*741OPINION
By the Court,
Steffen, J.:Appellants seek relief from the district court’s order mandating appellants’ approval of respondents’ application for architectural supervision and issuance of a building permit. We conclude that the district court erred in granting mandamus and therefore reverse.
Respondent CMC of Nevada, Inc. (CMC) is the owner of certain real property situated adjacent to the Desert Springs Hospital in Clark County, Nevada. On April 13, 1979, CMC applied for a C-P zoning change on the subject property for the purpose of constructing “parking lot facilities.” Thereafter, on June 5, 1979, appellant Clark County Board of Commissioners (Board) approved the requested zone change. Two months later, respondents applied to the Clark County Planning Commission (Commission) for a conditional use permit and variance to construct and maintain, within 5 feet of the side property line, an 80 bed psychiatric hospital on the property which had been previously zoned C-P. On October 2, 1979, the Board followed the recommendation of the Commission and approved the applications for a conditional use permit and variance. The variance was modified, however, so as to require a minimum setback of 15 feet from the side property line.
The public notice for the use permit and variance described the proposed facility merely as a hospital, not a psychiatric hospital.
Prior to obtaining a building permit, CMC applied for architectural supervision.1 The application was filed on October 20, 1980, in furtherance of the use permit and variance previously granted. On November 20, 1980, after public notice, the matter of architectural supervision came before the Commission in a *742public hearing.2 The hearing resulted in a refusal to approve CMC’s plans, assertedly due to an inadequate setback or “buffer” between the proposed project and an adjacent elementary school.3 The Board unanimously concurred with the action and recommendation of the Commission on January 20, 1981. As a result of the foregoing action, the Clark County building inspector refused to issue the building permit which was requisite to the commencement of construction of the psychiatric hospital.
On the assumption that the Board’s approval of the conditional use permit and variance would enable them to proceed, respondents expended in excess of $120,000 and entered into construction commitments of over $2,000,000 in furtherance of the proposed project.4
Respondents sought to break the impasse by filing suit and requesting mandamus to force County authorities to favorably act upon CMC’s application for architectural supervision and to require the County to issue a building permit. The district court held that the Commission’s discretion under the architectural supervision ordinance, Chapter 29.52 (Ordinance), was limited to considerations which were of an “aesthetic or appearance” nature and that the action of the Board and Commission in refusing to approve CMC’s plans was arbitrary, capricious and an abuse of discretion. The district court then ordered that a peremptory writ of mandate issue requiring the County to “grant” CMC’s application for architectural supervision and to issue a building permit.
Appellants claim entitlement to relief on the primarycontention that the lower court was unduly restrictive in its construction of the county ordinance respecting architectural *743supervision. We are asked to construe the language of the Ordinance to permit the imposition of non-aesthetic requirements, such as an enlarged buffer zone, thus entitling the Commission and the Board to impose substantive modifications to plans and specifications which are approved in the course of granting a zone change, use permit or variance.
The scope and effect of the Ordinance are threshold issues on appeal. If we were to accept the limited construction of the district court, respondents’ right to proceed with the project would be apparent. It is conceded that the Commission found no problems with the appearance of the planned facility. Thus, in undertaking architectural supervision, if the Commission’s function under the Ordinance is confined to project aesthetics, CMC should have received the necessary plan approval.
We do not agree with the district court’s conclusion. In our view, the Ordinance was not enacted to merely provide perfunctory review and endorsement of plans previously submitted in support of a conditional use permit request. First, we observe that the Commission may require architectural supervision in any given instance irrespective of the substantial conformity of the plans to those submitted and approved in connection with the granting of a conditional use permit. Section 29.52.010(c). This grant of discretion in the Commission is provided in order to promote the purposes of the zoning title in accordance with Section 29.01.020. The latter section specifies that the purpose of the title is to promote “the health, safety, morals or general welfare of the present and future inhabitants of Clark County. . . .” It further indicates, in part, that the title is designed “to ensure that the development of land is commensurate with the character and the physical limitations of the land”, “to take into account . . . the relative suitability of such land for such development” and “to promote health and the general welfare.” Further, the referenced general purpose section of title 29 reflects consideration in its enactment for “encouraging the most appropriate use of land throughout Clark County.”
