<PAGE>   1


                                                                   EXHIBIT 24.0

                              POWER OF ATTORNEY


     KNOW ALL MEN BY THESE PRESENTS, that each of the undersigned hereby
constitutes and appoints Richard O. Ballentine and John Huey, and each of them,
his true and lawful attorneys-in-fact and agents, with full power of
substitution and revocation in each, for him/her and in his/her name, place and
stead, to sign any or all reports (including reports on Form 10-K, Form 3, Form
4, Form 5, Schedule 13-D, Schedule 13-G, and Form 144), and any amendments
thereto, required or permitted to be filed by him under the Securities and
Exchange Act of 1934, or the Securities Act of 1933, with respect to beneficial
ownership of, and transactions in, equity securities of BUTLER MANUFACTURING
COMPANY, a Delaware corporation (the "Company"), and with respect to other
matters relating to the Company, and to file the same, with all documents
required or permitted to be filed in connection therewith, with the Securities
and Exchange Commission, granting unto said attorneys-in-fact and agents, and
each of them, full power and authority to do and perform each and every act and
thing requisite and necessary to be done in and about the premises as fully to
all intents and purposes as he might or could do in person, hereby ratifying
and confirming all that said attorneys-in-fact and agents, or any of them, or
their substitute or substitutes, may lawfully do or cause to be done by virtue
hereof.

DATED: March 20, 1998                   /s/ HAROLD G. BERNTHAL
                                        ---------------------------------------
                                            HAROLD G. BERNTHAL

DATED: March 20, 1998                   /s/ ROBERT E. COOK
                                        ---------------------------------------
                                            ROBERT E. COOK

DATED: March 20, 1998                   /s/ ALAN M. HALLENE
                                        ---------------------------------------
                                            ALAN M. HALLENE

DATED: March 20, 1998                   /s/ C.L. WILLIAM HAW
                                        ---------------------------------------
                                            C.L. WILLIAM HAW

DATED: March 20, 1998                   /s/ ROBERT J. NOVELLO
                                        ---------------------------------------
                                            ROBERT J. NOVELLO

DATED: March 20, 1998                   /s/ GEORGE E. POWELL, JR.
                                        ---------------------------------------
                                            GEORGE E. POWELL, JR.

DATED: March 20, 1998                   /s/ DONALD H. PRATT.
                                        ---------------------------------------
                                            DONALD H. PRATT

DATED: March 20, 1998                   /s/ ROBERT J. REINTJES, SR.
                                        ---------------------------------------
                                            ROBERT J. REINTJES, SR.

DATED: March 20, 1998                   /s/ JUDITH A. ROGALA
                                        ---------------------------------------
                                            JUDITH A. ROGALA

DATED: March 20, 1998                   /s/ Gary L. Tapella
                                        ---------------------------------------
                                            Gary L. Tapella

DATED: March 20, 1998                   /s/ ROBERT H. WEST
                                        ---------------------------------------
                                            ROBERT H. WEST