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SANDY: As education and awareness for our readers, Tom and I feel it is important to inform our community on soils reports, also known as geotechnical engineering reports. One big change: effective this past January 2016 for unincorporated Yavapai County only, “It shall be the responsibility of the PROPERTY OWNER to provide a Geotechnical Engineering Report at the time of permit application for all habitable structures.
Tom: The definition of a habitable structure is: Single family residences, manufactured/modular/factory built and park model homes secured to a permanent foundation, additions to single family residences over 400 square feet in size, guests houses, all livable accessory structures and detached structures that require a registered design professional (engineer or architect) and, of course, any appropriate permits are required.
Sandy: There are exceptions to this requirement and they are: Attached patio covers, deck (covered or open), and additions to habitable structures under 400 square feet are exempt from these requirements. The Building Inspector and/or the Chief Building Official for Yavapai County Development Services can waive this exemption if the site conditions warrant recommendations from a Geotechnical Engineer.
Tom: This is important information to know: If a Geotechnical Engineering Report exists for a property, it is the responsibility of the PROPERTY OWNER to contact that engineer/engineering company to ensure the report includes all proposed structures. Buyers of vacant land in unincorporated Yavapai County should be encouraged to investigate soils conditions upon considering purchase of property in order to adequately project development costs.
And also it would be beneficial to anyone building a new home to investigate, sample and test the soils prior to permit and construction to determine their physical and engineering characteristics of the soil. You should know what you are building on!
Sandy: In Arizona, our biggest worry is our soil, which can cause problems with the foundations of our homes. Fortunately, most problems caused by bad soil can be repaired. A lot of soil-related problems arise because homeowners assume living in a dry climate means the soil is dry, sandy and stable, so they do not think twice about planting and watering near the house. In many areas of the state, the soil contains a high percentage of clay, meaning it is neither sandy nor stable. In fact clay-based soil expands when it gets wet and shrinks when it dries. Soil is moisture-sensitive, and as long as it is dry, there is no problem. Water changes everything. As soon as moisture fluctuates, during a monsoon storm or if you plant a yard full of thirsty greenery, the problems begin. When clay-rich soil comes in contact with water, it expands, causing the soil particles to push upward. If that happens right under your house, it can damage your foundation. Expansive soil is among the most expensive geologic hazards and causes $300 million a year in damage to homes. Building codes do not assure long-term performance (settlement or heave values within industry standards) of the fills, footings and floors. We can only assume that you all want to build a good, well-performing building.
Tom: Sandy, what does a soils report address?
Sandy: The report will address the conditions of the soil where development is proposed. This information is imperative when considering the foundation design of the structure, as depending on conditions, significant foundation engineering may need to be performed. A soil engineering report will present a picture of what the intended project will consist of; recommendations to be used by a structural engineering for footing depth, width, bearing pressure, estimated settlements, heave potential, etc. A soils report also presents to civil engineers site grading requirements, minimum ground slopes, minimum permanent cut and fill, etc. The report contains a description of the site and soil conditions so the builder will now what they will have to contend with.
In short a soils report is the “how to design and build recipe for the foundation structure” that goes on the site. When followed the design will result in a successful, long-term performance of the home.
Tom: I have been involved in situations where substandard soils have been discovered upon inspection of foundation footings and the builder was required to cease construction until the soils issue could be mitigated. This has resulted in unexpected costs to the builder and homeowner and unnecessary delays in the project.
SANDY: Tom, you are absolutely correct, failure to mitigate substandard soils can result in complete failure of a structure. Buyers of vacant lands in the unincorporated areas of Yavapai County should be encouraged to investigate soils conditions upon considering purchase of property in order to adequately project development costs.
SANDY: Some of the problems associated with expansive soils include: foundation cracks, cracks in floor slabs and walls, jammed doors and windows, ruptured pipes and cracks in sidewalks and roads. Not all soil is Arizona is expansive. Some is collapsible, which means it is loose and dry, and will collapse and compact when it gets wet. This kind of soil can cause your home to settle rather than heave, but the symptoms are similar to the heaving brought on by expansive soils, cracked foundations, floors and walls.
Tom: Recently, a four-year-old home started to heave such that there was more than three inches of differential floor movement from one side of the house to the other. Subsequent remediation revealed that the soils consisted of a medium to high plasticity clay soil. The maximum soil movement occurred under the bearing footings on the southerly side of the house where exposure to rain, snow and the yard irrigation water was the highest. Remediation efforts consisted of: installation of helical piers under house footings, removal of the entire flor slab, temporary support of interior non-load bearing walls, removal of two feet of the clay soils from within the entire building footprint, removal of eight inches of clay soil from below the base of the foundations, installation of a low-density foam between the clay soil and the footing base, installation of non-expansive floor fill, replacement of concrete floors. Cost to repair: $250,000, as compared to a soil investigation report at approximately $1,600 if one had been performed prior to building on the lot.
Swelling soils cause damage to thousands of homes every year. The extent of the damage varies from cracked driveways and sidewalks to severe structural deformation.
SANDY: Tom, our population is growing and as the population continues to move into the outer reaches of communities, many times project sites become more and more marginal. These sites can be built upon, but it is critically important to address the long-term performance of the home on the lot and build to a “higher” industry standard by obtaining a Geotechnical Engineering Report on your lot before you build.
SANDY: Tom, as a realtor, when you have buyers purchasing a home I know that you share the importance of looking for signs of “heaving” or “settling” which could indicate there is evidence of active foundation movement. Minimal settling cracks are common, but an inspection by a licensed concrete foundation specialist will help identify if there are other items of concern.
SANDY: For new homeowners looking to purchase a home and current homeowners, there are several practices that will allow you to grow a landscape that complements your home, while avoiding the potentially damaging effects of swelling soils and perhaps mitigate the damage to your home.
Tom: When landscaping your home, plant vegetation no closer than five feet from the foundation, unless the plants have very low water requirements. Xeriscape-type groundcovers and mulches are especially useful near houses because they can help reduce extreme moisture fluctuations. Don’t allow sprinkler systems to spray any closer than five feet from the foundation, and plant trees no closer than 15 feet from the foundation. Another tip is to make sure all water drains away from the foundation and there is proper slope to the yard.
Thanks for stopping in “At Home with Tom and Sandy.” You’re in good company and we love sharing important information with you. See you next month. QCBN