The Commission could hardly function in effective promotion of the recited purposes of the zoning title if it were restricted solely to considerations of aesthetics. We must conclude that subsection (c) of the Ordinance validly recognizes authority and discretion in the Commission to require whatever measures are necessary to satisfy the concerns which prompted an imposition of architectural supervision.
Respondents nevertheless contend, and the district court agreed, that the following language of the Ordinance makes clear its narrow purview:
*744The planning commission shall consider these drawings, plans and sketches in an endeavor to provide that such buildings, structures and other improvements shall be designed and constructed so that they will not become unsightly, undesirable or obnoxious in appearance to the extent that they will hinder the orderly and harmonious development of the county, limit the opportunity to attain the optimum use and value of land and improvements, impair the desirability of living conditions in the same area or adjacent agricultural or residential areas, or otherwise adversely affect the general prosperity or welfare. (Emphasis supplied.)
It is argued, as held by the lower court, that the words “unsightly”, “undesirable” and “obnoxious” are all modified or defined by the prepositional phrase “in appearance”. Such a construction would supply redundancy to the word “unsightly”. It would likewise deprive the term “undesirable” of meaningful import since it would be merely repetitive of the term “unsightly”, and thus also redundant. The term “obnoxious”, however, invited modification since it may connote in general, an offensive, disgusting, reprehensible, harmful, odious or objectionable nature which, unless so modified, may potentially cast County action approving a conditional use permit in a position of obloquy. See Webster’s Third New International Dictionary.
Courts must construe statutes and ordinances to givé meaning to all of their parts and language. State ex rel. List v. AAA Auto Leasing, 93 Nev. 483, 568 P.2d 1230 (1977), Nevada State Personnel Division v. Hashins, 90 Nev. 425, 529 P.2d 795 (1974). The court should read each sentence, phrase, and word to render it meaningful within the context of the purpose of the legislation. See State Gen. Obligation Bond v. Koontz, 84 Nev. 130, 437 P.2d 72 (1968). A reading of legislation which would render any part thereof redundant or meaningless, where that part may be given a separate substantive interpretation, should be avoided.
Our review of the Ordinance in question reveals that the district court’s construction unnecessarily renders the word “undesirable” meaningless, at the expense of a reading which would render the language significant within the context of the stated policy of promotion of the public safety, health and welfare. We find such an interpretation unacceptable and hold that *745the prepositional phrase “in appearance” modifies only the term “obnoxious”.
The above construction of the Ordinance will subserve the purposes of its enactment, thereby allowing the Commission to provide meaningful assurance that the public health, safety and welfare will be promoted, and that land will be accorded its most appropriate use. Such a construction will also give effect to the unquoted part of the Ordinance quoted above:
To this end the planning Commission shall suggest any changes in the plans of such proposed buildings, structures and other improvements which it may deem necessary to accomplish the purposes of this chapter, and may refuse to approve any such plans until it is satisfied that such purposes will be accomplished thereby.
Our construction of the Ordinance is also supported by the amendment to the Ordinance enacted subsequent to the action in question.
When a former statute is amended, or a doubtful interpretation is rendered certain by subsequent legislation, the amendment is persuasive evidence of the purpose and intent of the legislature in passing the former (unamended) statute. See Woofter v. O’Donnell, 91 Nev. 756, 542 P.2d 1396 (1975); Sheriff v. Smith, 91 Nev. 729, 542 P.2d 440 (1975).
