<PAGE>   1
                                                                    EXHIBIT 3.1A

                                                [STATE DEPARTMENT OF ASSESSMENTS
                                                          AND TAXATION
                                                       APPROVED FOR RECORD
                                                      6/18/96 AT 10:09 a.m.]


                            SPIEKER PROPERTIES, INC.

                             ARTICLES OF AMENDMENT

        SPIEKER PROPERTIES, INC., a Maryland corporation, having its principal
office in the City of Baltimore, Maryland (the "Corporation"), hereby certifies
to the Maryland State Department of Assessments and Taxation that:

        FIRST: The Charter of the Corporation is hereby amended as follows:

        1. Subparagraph (a)(9) of Article NINTH is amended to read in its
entirety as follows:

        Exception. The Board of Directors, upon receipt of a ruling from the
Internal Revenue Service or an opinion of counsel in each case to the effect
that the restrictions contained in subparagraph (a)(2)(C) and/or subparagraph
(a)(2)(D) will not be violated, may exempt (i) a Person from the Ownership
Limit if such Person is not an individual for purposes of Section 542(a)(2) of
the Code (as modified by Section 856(h) of the Code) or (ii) is an underwriter
which participates in a public offering of the Equity Stock for a period of 90
days following the purchase by such underwriter of the Equity Stock and the
Board of Directors obtains such representations and undertakings from such
Person as are reasonably necessary to ascertain that no individual's Beneficial
Ownership of Equity Stock will violate the Ownership Limit and such Person
agrees that any violation or attempted violation will result in such Equity
Stock being exchanged for Excess Stock in accordance with subparagraph (a)(3)
of this Article NINTH and provided that any exemption of a Person under clause
(i) of this subparagraph shall not allow the Person to exceed 13.0% of the
value of the outstanding Equity Stock of the Corporation.

        2. Subparagraph (b)(1) of Article NINTH is amended to read in its
entirety as follows:

        Ownership in Trust. Upon any purported Transfer that results in Excess
Stock pursuant to subparagraph (a)(3) of this Article NINTH, such Excess Stock
shall be deemed to have been transferred to the Corporation, as Trustee of a
Trust for the Exclusive benefit of such Beneficiary or Beneficiaries to whom an
interest in such Excess Stock may later be transferred pursuant to subparagraph
(b)(5). Shares of Excess Stock so held in trust shall be issued and outstanding
stock of the Corporation. The Purported Record Transferee shall have no rights
in such Excess Stock except the right to receive a price for its interest in
the shares of Equity Stock which were exchanged for Excess Stock. The Purported
Beneficial Transferee shall have no rights in such Excess Stock except as
provided in subparagraph (b)(5).

        3. Subparagraphs (b)(5)(A) and (b)(5)(B) of Article NINTH are amended
to read in their entirety as follows:

        Restrictions on Transfer; Designation of Beneficiary.

        (A) Excess Stock shall not be transferable. The Corporation may
designate a Beneficiary of an interest in the Trust (representing the number of
shares of Excess Stock held by the Trust attributable to a purported Transfer
that resulted in the Excess Stock), if the shares of Excess

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Stock held in Trust would not be Excess Stock in the hands of such Beneficiary.
The Purported Beneficial Transferee may receive a price for its interest in the
shares of Equity Stock which were exchanged for Excess Stock provided that the
Purported Beneficial Transferee does not receive a price that reflects a price
per share for such Equity Stock that exceeds (i) the price per share such
Purported Beneficial Transferee paid for the Equity Stock in the purported
Transfer that resulted in the Excess Stock, or (ii) if the Purported Beneficial
Transferee did not give value for such shares of Equity Stock (through a gift,
devise or otherwise), a price per share equal to the Market Price on the date
of the purported Transfer that resulted in the Excess Stock. Upon such transfer
of an interest in the Trust, the corresponding shares of Excess Stock in the
Trust shall be automatically exchanged for an equal number of shares of Equity
Stock, and such shares of Equity Stock shall be transferred of record to the
Beneficiary of the interest in the Trust designated by the Corporation as
described above if such Equity Stock would not be Excess Stock in the hands of
such Beneficiary.

