Civil Code (Cap. 16), article 414

414. Every co-owner may raise the height of a common wall, but he shall be liable fo r the expenses necessary - (a) for raising the height of the wall; (b) for keeping in good repair the part raised above the height of the common wall; (c) for carrying out such works as may be necessary for the support of the additional weight resulting from the raising of the wall, so that the stability of the wall will not be impaired. Where common wall is not in condition to stand additional height.