Is foundation repair to a rented property considered land improvement or real estate asset?

I own a duplex (both sides) and rent both sides. I had to do foundation repairs on both sides.  Since the quote was a total without splitting costs by side, I used a factor based on the # of piers to each side to determine how much for each side.  Is this ok? Also, I am assuming this is an improvement.  When asked if  The cost of all repairs, maintenance and improvements is less than or equal to the smallest of these limits: 2% of the unadjusted basis of your building or $10,000, I answer NO.  After this is when I get stuck as I am not sure if foundation repair is considered land improvment or real estate? Please help? THanks.