(1)

If any building which abuts on a public street is in rear of the regular line of such street the Commissioner may, whenever it is proposed-

(a) to rebuild such building, or

(b) to alter or repair such building in any manner that will involve the removal or re-erection of such building, or of the portion thereof which abuts on the said street, to an extent exceeding one-half of such building or portion thereof above the ground level, such half to be measured in cubic feet,

(2)

For the purposes of this section, a wall separating any premises from a public street shall be deemed to be a building; and it shall be deemed to be a sufficient compliance with a permission or requisition to set forward a building to the regular line of a street if a wall of such materials and dimensions as are approved by the Commissioner is erected along the said line.