        (B) Notwithstanding the foregoing, if a Purported Beneficial Transferee
receives a price for its interest in the shares of Equity Stock which were
exchanged for Excess Stock that exceeds the amounts allowable under
subparagraph (b)(5)(A) of this Article NINTH, such Purported Beneficial
Transferee shall pay, or cause to be paid, such excess to the Corporation, or,
at the Corporation's sole election, such excess shall be offset against any
future dividends or distributions payable to such Purported Beneficial
Transferee.

        4.  Subparagraph (b)(3) of Article NINTH is amended to read in its
entirety as follows:

        Rights upon Liquidation.  In the event of any voluntary or involuntary
liquidation, dissolution, or winding up of, or any distribution of the assets
of, the Corporation, the shares of Excess Stock shall not be entitled to share
in any portion of the assets of the Corporation. At such time as (i) the
Corporation has received the necessary stockholder approval with respect to a
voluntary liquidation or dissolution of the Corporation, or (ii) the
Corporation has become the subject of an order of a court of competent
jurisdiction compelling an involuntary liquidation or dissolution of the
Corporation, such shares of Excess Stock held in Trust shall without further
act be extinguished and each Purported Beneficial Transferee whose acquisition
of Equity Stock resulted in the Excess Stock which has been extinguished
pursuant to this subparagraph (b)(3) of this Article NINTH shall without
further act become a creditor of the Corporation. The amount by which each such
Purported Beneficial Transferee shall become a creditor of the Corporation with
respect to its now-extinguished interest in the Trust (representing the number
of shares of Excess Stock held by the Trust attributable to a purported
Transfer that resulted in the Excess Stock) will be equal to the lesser of (a)
that amount of the distributable assets of the Corporation to which such Excess
Stock would be entitled if such Excess Stock were entitled to share ratably in
the distributable assets of the Corporation as shares of Common Stock, or (b)
as appropriate, either (1) the price per share paid by such Purported
Beneficial Transferee for the shares of Equity Stock which were exchanged for
Excess Stock, or (2) if the Purported Beneficial Transferee did not given value
for such shares of Equity Stock (having received such through a gift, device or
otherwise), a price per share equal to the Market Price on the date of the
purported Transfer that resulted in the Excess Stock. Payment to the Purported
Beneficial Transferee shall be without interest and shall be due concurrently
with the date of first distribution of liquidation proceeds to the holders of
Equity Stock. If the Corporation causes such liquidation or dissolution to be
revoked or otherwise rescinded any Excess Stock previously automatically
extinguished pursuant to this subparagraph (b)(3) of this Article NINTH


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shall be automatically revived and any Purported Beneficial Transferees shall
without further act cease to be creditors of the Corporation as otherwise
provided above.

        SECOND. The foregoing amendments to the Charter of the Corporation have
been approved by the shareholders of the Corporation at the Annual Meeting held
on May 22, 1996.

        IN WITNESS WHEREOF, SPIEKER PROPERTIES, INC. has caused these present
to be signed in its name and on its behalf by its Chairman of the Board and
Chief Executive Officer and witnessed by its Chief Financial Officer and
Executive Vice President on June 17, 1996.


ATTEST:                                 SPIEKER PROPERTIES, INC.
/s/ Craig G. Vought                     /s/ Warren E. Spieker, Jr.
-----------------------------           -----------------------------
Craig G. Vought                         Warren E. Spieker, Jr.
Chief Financial Officer and             Chairman of the Board and
Executive Vice President                Chief Executive Officer

        THE UNDERSIGNED, Chairman of the Board and Chief Executive Officer of
SPIEKER PROPERTIES, INC., who executed on behalf of the Corporation the
Articles of Amendment of which this certificate is made a part, hereby
acknowledges in the name and on behalf of said Corporation the foregoing
Articles of Amendment to be the corporate act of said Corporation and hereby
certifies that the matters and facts set forth herein with respect to the
authorization and approval thereof are true in all material respects under the
penalties of perjury.


