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 clay soils, causing them to swell. The clay soils take the path of least resistance and expand upwards and lift the foundation.

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/546) was less than the allowable deflection limit of L/360. In addition, the tilt of the slab (0.03%) was less than the allowable tilt of 1.00%.

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 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 southwest portion of the home. 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. If the addition was not properly permitted, then the recommended repairs may have to wait until the city issues a permit.

The foundation settlement at the north and northwest portions of the home and at the northern and southeastern portions of the garage 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 Homeowner's discretion.

AZFS does not suggest a heave repair plan at this time as there is no significant damage to correspond with the high elevation readings. The home should be monitored and should damage arise in the future, AZFS should be contacted to perform a comparative manometer survey at a discounted price.

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. 1f 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