Phoenix Foundation Settlement - Remediated!

Challenge

This 1951 block home was experiencing wall cracks, floor cracks as well as issues with wall separation.  The Homeowners reached out to us in order to gauge the full extent of the damage as well as proposed solutions to resolve the foundation problem.

After examining the home and performing the manometer survey, Arizona Foundation Solutions believes the home could be experiencing foundation settlement at the east and southeast portions of the home. The drop off in floor elevations on the topographical map is consistent with a foundation settlement pattern.

Foundation 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
• natural earth movement

There are also cracks in the floor slab of the home’s foundation. When the foundation 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.

Solution

We believe that the proper way to permanently stop the perimeter foundation settlement is to underpin the areas that are experiencing movement. Foundation 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 feet on center and should start and stop near the hinge points of movement (exact spacing to be determined after load bearing calculations). Lifting may or may not close the gap that was observed at the southern perimeter wall of the addition. In this case, the piles would be located at the east and southeast portions of the home.

The slab can then be treated by injecting a light weight expansive polyurethane (PolyLevel) 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 it’s Highest Practical Maximum. Using the expansive materials will help prevent additional slab settlement by compacting the upper layer of soil as it expands.

Composite interlocking can be performed to tie the broken pieces of the concrete together. The existing crack will be cleaned and non-parallel lines will be cut across the existing crack. 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.

We are also recommending a stem wall repair.  The rusting rebar found in the foundation stem wall is the result of oxidization. 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. We will add to the case study once the stem wall repair is complete. 

Project Summary

Customer Care: Shali Manuelito

Consultant: Murel Kidd

FER Tech: Jacob Walker

Design: Joelin Vistante

Engineer: Néstor J. Brea

Underpinning Foreperson: Randall Wright

Concrete Lifting Foreperson: Sarah Murillo