Here, the Ordinance was modified to read as follows:
The planning commission shall consider these drawings, plans and sketches in an endeavor to provide that the design of such buildings, structures and other improvements shall be adequate to prevent them or the uses for which they are to be utilized from being unsightly, undesirable or obnoxious to the extent that they will hinder the orderly and harmonious development of the county, limit the opportunity to attain the optimum use and value of land and improvements, impair the desirability of living conditions in the same area or adjacent areas, or otherwise adversely affect the general prosperity or welfare. To this end, the planning commission may require any changes in the plans of such proposed buildings, structures and other improvements which it deems necessary to accomplish the purposes of this chapter, and may refuse to approve any such plans until it is satisfied that such purposes will be accomplished thereby. As a prerequisite to approval of any application for architectural supervision, the planning commission may impose any condition, including but not *746limited to flood control, additional setbacks, off-site improvements, landscaping, street dedication, wall enclosures, noise circulation, that it deems necessary to accomplish the purposes of this chapter. (Emphasis added.)
The deletion of the words “in appearance” after the word “obnoxious” indicates that architectural supervision is intended to go beyond review of the merely aesthetic aspects of a project, and extends to evaluation of a project design within the context of public health, safety, and welfare considerations. That the amended Ordinance details conditions which may be imposed by the Commission prior to approval of an application for architectural supervision also supports our construction that the Ordinance provides substantive powers to the Commission at the architectural supervision stage.
We are equally unpersuaded by respondents’ characterization of “absurdity” to a statutory scheme which would ostensibly enable the Commission and Board to disapprove under architectural supervision a project which both bodies approved at the conditional use permit and variance hearings. First, we do not ascribe to the Ordinance a plenary function regarding project acceptability. It is one thing to impose conditions necessary to the satisfaction of title 29 purposes; it is quite another to rescind the prior final action of the Commission and Board granting life to the project.
We are not offended by the possibility of duplicative considerations. Architectural supervision may act as an added precaution or “failsafe” system to assure proper deference to the general welfare purposes of title 29. For example, at the hearings regarding the conditional use permit and variance, both the Commission and Board failed to focus on the special public concerns pertaining to the introduction of a psychiatric care facility in the immediate vicinity of an elementary school and residential neighborhood. The public within the noticed area of the intended project were apparently unaroused by the public notice concerning these hearings because it described the project only as a hospital. Since respondents also own the general care hospital, Desert Springs, situated adjacent to the proposed project, it is apparent that interested and affected members of the public incorrectly assumed that the Desert Springs general care hospital was simply being enlarged. When the project was fully described as a psychiatric hospital in the public notice pertaining to architectural supervision, many organizations and individuals appeared to voice their concerns. As a result, the Commission, sitting in its capacity under the Ordinance, was able to focus in substantial detail on matters pertaining to the *747purposes of title 29 and the Ordinance in relation to the pending project. The Commission, armed with further enlightenment and insight, was then in a position and indeed, under a duty, to exercise its discretion to assure that the project conformed, at least to the highest possible extent, with the purposes of title 29 and the Ordinance.
In view of our construction of the Ordinance, it is clear that the Commission’s function thereunder contemplates a substantial exercise of discretion. This, in turn, is dispositive of respondents’ attempt to sustain the district court’s conclusion of law that respondents enjoyed a vested right to construct and operate a psychiatric hospital. Although certain inroads are appearing in the general rule that vested rights against changes in the zoning laws exist only after the issuance of a building permit and the commencement of construction, such inroads do not confer vested rights unless zoning or use approvals are not subject to further governmental discretionary actions affecting project commencement. See Tosh v. California Coastal Commission, 99 Cal.App.3d 388, 160 Cal.Rptr. 170 (1979); South Central, etc. v. Charles A. Pratt Const., 128 Cal.App.3d 830, 180 Cal.Rptr. 555 (1982). See also Town of Paradise Valley v. Gulf Leisure Corporation, 557 P.2d 532 (Ariz. 1976); Gosselin v. City of Nashua, 321 A.2d 593 (N.H. 1974).
Since the Ordinance contemplates the exercise of substantial discretion by the Commission in the execution of its functions, it is apparent, and we so hold, that respondents do not have vested rights under any of the case authorities.5
Finally, the district court determined that county authorities acted arbitrarily, capriciously and in abuse of their discretion in refusing to approve respondents’ plans during the hearings on architectural supervision. On the record before us, we must agree.
