P.R. Laws tit. 31, § 1757
Every owner may construct a party wall by erecting it at his own expense, and by paying for any damages which may be caused by the work, even when only temporary.
He shall also have to pay for the expenses of maintaining the wall in the part newly raised or deepened at its foundation, with regard to its former condition, and besides the indemnity for the increased expenses which it may be necessary to incur in order to preserve the party wall by reason of the greater height or depth which has been given the same.
If the party wall cannot resist the increased height, the owner desiring to raise it shall be obliged to reconstruct it at his own expense, and, should it be necessary therefor to make it thicker, he shall give the space required from his own land.
History —Civil Code, 1930, § 513.