Phoenix, AZ Foundation Investigation 12.3.2021
Challenge
Homeowner’s Concerns/Goals: The Homeowner is concerned about the bathroom door in the hallway sticking, the large crack in the patio, possible tree root issues, and general cracking around the house.
The owners of this 1986 single-family home in Phoenix, AZ reached out to us after noticing several signs of a potential foundation problem. The symptoms the Homeowner noted include:
· Interior drywall cracks
· Interior ceiling cracks
· Sagging floors
A Level A Foundation Inspection indicated a need for a Level B Foundation Investigation. If needed, foundation repair recommendations will also be provided.
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 central/northern portion of the home as shown by the 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.
A minor heave pattern is observed in the southeastern 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 clayey soils, causing them to swell. The clay soils take the path of least resistance and expand upwards and lift the foundation.
There appears to be a crack in the rear patio slab. The tile will need to be removed by others to verify the slab crack. 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 stress.
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/354) exceeds the allowable deflection limit of L/360. In addition, the tilt of the slab (0.05%) was less than the allowable tilt of 1.00%.
Solution
Foundation Repair Recommendations:
A protection plan has been designed to stop the central/northern portion of the home from any possible future settlement and further damages. AZFS can permanently stabilize this area at the homeowner’s discretion.
AZFS believes the best way to stabilize the support beams in the crawl space is with Smart Jacks. These are adjustable galvanized supports engineered to be placed under the sagging floors to help prevent settlement of the floor joist system. The Smart Jack sequence should start at approximately 2’ off each perimeter wall and should not be spaced more than 7’ on center (exact spacing to be determined after load-bearing calculations). An engineered push pier will be driven concentrically beneath the beam at each Smart Jack location to provide a footing for each Smart Jack. If for whatever reason the installation of concentric piers is not possible, a concrete footing of engineered size will be poured beneath the Smart Jack to distribute the load. The Smart Jacks will then be cut to size and set in place. Finally, the units will be adjusted to lift the sagging floors back to their best functioning point or the Highest Practical Maximum.
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.
AZFS believes the crack on the rear patio is due to a control joint/marriage line in the concrete below the tile. The western portion of the patio slab is likely built on the backfill, whereas the eastern portion of the patio slab is likely built on native soil. The differential movement of the crack on the rear patio does not seem to be severe. AZFS recommends that the homeowner contact a flooring expert to remove the tile to confirm if the crack in the tile is being caused by a control joint, marriage line, or a crack in the slab.
If it is confirmed that there is a control joint or marriage line underneath the tile, the least cost alternative is for the homeowner to contact a flooring expert to see if the joint/line can be filled in and if the tile can be floated across the control joint/marriage line.
Alternatively, if the crack in the tile is being caused by a crack in the slab, AZFS recommends composite interlocking which ties 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.
Further, a protection plan has been designed to stop the rear patio of the home from any possible future settlement and further damages. AZFS can permanently stabilize this area at the homeowner's discretion.
AZFS believes that the proper way to deal with the possible minor settlement in this situation is to compaction grout or poly level the low areas in distress. Either method can be acceptable depending on homeowner goals and are summarized as follows:
• Polylevel: 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.
• Compaction Grouting: this is done by coring 2-3” diameter holes in the floor. The holes would be spaced approximately 6 to 8 feet in the center. Steel casing is driven to refusal after which low very thick cement grout is pumped under high pressure. Polylevel is very economical but does not stabilize or improve any soils that need densifying. Compaction Grouting is several orders of magnitude more expensive however it does improve and stabilize any loose soils that are in need of improvement. Prior to installing compaction grout, AZFS recommends a soil sample be performed to determine what type of grout mix would be necessary. Polylevel will not include a warranty as it does not affect the backfill soil in the same manner as Compaction Grouting.
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: This home should be looked at by a licensed Structural Professional Engineer, Professional Contractor, and/or Carpenter in order to address some of the other concerns, such as possible sagging joists in the central portion of the garage. These areas are outside the scope of work of the foundation movement analysis that was performed.
