Co-written by Bob Brown and David Deatherage, PE

One of the best forensic geotechnical engineers I know, Dave Deatherage, suggested adding this section to the list of items to be included and gathered as part of the forensic evaluation. I agreed and added this to my list, and accordingly, I asked him for input into this blog and am sharing the credit with him. 

Why Interviewing Homeowners is Crucial for Foundation Analysis

Like a doctor getting vital information from a patient to help diagnose a condition, interviewing homeowners for foundation analysis can provide insight into past actions that may impact our understanding of the building’s current condition and any signs of movement. 

For example, was the drywall or stucco patched by a professional? Most repairs are easy to spot, but if done by a skilled professional, like those hired by builders, they can be much harder to notice.

The same goes for door frames or windows that have been replaced, floors that have been re-leveled, or new baseboards installed. When we don’t see these signs, we might initially discount certain conclusions. However, knowing that repairs or replacements have been made allows us to adjust that assessment accordingly.

Sometimes, important events help explain the data we’re observing. I remember one case where a homeowner mentioned late in the process that a leaking meter at a critical corner of the house explained the elevated readings in that area, which had expansive soil. This, combined with poor drainage in the other three corners, helped us make sense of the data.

This is a subtractive floor-level reading. Notice how the corners have risen between the two readings over time. The leaking water valve was at the southeast corner of the garage.

Context and Information Gathering

I remember in this particular case, a foundation repair salesman told the homeowner there was a giant void in the middle of the slab that needed $30,000 worth of Polyurethane foam injection. What a disaster that would have been in those very expansive soils!

Even small repairs, like fixing a landscape junction box or line, can have an impact. Additionally, if a tree has been removed, the roots no longer draw water from the soil, which can also affect the foundation.

I remember one homeowner who made a sustainable choice by replacing their grass lawn with desert landscaping. Apparently, this lawn had been overwatered for many decades. When the change was made, the soil then dried up, causing the front of the house to settle by over 3 inches.

Sometimes, this kind of information can significantly affect a proposed repair plan. In one instance, I discovered after starting a job that the fill under the home was large cobbles! Well, it would have been nice to know that ahead of time, as that would make the installation of helical piles ineffective. 

Additions to a home are also critical. If there are plans for that addition or remodel, even better. Often, additions are not built on the original prepared pad, and the dirt work may only involve trenching for footings, which could lead to settlement or heave, depending on the conditions.

Often, when additions are built, the footing and slab are poured together monolithically and typically without a spread footing underneath. This is important because, without that spread footing, push piles won’t function properly, and helical piles should be used instead. It’s crucial to know this ahead of time, so materials aren’t brought to the site only to be exchanged later.

Checklist for Interviewing Homeowners

Dave Deatherage suggested the checklist below to gather critical homeowner input during interviewing homeowners for foundation analysis.

Some other items of valuable homeowner input include:

• Age of home? (can be checked on Zillow)
• How long has the current owner lived in the home?
• When did the owner first notice distress?
• What repairs have been made?
• Has repaired distress reoccurred?
• Were there any prior problems or repairs disclosed at the time of the most recent sale?
• Do you have a floor plan?
• Any history of water or waste line leaks?
• Does any portion of the lot have flood irrigation?
• Does the home have a septic system with a leach field?
• Is there ponding of runoff during storms?
• Are there any other forensic reports on the home?
• Can you get a copy of the original geotechnical report, site grading and drainage plans, earth fill compaction testing results, and foundation design drawings?
• Is the slab post-tensioned?

In a podcast of the Civil Engineering Academy, I discussed how, as part of their oath to protect public welfare, engineers should supervise projects and work to minimize change orders for homeowners. Part of that due diligence is to gather this kind of data that will result in fewer surprises during construction.  

Context is everything. The more information we have, the better we can interpret observations and create constructible plans that avoid unnecessary changes.