Excellence in contracting is achieved by contractors who pay attention to all details; including the unglamorous ones that no one else pays attention to, like backfilling.
Backfilling, if done improperly can lead to problems like basement wall cracks and water leakage which can start during construction and continue long after it is complete.
There are four basics to proper backfilling:
- Protecting the foundation from damage during backfilling
- Placing proper backfill material
- Compacting the backfill material
- Grading to slope water runoff away from the house
The best way to protect the foundation wall from the pressures and potential damage caused by backfilling is to begin after the basement floor slab and first floor deck are in place. The slab and deck will support the walls against the inward pressure created by the backfill material being placed. An alternative to this is to brace the walls once they have reached proper strength. Bracing the walls allows for early backfill and easier accessibility to the house for carpenters to begin framing. Applicable bracing design and local codes apply.
Proper backfill material that restores the equilibrium of the moisture system is the goal. Design drawings, engineering standards and local codes are to be followed and heavy, moisture laden and expansive materials should be avoided.
Proper backfill material that is placed in thin sections of 6” lifts and vibrated or compacted in place will minimize future settlement, which leads to drainage problems. Larger sections of say 24” when compacted from the top can appear satisfactory on the surface, but only the first 8”may be adequately compacted. Compacting in thin sections by qualified operators takes more time, but is time well spent.
Sloping the grade away from the house per local building code combined with downspout splash blocks are one of the most effective means of avoiding basement water issues by diverting water away from the house.
Properly supervised and correct backfilling maintains the integrity of a residential foundation and together with a proper drainage system works to keep the basement dry long after construction is complete.
Reference: Bartley, R.T.B. (1991). Backfilling Basics: Backfilling the wrong way often costs more than doing it right. The Aberdeen Group
Emil Turean, Principal, Crown Construction
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