Foundation damage is by far the most expensive risk encountered when purchasing an existing home. The worst-case scenario? The engineering assessment and permits alone for major foundation repair work can easily exceed $10,000 and that doesn’t include any repairs. Repairs, such as driving piles to raise a sunken portion of a house and stitching a cracked slab back together can easily cost $30,000. Possible causes for foundation damage include improperly compacted soils, expansive soils, poor grading and drainage, sinkholes, and installation errors.
We are working hard to prevent this worst-case scenario from happening to our clients by offering a “slab foundation manometer measurement” in each of our single family home inspections where houses are built “slab on grade.” We offer this service starting at $150! Structural engineers, charging $550 and up for an initial site visit, perform a similar analysis to collect key data for their reports and repair recommendations. Please note: we are not claiming to be structural engineers but there is some overlap, and we may be able to tell you when hiring one is necessary.
As mentioned above, we will perform this manometer survey on all single family homes constructed with “slab on grade” foundations*. Modern “slab foundations” are the most common foundation and flooring system used, consisting of concrete footings and subfloor. A proper installation of a slab foundation would include levelness to within about 1/2″ from one end of the structure to the other. Excellent foundation contractors actually shoot for a perfectly level installation but in reality it’s more likely to be with within a 1/2″ tolerance.
Many potential homebuyers might be surprised to learn that nearly all inspection companies rely solely on a visual inspection to assess the condition of the foundation. Our manometer survey actually measures the levelness of the slab foundation at approximately 25 different locations – we carefully measure the finished flooring and even make adjustments at areas where the floor thickness changes. If the levelness is off by 1 or more inches then there is a good chance that there is a foundation concern. Another way to think about it this is: large slabs of steel-reinforced concrete can flex a little but after more than 1 inch of flex they will likely crack (aka “cracked slab”). If we encounter severe out of levelness a geotechnical and/or structural engineer should be consulted to investigate foundation problems.
Our engineering inspired evaluations are an easy way for our clients to know how level their home is and whether or not major repairs are needed. This helps our clients negotiate a fair price for the home they want to buy.