64. For the purposes of this Act the term “improvements” used with reference to a tenancy shall mean any work which adds to the value of the non-agricultural land comprised in the tenancy, which is suitable to such land and consistent with any of the purposes specified in section 4 for which it is being used and which, if not executed on such land, is either executed directly for its benefit, or is, after execution, made dibeneficial to it, and subject to the foregoing provisions, shall include the following, namely:-(a) laying out of passages or roads,(b) providing open spaces for ventilation,(c) providing facilities for taking water,(d) laying out drainage connections,but shall not include any work executed by a non-agricultural tenant if it substantially diminishes the value of his landlord's property.