How can I protect my foundation when removing old retaining walls and regrading?

Question

I have this old and crumbling tiered stone wall in the back of my property. My deck sits on top the wall. There is a covered porch next to the deck, that’s built on top of block walls (not part of the foundation or basement walls of house.

I want to tear down the stone wall, remove the dirt under the deck so I have space under there for my lawn equipment (and reclaim space in the garage).

Is there any potential issues with stability to the foundation of the house if I do this? My yard slopes away from the house, and I will ensure proper grade under the deck so rainwater continues to flow downhill.

Also I’m assuming the deck footings will need to be replaced once the dirt is gone, any tips for temporary supports for the deck while the dirt is being removed?

I plan to also remove the concrete blocking under the porch and replace with footings similar to the deck. Any recommendation on safely removing the blocks and supporting the porch in the process?

Answer 1

I would probably remove the deck first.

After the deck is disassembled, then start the excavation, it will be much easier and safer.

You might find out it is less work to remove the deck compared to trying to work under it with limited space and temporary supports. Temp supports sounds like a catastrophe waiting to happen.

Removing the block wall that is under the porch should be a totally different question as it is also involved because it carries the porch decking and the roof.

Answer 2

Let's address the safety issues first...

Working under your deck and porch obviously presents serious safety concerns. A wrong move here could be deadly. I'd follow these guidelines and good sense in general:

• Block access to the deck during all work. No one should be allowed on it.
• Work one footing (or maybe a few) at a time, relying on existing (and eventually replacement) posts for ongoing stability.
• Excavate around the footing to the new grade, then set up temporary posts. These should be on solid bases, which can simply be crosswise lumber, to prevent settling if it rains. Use multiple posts, with one on each side of the deck. Be sure to leave adequate space to dig the new footing in below grade. Posts should be equal to the task. Two 2x4 boards in a well-fastened T configuration are ok, for example. A single 2x4 is not adequately stiff. Posts should be screwed to the beam at the top to prevent accidental displacement.
• Once the deck is securely supported, remove and replace the original post and footing. Before cutting the post to length, evaluate the overall level of the deck and make any adjustments.

Then, about your foundation...

Barring any odd, unknown issues, your foundation does not depend on backfill for stability. It's stable with nothing around it. In fact, more problems occur during backfill and as the soil settles if it's not done properly.

However, your home may be taking advantage of the insulation and ground-source heat properties of the existing grade. Consider whether your energy walls are adequate to handle the new exposure to the elements lower on the wall.

I would advise you to work slowly and carefully and regularly check inside the foundation for signs of movement or other effects. Otherwise you should be fine.