                                        /s/ Warren E. Spieker, Jr.
                                        -----------------------------
                                        Warren E. Spieker, Jr.



                                       3
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                                                                   [SEAL]

                           SPIEKER, PROPERTIES, INC.

                             ARTICLES SUPPLEMENTARY

        SPIEKER PROPERTIES, INC., a Maryland corporation, having its principal
office in Baltimore City, Maryland (the "Corporation"), hereby certifies to the
State Department of Assessments and Taxation of Maryland that:

        FIRST:  Pursuant to a power contained in Article SIXTH, Section (d) of
the charter of the Corporation (the "Charter"), the Board of Directors of the
Corporation (the "Board of Directors"), has duly reclassified 1,500,000 shares
of the Common Stock (par value $.0001 per share) of the Corporation into
1,500,000 shares of a class designated as Class C Common Stock (par value
$.0001 per share) of the Corporation (the "Class C Common Stock"), and has
provided for the issuance of such shares.

        SECOND: Subject in all cases to the provisions of Article NINTH of the
Charter with respect to Excess Stock, the following is a description of the
preferences, conversion and other rights, voting powers, restrictions,
limitations as to dividends, qualifications and terms and conditions of
redemption of the Class C Common stock of the Corporation:

        1.  DESIGNATION AND AMOUNT.  The designation of the Class C Common
Stock described in Article FIRST hereof shall be "Class C Common Stock (par
value $.0001 per share)." The number of shares of the Class C Common Stock to
be authorized shall be 1,500,000.

        2.  DIVIDEND AND DISTRIBUTION PROVISIONS.

            (a)  Subject to the rights of series of Preferred Stock, now in
existence or which may from time to time come into existence, the holders of
shares of Class C Common Stock shall be entitled to receive dividends, when, as
and if authorized by the Board of Directors, out of any assets legally
available therefor, pari passu with any dividend (payable other than in Common
Stock of the Corporation) on Class B Common Stock and Common Stock of the
Corporation, in the amount per share of the Class C Dividend Amount, as in
effect from time to time. The initial per share Class C Dividend Amount per
annum shall be $1.73. In the event of any change in the per share dividend
amount (expressed in dollars) applicable to the Common Stock after the date of
filing of these Articles Supplementary, the Class C Dividend Amount shall be
adjusted by an equal dollar amount.

          (b)  In the event the Board of Directors shall authorize a
distribution payable in (i) securities of other persons, (ii) evidences of
indebtedness issued by the Corporation or other persons, assets (excluding cash
dividends) or (iii) options or rights to purchase stock or evidences of
indebtedness in the Corporation or other persons, then, in each such case for
the purpose of this subsection 2(b), the holders of the Class C Common Stock
shall be entitled to a

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                                     [SEAL]

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proportionate share of any such distribution as though they were the holders of
the number of shares of Common Stock of the Corporation into which their shares
of Class C Common Stock are convertible as of the record date fixed for the
determination of the holders of Common Stock of the Corporation entitled to
receive such distribution.

        3.      LIQUIDATION PAYMENTS.

                (a)     Subject to any prior rights of any other class or
series of stock, in the event of any liquidation, dissolution, or winding up of
the Corporation, either voluntary or involuntary, the holders of Class C Common
Stock shall be entitled to receive, pari passu with the holders of the Class B
Common Stock, and prior and in preference to any distribution of any of the
assets or surplus funds of the Corporation to the holders of Common Stock by
reason of their ownership of such stock, an amount per share of Class C Common
Stock equal to all declared but unpaid dividends for each share of Class C
Common Stock then held by them. If upon the occurrence of such event, the
assets and funds thus distributed among the holders of the Class C Common Stock
shall be insufficient to permit the payment to such holders of the full
aforesaid preferential amounts, then the entire assets and funds of the
Corporation legally available for distribution shall be distributed ratably
among the holders of the Class C Common Stock in proportion to the aggregate
preferential amounts owned to each such holder.

