Cities and counties have adopted foundation repair inspection roles in new construction and, in some cases, remodeling projects. Typically, they do this to protect the public’s health, safety, and welfare within their jurisdictions.

Foundation underpinning in existing homes involves changing the foundation type from a shallow footing system to one that converts the footing and stem wall into a grade beam supported by deep foundation elements. These are newer products that require familiarity with the systems and their ICC-ES or IAPMO reports in order to properly inspect them. Most city and county inspectors lack this expertise.

Yet the public needs assurance that the work is being done in a workmanlike manner. It must be done in accordance with a licensed design professional’s plans and be something that can be relied upon for long-term performance.

What Inspectors are Trained in and What They are Not

Most inspectors are trained in common trades such as concrete, carpentry, electrical, and plumbing. Unfortunately, they, along with many others in the construction industry, have not yet been educated in helical piers, push piers, grout injection, and similar processes.

Code requires that these products be inspected by a special inspector. This is a licensed, independent engineer or someone working under that engineer’s direct supervision and control. Per code requirements, these engineers should be hired by the homeowner, not the contractor. These engineers should be familiar with these products and their proper installation.

Items That Should Be Carefully Overseen

Matching Components

Make sure the products called out in the plans are the ones being installed. If the plans call for a specific capacity pile, the product labels should match the manufacturer’s products with that specified capacity.

Every manufacturer has a variety of retrofit brackets, sleeves, and piles, all with varying capacities. Often, a contractor may be short of a particular item needed and try to substitute in order to keep the job moving. The inspector should ensure that only the appropriate products are installed.

Since every pile manufacturer has proprietary products, the contractor should submit the intended products that meet the design criteria for approval before the job begins.

Sleeves

Sleeves are a critical item required on retrofit brackets for existing buildings. Without the sleeves, the upper five feet of the shaft are subject to buckling forces that can allow it to fail easily.

Install Logs

When helical piles are installed, torque readings are required as the pile is screwed into the soil, usually at every foot. This helps the inspecting engineer understand the soil layering and the final capacity.

If the pile “spins out,” the inspector needs to understand the soil conditions around it. If the soil is very weak, with low driving torque, and the pile hits a large rock and spins with no torque resistance, the pile is unlikely to have the capacity to support the required loads, and another one should be installed to replace it.

Similarly, if the torque forces are low and it suddenly locks up, this may also be a problem, as it may have hit a large rock or other obstruction, reducing capacity.

The contractor needs to supply the brand and model number of the drive head so that the inspector understands how to convert the hydraulic pressures to torque force per the manufacturer’s specifications. See example below.

Push piles should also have their driving pressures recorded roughly every foot for the same reasons.

At a later point, if any anomalies arise in the structure’s performance, the driving pressure logs can be examined to understand how the piles were installed. There is currently no requirement to keep logs. This needs to change.

Later, after the piles have been buried and perhaps covered with concrete paving, it is difficult and expensive to dig them up and test them. The logs provide some understanding without those costs before more invasive measures are considered.

Min/Max Depth

Piles must be driven to a depth below the zone of influence. This is the distance that water can penetrate to and potentially change the bearing capacity of the soils the piles are bearing on. Those depths vary with local soil and moisture conditions and are best understood by local geotechnical engineers. I have seen everything from 9 feet to 20 feet below the surface.

If the minimum depth is not reached, then pre-drilling should be required. I don’t know of a set maximum depth. However, costs will dictate stopping at excessive depths.

Retrofit Bracket Must Be Installed Flush

The brackets must be installed as flush to the stem wall as possible. The footing must be chipped back as close to the stem wall as possible. The bottom of the footing must be square, and the bracket installed flush to the face of the chipped-out concrete.

If the bracket is not flush, the eccentric loads on the retrofit bracket can cause failure.

Some systems that are not laterally braced, such as those that use a square-bar shaft instead of a round hollow-pipe pile, require the retrofit bracket to be bolted to the footing. Others recommend that it not be bolted. This requires familiarity with the system being installed.

You can obtain this information from the ESR or the ICC-ES report for that particular system.

Angles

Shafts should not be installed at excessive angles. No more than 2 degrees. Doing so increases the shaft’s risk of buckling.

Compacted Backfill/Coverage

After the pile has been installed, the hole dug to install it must be backfilled in lifts. It cannot all be filled at once and then compacted, as that will only compact the top layer. It should be compacted in 12-inch lifts.

Spacing Distance Between Piles

The spacing distance between piles should not exceed the spacing specified in the calculations. Typically, it will be 6–8 feet, depending on whether the stem wall is block or concrete and whether there are snow loads. Existing reinforcing will also play a significant role in the spacing calculation. Whatever spacing is specified, it should not be exceeded.

Damage Increase

It is possible that some damage could occur during pile installation. However, blanket carte blanche should not be given for any and all damage. If the cracks open up further during lifting, then the understanding of the structure’s performance is incomplete and must be reexamined.

Doweled Concrete Pads

Typically, 3′ x 3′ sections of existing concrete pavement will be removed for piles to be installed. At the conclusion of pile installation, they need to be replaced. They should be drilled and doweled on each side adjacent to existing concrete to eliminate future movement that could result in a trip hazard.

Change Orders

Often, foundation repair companies will stop during the job and say that more piers are needed. This may or may not actually be necessary. If the original repair plan was designed by a licensed professional, the likelihood that additional piers are needed is very low. But if the need arises, the special inspector or designer can evaluate the claim and determine whether the additional work is justified.

Conclusion

These products should be installed per the manufacturer’s instructions, ESRs, and technical manuals. Special foundation repair inspection by an independent engineer is crucial. That inspector should keep those records, should they be needed in the future.