To level a concrete block foundation, especially on a sloped site, you use solid-concrete blocks of varying thicknesses on the low end to raise it to the same level as the high end. This method compensates for the natural grade of the ground, creating a level base for subsequent construction.
Understanding Foundation Leveling
Leveling a foundation is crucial for the stability and longevity of any structure built upon it. An uneven foundation can lead to structural issues like cracked walls, uneven floors, and problems with doors and windows. When dealing with a sloped site for a concrete block foundation, specific techniques are employed to ensure the top course of blocks forms a perfectly level plane.
The Leveling Process on a Slope
One primary method for leveling a concrete block foundation on a site with a slope involves adjusting the height of the block courses, particularly on the lower side of the site.
As highlighted in Step 5: Level the Blocks: If your site has a slope and it is not possible to place blocks on the same level, stack solid-concrete blocks on the low end. Use 2-, 4-, or 8-inch-thick blocks to raise the low end of the site level with the high end.
This means:
- Identify the High and Low Points: Determine the highest and lowest points of the foundation area on the sloped site.
- Establish the Target Level: The target level is typically determined by the highest point. All other areas must be built up to this height.
- Build Up the Low Side: On the lower end of the site, you will stack extra courses of solid concrete blocks.
- Use Appropriate Block Thicknesses: To achieve the exact level needed, you can use different thicknesses of solid concrete blocks. The reference specifically mentions using 2-, 4-, or 8-inch-thick blocks as supplemental layers on the low side to meet the level established by the high end.
Practical Considerations
- Mortar Beds: Each course of blocks, including the leveling courses on the low end, is typically laid on a bed of mortar to ensure full bearing and bond.
- Using a Level: A builder's level, transit level, or laser level is essential throughout this process to accurately check and maintain the level of the top course of blocks across the entire foundation perimeter.
- Solid vs. Hollow Blocks: While standard foundation walls often use hollow blocks, solid blocks are frequently preferred for the initial leveling courses, especially when dealing with significant height differences, as they provide a dense, stable base.
Example Scenario
Imagine a foundation site with a 12-inch slope from one corner (high point) to the opposite (low point).
- The high side starts with a block course directly on the footing.
- The low side needs to be built up by 12 inches before the standard courses begin.
- This can be achieved by laying:
- Three 4-inch solid blocks stacked vertically, or
- One 8-inch block and one 4-inch block, or
- Other combinations using 2-, 4-, or 8-inch-thick blocks as needed to reach the 12-inch difference.
Once the low side is built up to the same level as the high side using these supplemental courses, subsequent courses of standard blocks are laid evenly around the entire foundation perimeter, maintaining the newly established level plane.
This method ensures that despite the sloped terrain, the critical top surface of the concrete block foundation is perfectly horizontal, providing a stable base for the rest of the structure.