                (b)     Subject to any prior rights of any other class or
series of stock, after the payment or setting apart of payment to the holders
of Class C Common Stock of the full preferential amounts to which they shall be
entitled pursuant to paragraph 3(a) above, the holders of Class C Common Stock,
shall be entitled to receive the remaining assets of the Corporation ratably on
a per share basis (based on the number of shares of Common Stock held or Common
Stock issuable upon conversion of the Class C Common Stock held).

                (c)     A consolidation or merger of the Corporation with or
into any other corporation or corporations, or a sale, conveyance or
disposition of all or substantially all of the assets of the Corporation or the
effectuation by the Corporation of a transaction or series of related
transactions in which more than 50% of the voting power of the Corporation is
disposed of, shall not be deemed to be a liquidation, dissolution or winding up
within the meaning of this Section 3.

                (d)     In determining whether a distribution (other than upon
voluntary or involuntary liquidation), by dividend, redemption or other
acquisition of shares or otherwise, is permitted under the Maryland General
Corporation Law, amounts that would be needed, if the Corporation were to be
dissolved at the time of the distribution, to satisfy the preferential rights
upon dissolution of holders of Class B Common Stock, Class C Common Stock or
Preferred Stock whose preferential rights upon dissolution are superior to
those receiving the distribution shall not be added to the Corporation's total
liabilities.

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        4.      CONVERSION.  The holders of the Class C Common Stock shall have
conversion rights as follows (the "Conversion Rights"):

                (a)     RIGHT TO CONVERT.

                        (i)     Subject to subsections 4(a)(ii) and 4(c), on or
after the date three years after the closing of the initial issuance of Class C
Common Stock, each share of Class C Common Stock shall be convertible, at the
option of the holder thereof, at the office of the Corporation or any transfer
agent for the Class C Common Stock, into one fully paid and nonassessable share
of Common Stock (the "Conversion Ratio"). The Conversion Ratio for the Class C
Common Stock shall be subject to adjustment as set forth in subsection 4(d).

                        (ii)    Subject to subsection 4(c), each holder shall
have the right and option to convert all or a portion of its shares of Class C
Common Stock held into Common Stock before the date specified in subsection
4(a)(i) immediately after any of the following events:

                                (A)     The Corporation's management does not
include at least any two of John K. French, Warren E. Spieker, Jr., Dennis E.
Singleton and Craig G. Vought;

                                (B)     For any two consecutive quarters, the
Corporation's outstanding mortgage and other senior unsecured indebtedness is
greater than 65% of the Corporation's revenue less real estate taxes and rental
expenses (all as reported in the Corporation's Form 10Qs filed with the
Securities and Exchange Commission) for such two quarters, multiplied by two
and divided by nine percent; or

                                (C)     If (a) the Corporation shall be party
to, or shall have executed a definitive agreement for, any transaction
(including, without limitation, a merger, consolidation, statutory share
exchange or sale of all or substantially all of its assets (each of the
foregoing a "Transaction")), in each case as a result of which all or
substantially all shares of Common Stock shall have been or will be converted
into the right to receive stock, securities or other property (including cash
or any combination thereof) of an unrelated entity or which has resulted or
will result in the holders of the Corporation's outstanding voting securities
(including the Common Stock and the Series A Preferred Stock) immediately prior
to the Transaction owning less than 50% of the Corporation's outstanding voting
securities (including the Common Stock and the Series A Preferred Stock) after
the Transaction, or (b) a "change of control" as defined in the next sentence
occurs with respect to the Corporation. A change of control shall mean the
acquisition (including by virtue of a merger, share exchange or other business
combination) by one stockholder or a group of stockholders acting in concert of
the power to elect a majority of the Corporation's board of directors. The
Corporation shall notify the holders of Class C Common Stock promptly if any of
the events listed in this Section 4(a)(ii) shall occur.


