Properly Backfilling Foundation Reduces Structural Foundation Damage Risks and Ensures a Drier Basement
By Mark J. Donovan
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So you’re having a new home built and the foundation walls have recently been poured on top of the concrete footings. Two questions that often come up after the foundations walls have been poured is (1) how to backfill a foundation wall correctly, and (2) when should it be done.
When to Backfill Foundation Walls The second question is easiest to address. A foundation wall should ideally sit for about a month before it is backfilled to allow the concrete in the foundation walls to fully cure. |
By waiting this length of time there is less risk that the foundation walls will crack, or even worse, collapse when backfilling the foundation walls.
In addition, it is best to hold off backfilling a foundation wall until the concrete basement slab floor is poured. The basement slab floor also helps to add rigidity to the foundation walls and helps to mitigate the risks of damage to the foundation walls during the backfilling process.
Lastly, it is best to have the framers install the first-floor deck to the foundation walls for effectively bracing the top of the foundation walls. By installing the first-floor deck surface they again help mitigate the risk of the foundation walls cracking or caving in during the foundation backfilling process.
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Often general contractors don’t want to wait the month for the foundation walls to cure, because time and inconvenience is money. Not backfilling the foundation walls can delay the framing process to begin, or make it a more dangerous and inconvenient work environment for the framing crew as they can’t as easily access the foundation walls to begin installing the first-floor deck. How to Backfill a Foundation Wall Prior to backfilling a foundation wall, a perimeter drain system should be placed around the foundation wall. |
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In addition, the foundation walls should be waterproofed sealed to mitigate the risk of water seepage into the basement.
Lastly, rigid foam insulation, or some equivalent type of insulation process, should be done in the exterior foundation walls.
In regards to the actual foundation backfilling process, it should be done in steps. Meaning, after every couple of feet of material that has been backfilled around the foundation walls it should be compacted. This process should be repeated until the grade of the soil has been brought up to the desired height around the foundation walls, e.g. 12 to 24 inches.
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Best Foundation Backfill Soil Material Type Ideally the same soil that was taken out of the ground around the foundation walls should be used to backfill around them. Unless, however, the soil was expansive clay or heavy moisture laden material. If this is the case, then granular fill material should be used, as this type of fill material will compact nicely and allow proper water drainage from the foundation walls. Also, make sure to not use fill that has roots and other types of organic matter. |
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Ensure a Proper grade when Backfilling Foundation Walls
When finishing off the backfilling of a foundation make sure that a gentle grade away from the foundation walls is created. This will help to direct water run-off from the house’s roof to drain away from the foundation walls.
Putting In Rain Gutters and Downspouts
After the house been completed rain gutters and downspouts should be installed on the roof eaves to minimize erosion of the backfill soil around the foundation.
By following all of these “how-to backfill a foundation” tips you will dramatically reduce the risk of creating foundation cracks during the backfilling of it and having future water problems in your basement.
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