How to Make an 8 Foot Concrete Foundation Into a 9 Foot

Foundation walls must be well-supported by wood frames while setting.

Pouring a concrete foundation is a major undertaking, and changing your mind about the shape or size of your basement after the fact can result in untold frustration. Raising the height of the walls, however, is a much simpler operation. To increase the height of your foundation walls from a standard 8 feet to 9 requires little more than setting up a wooden form and pouring the concrete in.

Things You'll Need

• Detergent
• Scrub brush
• 2-by-4 lumber
• Plywood sheets
• Portland cement
• Water
• Gravel
• Sand
• Trowel
• Plastic wrap

Instructions

1. Clean the upper surface of the foundation wall, first brushing away all debris and then scrubbing with a grease-cutting detergent.

2. Build a wooden frame against the wall on both sides, exceeding the original height by 1 foot. The exact steps to do this will vary depending on the shape of your foundation, but the frame should generally consist of plywood sheets braced by diagonal 2-by-4s on both sides.

3. Wait for a cloudy day with little wind and a temperature in the 50s or 60s, if possible. These weather conditions will contribute to getting the best results in laying the new concrete.

4. Mix Portland cement and water to a paint-like consistency and set it aside. Mix three parts gravel, two parts sand and one part Portland cement to create your concrete mix, adding water until it is thick but malleable.

5. Dampen the upper surface of the foundation wall and then paint it with a coat of cement paste to help the fresh concrete adhere to the old. Pour the concrete into the wooden form until even with the upper edge around the entire wall. Trowel the upper surface smooth after all visible water on top disappears and cover it with plastic wrap. Wait a week before removing the plastic and wood supports.

References

• Ask the Builder: Concrete Resurfacing
• The Family Handyman: How to Pour Concrete