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        (b)  MECHANICS OF CONVERSION.  Before any holder of Class C Common
Stock shall be entitled to convert such shares into shares of Common Stock, he
shall surrender the certificate or certificates therefor, duly endorsed, at the
office of the Corporation or of any transfer agent for the Class C Common Stock,
and shall give written notice by mail, postage prepaid, to the Corporation at
its principal corporate office, of the election to convert such shares and shall
state therein the name or names in which the certificate or certificates for
shares of Common Stock are to be issued. The Corporation shall, as soon as
practicable thereafter, issue and deliver at such office to such holder of
Class C Common Stock, or to the nominee or nominees of such holder, a
certificate or certificates for the number of shares of Common Stock to which
such holder shall be entitled as aforesaid. Such conversion shall be deemed to
have been made immediately prior to the close of business on the date of such
surrender of the shares of Class C Common Stock to be converted, and the person
or persons entitled to receive the shares of Common Stock issuable upon such
conversion shall be treated for all purposes as the record holder or holders of
such shares of Common Stock as of such date.

        (c)  LIMITATION ON NUMBER OF SHARES CONVERTED.  Each underlying holder
of a pecuniary interest in Class C Common Stock (a "Pecuniary Owner") shall be
limited in its right to convert shares of Class C Common Stock into Common
Stock as follows. At any time that a Pecuniary Owner holds 3.0% or more of the
Corporation's issued and outstanding Common Stock, such Pecuniary Owner at such
time shall not be entitled to convert any shares of Class C Common Stock. At
any time that a Pecuniary Owner holds less than 3.0% of the Corporation's issued
and outstanding Common Stock, such Pecuniary Owner shall at that time be
entitled to convert only up to such number of shares such that, immediately
after such conversion, such Pecuniary Owner will hold 3.0% of the Corporation's
issued and outstanding Common Stock. Any conversion in excess of the foregoing
limits or otherwise in violation of this subsection 4(c) shall to that extent be
void ab initio. If, for any reason, the foregoing sentence shall be
unenforceable at any time or with respect to any conversion, then any stock
converted in excess of the foregoing limits or otherwise in violation of this
subsection 4(c) shall be deemed and shall become Excess Stock, subject to all of
the rights, requirements and restrictions related thereto.

        (d)  CONVERSION RATIO ADJUSTMENTS OF CLASS C COMMON STOCK.  The
Conversion Ratio of the Class C Common Stock shall be subject to adjustment
from time to time as follows:

            (i)   In the event the Corporation should at any time or from
time to time after the initial date of issuance of shares of Class C Common
Stock (the "Purchase Date") fix a record date for the effectuation of a split
or subdivision of the outstanding shares of Common Stock or the determination
of holders of Common Stock entitled to receive a dividend or other distribution
payable in additional shares of Common Stock or other securities or rights
convertible into, or entitling the holder thereof to receive directly or
indirectly, additional shares of Common Stock (hereinafter referred to as
"Common Stock Equivalents") without payment of any consideration by such
holder for the additional shares of Common Stock or the Common

                                      -4-
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Stock Equivalents (including the additional shares of Common Stock issuable upon
conversion or exercise thereof), then, as of such record date (or the date of
such dividend distribution, split or subdivision if no record date is fixed),
the Conversion Ratio of the Class C Common Stock shall be appropriately
increased so that the number of shares of Common Stock issuable on conversion of
each share of such series shall be increased in proportion to such increase of
the aggregate of shares of Common Stock outstanding and those issuable with
respect to such Common Stock Equivalents.

                (ii) If the number of shares of Common Stock outstanding at any
time after the Purchase Date is decreased by a combination of the outstanding
shares of Common Stock, then, following the record date of such combination,
the Conversion Ratio for the Class C Common Stock shall be appropriately
decreased so that the number of shares of Common Stock issuable on conversion
of each share of such series shall be decreased in proportion to such decrease
in outstanding shares.

        (e) RECAPITALIZATIONS. If at any time or from time to time there shall
be a recapitalization of the Common Stock (other than a subdivision, combination
or other transaction provided for elsewhere in this Section 4), provision shall
be made so that each holder of the Class C Common Stock shall thereafter be
entitled to receive upon conversion of the Class C Common Stock the number of
shares of stock or other securities or property of the Corporation or otherwise,
to which such holder of Class C Common Stock would have been entitled on such
recapitalization had the holder of Class C Common Stock converted his shares
into Common Stock immediately prior to the record date set for holders of Common
Stock to participate in the recapitalization. In any such case, appropriate
adjustment shall be made in the application of the provisions of this Section 4
with respect to the rights of the holders of the Class C Common Stock, after the
recapitalization to the end that the provisions of this Section 4 (including
adjustment of the Conversion Ratio then in effect and the number of shares
issuable upon conversion of the Class C Common Stock) shall be applicable after
that event as nearly equivalent as may be practicable.

