No contract for the construction of any building or for an addition to or improvement of an existing building by any local governing body or subdivision thereof for which state funds of not more than $50,000 in the aggregate or for the sum of all phases of a contract or project either by appropriation, grant-in-aid or loan, are used or are to be used for all or part of the cost of construction shall be let except after competitive sealed bidding or after competitive negotiation as provided under subsection D of § 2.2-4303 or Chapter 43.1 (§ 2.2-4378 et seq.). The procedure for the advertising for bids or for proposals and for letting of the contract shall conform, mutatis mutandis, to this chapter.