The project plans submitted by respondents for approval *748during the hearing on architectural supervision were substantially identical to those approved when the conditional use permit was granted. Therefore, substantive modifications or changes imposed as a condition to project approval at the architectural supervision stage must have been supported by evidence and cogent reasons consonant with the purposes of the ordinance. It appears from the record that the requisite support is lacking.
The record suggests, as did counsel for appellants during oral argument, that the expanded setback requirement was arbitrarily imposed in order to kill the project. If so, such an imposition constituted a clear abuse of discretion by county authorities. As indicated previously, the Ordinance contemplates a governmental function beyond mere aesthetics but short of the ultimate authority to rescind prior approvals by the Commission and Board. An attempt to frustrate a project by imposing unsupported changes of a magnitude which would assure such a result is tantamount to a rescission of prior project approvals. We are not suggesting, however, that substantive changes may not be required at the architectural supervision stage. When such changes are imposed, they must be supported by evidence and cogent reasons.
Since evidence and cogent reasons were substantially absent in requiring a vastly expanded setback of undetermined dimension as opposed to the 15-foot setback approved with the conditional use permit, we have concluded that such a requirement was arbitrary and constituted an abuse of discretion.
Upon remand, if CMC desires to resubmit its application for architectural supervision, we will assume that the county will perform its function within the letter and spirit of the laws under which it must operate. This means that any substantive changes imposed by the county during the architectural supervision stage of CMC’s project must be supported as indicated above.
The district court issued a writ of mandamus essentially compelling the county to forego meaningful architectural supervision and to issue a building permit allowing CMC to proceed with the construction of the project under its present plans and specifications. This was error. Since respondents’ rights are not vested, and in view of the substantive purpose of the Ordinance, it is essential that county authorities be permitted to pursue their expected functions under the Ordinance.
Under the circumstances of this case, mandamus is not *749appropriate, and the writ must be vacated. See State ex rel. Lawton v. Public Service Commission, 44 Nev. 102, 190 P. 284 (1920). We remand the matter to the appropriate county authorities who, upon resubmission of an application for architectural supervision by respondents, are expected to entertain such application in accordance with this opinion.6
Other issues raised on appeal have been considered and deemed to be without merit in light of our disposition of this appeal.
The district court order granting the writ of mandamus is hereby reversed and the case remanded for proceedings consistent with this opinion.
Manoukian, C. J., and Mowbray J., concur.The parties concede the proposition that architectural supervision is required. In any event, the Commission or its designated representative may impose an architectural supervision requirement in order to promote the purposes of the zoning laws. 29.52.010(c).
The public notice given in connection with this hearing disclosed for the first time the fact that the proposed facility was a psychiatric hospital. The result was a solid storm of protest from various groups and residents who opposed construction of the hospital immediately adjacent to an elementary school and residential neighborhood. Although the County failed to disclose the psychiatric aspect of the facility in its public notice for a use permit and variance, the parties have concluded that adequacy of public notice is not an issue in this appeal.
Counsel for appellants conceded at oral argument that it may be fairly inferred from the record that the purpose for imposing an expanded setback on the project was to assure its demise.
Actually, the record reflects that CMC contractually reserved the right to rescind the $2,528,000 construction contract in the event it was unable to obtain proper zoning, a building permit or any other necessary governmental approval. In such event, CMC’s obligation to the contractor was not to exceed an amount covering reimbursement for actual expenses of performance under the contract plus 6 percent of those actual expenses. We were informed during oral argument that construction has not commenced on the project.
Although the vested rights doctrine is basically an application of equitable estoppel, it is commonly invoked as a means of avoiding changes in the zoning laws occurring after final approvals are granted or permits issued by a governmental body. Here, the district court concluded as a matter of law that respondents enjoyed a vested right to construct and operate the psychiatric hospital. The lower court’s conclusion was not applicable to a change in any of the zoning laws since no such changes were then asserted as a basis for requiring substantive modifications in the project. We are, nonetheless, approaching the issue of vested rights as if it were raised in the traditional sense. In any event, for the reasons stated, we have concluded that respondents do not have a vested rights status.
We do not intend, by this opinion, to convey any attitude or inference regarding the ultimate disposition of respondents’ project.