        (f) NO IMPAIRMENT. The Corporation will not, by amendment of the Charter
or through any reorganization, recapitalization, transfer of assets,
consolidation, merger, dissolution, issue or sale of securities or any other
voluntary action, avoid or seek to avoid the observance or performance of any of
the terms to be observed or performed hereunder by the Corporation, but will at
all times in good faith assist in the carrying out of all the provisions of this
Section 4 and in the taking of all such action as may be necessary or
appropriate in order to protect the Conversion Rights of the holders of the
Class C Common Stock against impairment.

        (g) NO FRACTIONAL SHARES AND CERTIFICATE AS TO ADJUSTMENTS. No
fractional shares shall be issued upon conversion of the Class C Common Stock,
and the number of shares of Common Stock to be issued shall be rounded to the
nearest whole share. Whether or not fractional shares are issuable upon such
conversion shall be determined on the basis of the total




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<PAGE>   9
number of shares of Class C Common Stock the holder is at the time converting
into Common Stock and the number of shares of Common Stock issuable upon such
aggregate conversion.

        (h)     SHAREHOLDER COMMUNICATIONS.     Holders of Class C Common Stock
shall be entitled to receive copies of all communications by the Corporation to
its holders of Common Stock, concurrently with the distribution to such
shareholders.


        (i)     RESERVATION OF STOCK ISSUABLE UPON CONVERSION.  The Corporation
shall at all times reserve and keep available out of its authorized but
unissued shares of Common Stock solely for the purpose of effecting the
conversion of the shares of the Class C Common Stock such number of its shares
of Common Stock as shall from time to time be sufficient to effect the
conversion of all outstanding shares of the Class C Common Stock; and if, at
any time, the number of authorized but unissued shares of Common Stock shall
not be sufficient to effect the conversion of all then outstanding shares of
the Class C Common Stock, in addition to such other remedies as shall be
available to the holder of such Class C Common Stock, the Corporation will take
such corporate action as may, in the opinion of its counsel, be necessary to
increase its authorized but unissued shares of Common Stock to such number of
shares as shall be sufficient for such purposes.

        (j)     NOTICES.        Any notice required by the provisions of this
Section 4 to be given to the holders of shares of Class C Common Stock shall be
deemed given if sent by overnight courier service and addressed to each holder
of record at his address appearing on the books of the Corporation.

        5.      NO VOTING RIGHTS.       The holders of shares of Class C Common
Stock shall have no right to vote with respect to any question upon which
holders of any other class of the Corporation's stock have the right to vote, or
on any other matters.

        6.      STATUS OF CONVERTED STOCK.      In the event any shares of Class
C Common Stock shall be converted pursuant to Section 4 hereof, the shares of
Class C Common Stock so converted shall revert to the status of authorized but
unissued shares available for future issuance and reclassification by the
Corporation.

        THIRD: These Articles Supplementary have been approved by the Board of
Directors in the manner and by the vote required by law.

        FOURTH: The undersigned acknowledges these Articles Supplementary to be
the act of the Corporation and states as to all matters and facts required to
be verified under oath, that, to the best of his knowledge, information and
belief, these matters and facts are true in all material respects and such
statement is made under penalties for perjury.


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<PAGE>   10
        IN WITNESS WHEREOF, SPIEKER PROPERTIES, INC. has caused these presents
to be signed in its name and on its behalf by its President and witnessed by
its Secretary on February 26, 1996.

WITNESS:                                    SPIEKER PROPERTIES, INC.

/s/ Adrian J. Gordon                        By: /s/ Warren E. Spieker, Jr.
----------------------------                    ---------------------------
Adrian J. Gordon                                Warren E. Spieker, Jr.
Secretary                                       President



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