Laying the foundation for a new building is a crucial first step in the construction process. A properly constructed foundation provides a stable, durable base that prevents settling and keeps the structure secured.
The foundation laying process involves extensive site preparation, precise formation of foundation walls, proper reinforcement, and careful pouring and curing of the concrete. Each phase must be completed thoroughly and methodically to produce a level, crack-free foundation.
In this article, we will walk through the foundation construction process step-by-step, from initial site clearing to final grading around the completed foundation. Following the proper sequence of steps and utilizing the right techniques and materials lays the metaphorical and literal groundwork for the rest of the building project.
Before the foundation can be constructed, the site needs to be prepared. This involves clearing and leveling the land. Any trees, bushes, large rocks, or debris need to be removed. The topsoil is then stripped away so that the foundation can be built on solid ground. The area is leveled using heavy equipment like bulldozers and graders. The soil is compacted to provide a stable base. Proper drainage systems like catch basins may be installed at this stage to prevent water accumulation under the foundation.
Once the site is prepared, the outline of the foundation is set out. This is done by a surveyor using stakes and string to mark the perimeter of the foundation based on the plans. The stakes indicate the exact position of the foundation walls. Batter boards are erected outside the foundation to attach string lines, which act as guides for the foundation walls. The string lines ensure the walls are built straight and at the proper dimensions.
Trenches are dug along the outline marked by the string lines. Excavators and backhoes are typically used to dig the foundation trenches. The trenches need to be dug wide enough to allow formwork to be erected and deep enough to extend below the frost line. The frost line depth varies by location but is typically 1-3 feet below grade. Going below the frost line prevents frost heaving, which can crack and shift the foundation. Proper slope and drainage should be established in the trench bottom.
Formwork refers to the temporary structures that hold the concrete in place as it hardens and cures. Formwork is erected using large wooden or steel panels that are braced into position along the foundation trenches. The forms need to be built sturdy and watertight to avoid leaks. The top of the formwork is set at the desired height of the foundation wall, typically 8-12 inches above grade level. The forms will be removed once the concrete has hardened sufficiently, usually after 1-2 days.
Steel rebar reinforcement is added inside the formwork to strengthen the foundation. Rebar rods are cut to size and laid out in a grid pattern within the trench. The rebar needs to be raised off the bottom using Dobies or wire. Proper rebar spacing and overlap are necessary per code requirements, typically 6-12 inches. Rebar helps resist cracks and lends tensile strength to the concrete. In some cases, fiber reinforcement is added to the concrete mix instead of rebar.
Any anchor bolts, hold-downs, or other embeds needed to secure the structure to the foundation are installed at this stage. Anchor bolts are placed at regular intervals around the perimeter of the foundation according to the building plans. Bolts and embeds need to be secured properly so they don't move when the concrete is poured. Templates may be used to position the bolts accurately.
With all formwork, rebar, and embeds in place, the foundation walls and footings can be poured using ready-mix concrete. The concrete should be poured continuously to prevent cold joints. Vibrators are used to consolidate the concrete and remove air bubbles. The concrete is screened off and smoothed with a trowel for a clean finish. Control joints are tooled into the concrete to regulate cracking as it cures. The entire pour needs to be protected from rain or freezing temperatures as it sets.
The forms remain in place for 1-2 days to allow the concrete to gain sufficient strength. Then, the formwork can be "struck" or removed carefully. Most companies vibrate or loosen the forms to dislodge them. Form ties sticking out of the concrete are bent back or snapped off. Repairs are made to any holes, blemishes, or honeycombs on the surface of the concrete. Curing continues for several weeks before backfilling.
The trenches around the foundation are backfilled with clean fill dirt once the concrete has cured adequately. The backfill is compacted in layers to brace the foundation walls. A plastic vapor barrier can be applied to the exterior of below-grade walls before backfilling. Drain tiles are installed around the footer and connected to a sump pump to control groundwater. Finally, waterproof sealants are applied to the foundation walls for moisture protection.
The last step is to bring in additional fill dirt and topsoil to establish the final grade around the completed foundation. The soil needs to slope away from the building at a minimum 5% grade. This prevents water from pooling near the foundation. Landscaping features like ground cover and gravel help improve drainage. Proper site grading is critical for keeping moisture from penetrating the foundation.
That covers the basic process for laying and preparing a new building foundation step-by-step. Paying close attention to each phase results in a structurally sound, long-lasting foundation that supports the building safely. A quality foundation prevents future cracks, leaks, and settlement issues.
About Bloomington Foundation Repair Experts
With over 20 years of dedicated service, the Bloomington Foundation Repair Experts deliver top-tier results. Each technician is licensed, certified, and skilled in repairing, building, and inspecting concrete slab and pier & beam foundation systems. To schedule an appointment, please call (309) 220-3907.
What needs to be done before pouring a foundation?
Before pouring a foundation, the site needs to be fully prepared by clearing vegetation, stripping topsoil, and compacting the soil to create a stable base. Formwork then needs to be constructed, with reinforcement steel and anchor bolts properly installed within the formwork. Finally, utilities such as plumbing and electrical conduits that interface with the foundation need to be accurately positioned prior to the concrete pour.
How long does it take to lay down foundation?
The time required to lay a building foundation depends on factors like the size of the project, soil conditions, and weather, but it typically takes 1-3 weeks. A small residential foundation may only take a few days, while larger commercial projects can require several weeks to fully prepare the site, install formwork, reinforcements, and utilities, pour the concrete, and allow proper curing time before backfilling.
How long after a foundation is poured can you build?
Before building, it is recommended to allow the poured concrete foundation to cure for a minimum of 7 days to gain sufficient strength. Many codes require 28 days of curing time before constructing walls or the frame. It is best practice to backfill around the foundation and complete any waterproofing or damp-proofing applications before erecting walls or the structure to avoid damaging the foundation.