Concrete Slab Foundation for an ADU in Boise’s North End Neighborhood
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Another Lasting Catalpa Concrete Project in Boise!
Catalpa Concrete recently completed a full slab foundation for an Accessory Dwelling Unit (ADU) located in Boise’s charming North End neighborhood.
This project involved careful site prep, coordination with utility installers, and precision formwork to ensure a stable, code-compliant foundation for a future living space.
Every phase, from layout to the final pour, was carried out with attention to detail and a commitment to long-term durability.
When it comes to the work that follows a foundation like this, we recommend PlanPro LLC, a trusted Boise ADU builder serving the Treasure Valley. They bring the same care and precision above grade that we put into every pour below it.
Site Layout and Prep
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The first step in this build was marking out the layout of the future structure. Our team used the plans to carefully stake and mark the locations of all exterior walls, ensuring the foundation would line up perfectly with the framing once it begins.
After confirming layout accuracy, we cleared the site of debris, vegetation, and any obstacles that might interfere with excavation. In-fill lot construction like this in Boise’s North End often comes with tight spaces and older infrastructure, so this phase required precision and foresight.
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Excavation and Forming Footings and Foundation Walls
With the forms in place, our next step was reinforcing the walkway using a steel rebar grid.
Rebar adds essential strength and stability to the concrete, especially in areas with shifting soil or freeze-thaw conditions like Idaho.
We installed rebar across every section of the future sidewalk, tying it securely and ensuring it was properly suspended within the forms to give the concrete long-lasting support.
Concrete Footings Poured
With excavation and formwork complete, we moved on to the first critical concrete pour: the structural footings.
These footings are the unsung heroes of the build—they sit below the foundation walls and transfer the entire weight of the future structure evenly into the soil below.
In a neighborhood like Boise’s North End, where soil conditions can vary and space is limited, properly designed and poured footings are essential to prevent settling, shifting, or future structural problems.
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Foundation Walls Finished and Forms Removed
Once the footings had cured, we returned to form up the concrete foundation walls.
These stem walls sit directly on the footings and raise the building above grade to help protect against moisture, frost, and soil movement.
Inside the wall forms, we installed vertical and horizontal rebar for reinforcement and placed embedded hardware—like anchor bolts and metal straps—to secure the future framed structure.
After careful inspection, the foundation walls were poured, vibrated for strength, and finished to spec.
Slab Prep: Foam Boards and Rebar Grid Installed
Next, we began preparing the interior of the foundation for the slab.
Rigid foam insulation was laid across the subgrade to increase energy efficiency and protect against ground moisture.
On top of the foam, a steel rebar grid was installed to strengthen the slab and reduce the risk of cracking.
Rebar chairs kept the grid elevated so it would be centered within the slab for optimal reinforcement.
This preparation met all residential and structural code requirements for Idaho’s climate and soil conditions.
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Slab Poured On Grade
With utilities, insulation, and rebar in place, we poured the slab on grade.
The concrete was pumped in and placed evenly, with our team working quickly to screed, level, and finish the surface. Utilities poked cleanly through the slab at their designated spots, and control joints were added to manage expansion and contraction over time.
The surface was smooth, strong, and ready for the next phase of construction.
