How to Build a House Foundation: 7 Steps to get a Solid Foundation
Insulated Concrete Form (ICF) foundations provide a structurally sound house's bedrock, effectively transferring all the structure’s loads into the ground. An ICF foundation also firmly anchors a building or home, protecting it against extreme winds, earthquakes, and severe winds. ICF foundations also provide many other benefits, such as: energy-efficiency, durability, fire-resistance, reduced insurance rates, and ease of installation.
The double layer of continuous insulation and the high thermal mass of an ICF foundation provides a continuous air barrier with an R-value above 22, keeping a building warm in the winter and cool in the summer. ICF foundations can cut thermal conduction losses by about half.
With the application of a compatible waterproofing and/or dampproofing membrane and and a reliable drainage system, ICF protected foundation walls will eliminate moisture intrusion, which causes structural damage and unhealthy mold. ICF’s also resist termites with an application of Polyguard Products, Inc. or 650 XTP or 650 XTM membranes. Moisture and pest resistance tremendously minimizes the need for maintenance and repair of a structure.
ICF foundations provide passive fire protection, containing or slowing the spread of a fire.
Lower Insurance Premiums
The exceptional integrity of ICF foundations may lower a homeowner’s insurance premiums.
Ease of Installation
ICF foundations, particularly those constructed with Fox Blocks, tremendously benefit builders since they are fast and straightforward to build, saving both time and money. ICFs are a modular product providing over 5.3 square feet of wall per block. The insulation stays in -place eliminating any form stripping or additional labor. Temperature-resistant ICF is able to handle concrete pouring into below-grade ICFs with ambient temperatures as low as -5° F (-15° Celsius), only protecting the top of the form with insulating blankets.
7 Simple Steps to Building a Solid ICF Foundation
ICF foundation walls, like Fox Blocks, install fast and efficiently, saving time and money by lowering labor costs, eliminating the need for some subcontractors, and hastening project completion time. After placing the footings, building an average size ICF foundation should take less than a week. This includes continuous insulation, fastening strips, air barrier and vapor retardant and the addition of the waterproofing or dampproofing systems.
A Fox Blocks ICF foundation costs 20% less than either a poured concrete wall or a concrete block foundation.
1. Prepare the Footing Trench
Excavate a trench of undisturbed soil or required bearing capacity to accommodate the footers around the perimeter of the home or building site. In cold regions, you want the footings below the frost line — this prevents the frost in the winter from getting below the footers and lifting the house.
2. Build the Footings
Properly installed footings of a foundation will ensure a home’s strength and durability. The ICF footings distribute all the loads from the house to the ground.
Local building codes mandate requirements for foundation footings; however, many local code authorities use the 2018 International Building Codes (IBC) and 2018 International Residential Codes (IRC) as the model codes, modified to suit local conditions and legal requirements. ICF manufacturers may have engineering tables for the design of footing sizes following code design criteria.
The complexity of designing footings and foundation requires a qualified local structural engineer. They can specify the load requirements and footing sizing for the location of your project. A qualified structural engineer understands all the components that ensure strong footings:
- Code Compliance
- Soil Bearing Capacity and Soil Type
- Structure Loading
- Moisture Control
- Proper Reinforcing
- Frost Lines
Steps to Building Strip Footings for an ICF Foundation
Depending on the footing depth, you can use wood to form the footing. For foundation areas prone to water retention, add a drain tile system around the perimeter — this keeps the foundation dry after completing construction.
Place the horizontal rebar, as per engineering design, in the trench. During placement of concrete insert the vertical dowels in the concrete, spaced at 48" on center and protruding approximately 16" + about the concrete. The vertical dowels provide lateral support to the foundation wall as well as connect the ICF concrete to the footing.
Pour concrete directly into the trench and footing formwork. Then, screed and level the concrete. After the concrete cures, remove the wood forms, if used.
Some projects involve changes in elevation, requiring steps in the footings. For ICF construction the height of the steps should match the ICF coursing height which is typically 16". This eliminates cutting block for the whole perimeter.
For projects on bedrock, a footing may not be required. The ICF blocks may be sculpted to match the surface contours of the bedrock. Vertical dowels are still required.
Last, place gravel around the footings to encourage drainage. You can now begin installing the ICF foundations wall to the footings.
3. Installing the ICFs
Begin installing the foundation with the L-shaped corner ICFs. With each course laid, alternate the long side of the corner, creating a bonding pattern. Then, lay the straight blocks towards the center of each wall segment.
Use HV clips on the corner's webs to connect the blocks, pulling them tight. Place horizontal rebar, as per engineering design, in the clips within the block cavity, at the top of the internal webs. The clips hold the rebar, eliminating the need for wire tying.
After completing 2 block courses, use a level to confirm a horizontal level foundation wall. If not, trim to level out the wall. Once the first two courses are level and set to the building dimensions, continue laying blocks in a running bond, overlapping the courses so that interlocking blocks lock the joints from above and below. Continue this process and stack the blocks to the full height of the foundation.
After 3 or 4 courses, the installation of the alignment, bracing and scaffolding system will be required.
4. Preparing for the Concrete Pour
Tall foundation walls require anchor bracing to hold the wall straight and plumb until the concrete sets. The bracing also provides a safe framework to support scaffolding.
Place foam along the blocks' bottom to hold them down, keeping the bottom of the wall set on the building lines.
Prepare inserts, such as anchor bolts floor tie straps, hangers, etc. for inserting into the concrete at the top of the wall.
5. Pouring the Concrete
The pouring of concrete requires an experienced concrete person to ensure the wall's highest quality and integrity. Improper concrete pouring can cause a blowout, resulting in delays. Furthermore, while placing the concrete, insufficient vibrations can lessen the home’s strength, along with its resistance to air, moisture, and insect intrusion.
Using a boom or line pump, begin to place the concrete into the blocks. Apply four-feet lifts of concrete at a time, giving the concrete time to set up — this eliminates the downward pressure that can blow out the blocks.
Follow manufacturer's specifications for concrete mix design, consolidation and placement. Talk to the local ready-mix supplier about the concrete mix design for ICFs.
Vibrate the concrete during the pour to remove air pockets in the wall.
Concrete placement in a foundation would be completed in a continuous pour bottom to top of wall. Cold joints are not structural sound in a foundation wall.
6. Level the Concrete
Level off the concrete until even with the block top, then wet set anchor bolts into the concrete block top. The mudsills and top plates need to be installed and levelled, let concrete set before tightening anchor bolts.
7. Remove the Bracing
The final step is to remove the bracing and clean up the interior of the structure. Once the foundation is set and the bracing removed, you can move on to installing the waterproofing and/or dampproofing, floor system, above grade walls and interior finishes.
How Fox Blocks Can Help You Achieve a Solid Foundation
Building a solid house foundation with ICF requires qualified and experienced professionals that understand the complexities and challenges of pouring concrete. Contractors are recommended to complete the Primary installer Training provided by Fox Blocks on the Integrated Learning Center website. A properly built Fox Blocks ICF foundation ensures superior energy-efficiency, and moisture-, disaster-, and pest-resistance compared to a traditional poured foundation. Fox Blocks also creates excellent indoor environmental quality.