Except as otherwise provided in this chapter, any use existing in any building or premises at the time of taking effect of this chapter and not conforming with the provisions hereof with regard to the use of the district in which it is maintained may be continued therein, provided that such building or premises shall not be enlarged or extended or be reconstructed or altered to any extent greater than 50% of the value of the building, unless such use is changed to a use permitted in such district for a new building.

Except as otherwise provided in this chapter, in any district any building erected or used for dwelling purposes shall be subject to the same restrictions as to type, use, area, size of plot, side line and setback requirements as specified for a one-family dwelling under the Residence A District of this chapter.