ROWHOUSE Basement lowering - Contractor OVEREXCAVATED 3

[Ben29]

I am working with a contractor who never performed basement lowering (basement underpinning). I agreed to provide underpinning sequence drawings. I get to the house to take measurements so that I can create the drawings. I get there and find out that they totally excavated the entire basement, 15 inches below the existing foundation walls!!! I told them to stop digging immediately. But the entire basement is now dug out. I am sending them temporary bracing details to keep the end walls from caving in (rowhouse is an end-unit next to an alley = vehicle surcharge on endwall!).

aside from the bracing detail, what do I do to temporary support the walls from below? good chance we won't start underpinning for a couple of weeks yet. or Do we just start underpinning as this has now become an emergency repair?

 

[Ben29]

The temporary bracing was done yesterday. I contacted the permit office today and told them the situation. I told them that they need to close the alley to vehicular traffic. (I don't know who is the right person to call to request a road closure?) The permit office told me to submit the underpinning drawings today and they will expediate review. I told the contractor to bring in the stone and berm it per PEinc's suggestion in the meantime.

 

[phamENG]

Nice. I'd throw some sandbags at least on the base of your braces. Looks like they could kick up if they really wanted to.

 

[BAretired]

If underpinning is to be performed, it will need to be performed in stages, but no matter how careful the contractor is, the soil will be compromised even more than it is now until after the concrete cures and the walls are bearing on something a little more robust.

It is likely going to be a while before the work is completed. In the meantime, the floor(s) and roof above, should be temporarily shored for the protection of the workers. That will add substantially to the cost of the work, but I don't believe it can safely be avoided.

BA