Perimeter Injection
New Construction Perimeter Injection
Chemical injection for new construction is increasingly gaining popularity. The proprietary Earthlok chemical that we use is proven and effective for both new and existing foundations. Most production builders and homeowners seek to install the most cost effective foundation, this usually results in a slab on grade without piers. This may be a post tensioned slab or a concrete reinforced (rebar) slab. Either type will come with the risk of differential movement due to the swelling and shrinking nature of clay soil. There are many factors that will influence the potential movement; site preparation, stiffness of the foundation design, current moisture conditions, drainage conditions, and the natural swelling characteristics of the local soil.
By injecting at the perimeter beam prior to construction, you immediately affect the most influencing area (active zone) that will shrink/swell over the life of the foundation. We inject 6-10 feet down using high pressure hand injection steel wands. The injection is on 3ft centers directly into the perimeter beam prior to construction after the perimeter beam has been trenched by the concrete contractor. Depending on the size of the home, this process can take 3-6 hours and is performed prior to post tension cable or rebar placement.
New Construction Entire pad 6 ft hand injection
Sometimes a 10 ft injection is not warranted based on the soil conditions or not within the budget. The most active zone of soil affected by the North Texas extreme weather conditions is the upper 5-6 ft. Although the upper 12-15 ft is considered the active zone, the first 5-6 feet is more susceptible to our seasonal moisture changes from wet to dry. Each foot of clay soil depending on the plasticity index of each specific soil strata may contribute between ¼-1/2 inch of potential movement or better known as PVR (Potential Vertical Rise). If we can minimize the potential swell in the upper 5-6 ft, effectively we can alter the PVR as much as 2-3 inches. This injection is performed across the entire pad on 3 ft centers, 6 ft deep prior to any vegetation removal or site prep. At the perimeter the injection is performed more aggressively on 2 ft centers up to 5 ft beyond the perimeter. A local source of water is required using a residential hose bib retrofitted by a plumber within 50 ft of the pad.
To ensure effectiveness and to minimize inevitable concrete cracking we require a partial stress (30%) within 24-48 hrs following concrete placement if the foundation is Post tension. Additionally a preliminary grade is required following the final cable stress and cutting of the cables. A Final Grade Certification is included and required following the final grade and before sod or landscaping is installed. Slope away from the foundation should be a minimum of 5% over 10 ft, this equate to 3 inches in 5 ft, and 6 inches in 10. Consider doubling these numbers to an entire foot of fall away in 10 ft to ensure proper drainage over the life of the foundation.