Footings, Foundations, and Slabs
Welcome to the BuildBlock ICF Installer Training Series. This 20 part video series is intended to be an educational walk through of the ICF building process. From the early planning phases to pouring concrete and finishing walls, this series will provide the basic knowledge you need to have a successful BuildBlock ICF build.
In the 6th video of the series we will identify and understand the types of foundations that ICFs are built on and discuss the advantages of each. We will also explain the basic practices of squaring an ICF project.
The videos in this series are produced as a companion to the BuildBlock Installation and Technical Manuals available for free download on the Publications Page or for purchase via the BuildBlock Online Store. You can view more videos in this series via the BuildBlock Blog or by subscribing to the BuildBlock YouTube Page. For a more in depth training experience you can take the free Online ICF Installer Training Series.
Footings, Foundations, and Slabs
In this video we’ll help to identify and understand the types of foundations that ICFs are built on. We’ll discuss the advantages of each as well as understand the basics of squaring an ICF project.
Types of Foundations
Before you select a foundation type to build your structure upon, BuildBlock highly recommends that you set up a consultation with a local structural engineer or contractors who are familiar with your region’s soil load bearing capacities.
When it comes to an appropriate base for your ICF structure, there are a several options.
- Footings are a type of shallow foundation which distribute loads from the structure directly to the ground beneath.
- Traditional Foundations, or “Deep Foundations” distribute weight bearing loads deeper into the ground. One example is the use of Pilings, which uses a tall cylinder of strong material, such as concrete, that’s pushed into the ground so that structures can be supported on top of it.
- Concrete piers are placed by drilling the approved diameter and depth of a hole into the ground on approved spacing, inserting rebar, and filling with concrete. Pilings and piers are used either when the building is very heavy (such as a high-rise structure) or when the top layer of soil is weak and loads need to be transferred to the stronger rock beneath.
- Grade Beams can be used on top of pilings and piers when the surface soil’s load bearing capacity is less than the anticipated design load. These beams consist of reinforced concrete and transfer the load from a bearing wall into spaced foundations such as pile caps, caissons, or concrete piers.
- Poured grade beams can be used without pier pilings or caissons when the soil load bearing capacity is greater than the anticipated design load.
- Lastly, Slab on Grade foundations are used when the concrete slab that is to be the foundation is formed and set directly on the ground. The slab may use post tension or have thickened edges to support the BB forms.
As you calculate the type and size of foundation, you’ll need to follow prescriptive engineering practices based on wall heights, thickness, and soil compressive strength. Also check your local codes for size requirements. You can always overbuild but you must meet local minimum requirements.
Building codes exist to define and enforce minimum standards for construction. Educate yourself on all that apply to your project before beginning. Evaluate National, State, City, and County codes as well.
Many codes are based on the International Building Code for commercial construction and the International Residential Code for residential construction. They are then refined based on local needs and requirements. Local codes will always dictate the final construction requirements.
When laying out your footings or stem walls, work with ICF friendly dimensions if possible and keep exterior finishes and flooring heights in mind. ICF friendly dimensions take into account the length and height of the ICF forms when designing wall lengths. You’ll also want to level your footings within a quarter inch or less. After stacking the first two courses shim and trim to level your footings. Be mindful of the fact that blocks will settle slightly when filled with concrete and rebar and leveling footings from the beginning will equal fewer headaches for the rest of the project.
Rebar is used to reinforce both the footings and foundations as well as ICF walls. Vertical rebar will be placed and extend from your foundation footings or stem walls and then into the walls themselves. This vertical rebar will overlap to create continuous vertical reinforcement. Make sure your rebar dowels or pins meet or exceed code requirements for wind load and backfill heights.
Ensure that rebar is correctly set in the footing and extends properly above footings for non-contact laps in walls. Rebar inside concrete must be 3 inches from any soil exposure. Rebar must be ¾ of an inch from the inside face of the foam blocks. And rebar must be 1.5 inches from other faces such as bucking. This prevents moisture from intruding into the concrete and decaying the rebar. It will also provide sufficient concrete coverage for structural integrity.
Squaring and Chalking
Square your project before staging materials. When squaring, be sure to verify that the diagonal dimensions are equal. Detailed information about squaring your project is available in the BuildBlock Installation & Technical Manual.
Lastly, place chalk lines on the footing marking the location of the outside edge of the block. Remember that the outside face of the block will be the outside face of the structure. If construction plans were not drawn for ICF, verify ICF form placement and centerlines.
In conclusion, the foundation of your ICF build is the base upon which you’re entire project rests. Therefore great care and consideration should go into each step of its creation. Building a solid foundation that is level, meeting or exceeding building codes, and reinforced appropriately will prevent costly setbacks in the building process and ultimately make the finished project strong and resilient.