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                                                                    EXHIBIT 10.7

                               LAFARGE CORPORATION

                          OPTIONAL STOCK DIVIDEND PLAN

                                 SEPTEMBER 1999

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                                TABLE OF CONTENTS

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PRINCIPAL FEATURES AND BENEFITS..................................................   1

THE PLAN - DESCRIPTION, TERMS AND CONDITIONS.....................................   4

        ELIGIBLE SHARES..........................................................   4
        PARTICIPATION............................................................   4
        ELIGIBLE STOCKHOLDERS....................................................   4
        ENROLLMENT...............................................................   5
        VALUATION AND PRICE OF ADDITIONAL SHARES OF COMMON STOCK.................   6
        CERTIFICATES FOR ADDITIONAL SHARES OF COMMON STOCK.......................   6
        STATEMENTS OF ACCOUNT....................................................   7
        TERMINATION OF PARTICIPATION.............................................   8
        STOCKHOLDER VOTING.......................................................   9
        RIGHTS OFFERINGS, STOCK SPLITS AND STOCK DIVIDENDS.......................   9
        RESPONSIBILITIES OF THE CORPORATION AND THE PLAN AGENT...................  10
        RISK OF MARKET PRICE FLUCTUATIONS........................................  10
        AMENDMENT, MODIFICATION, SUSPENSION OR TERMINATION
               OF THE PLAN.......................................................  10
        NOTICES..................................................................  10
        ADMINISTRATION FEES......................................................  11
        APPLICATION OF FUNDS.....................................................  11
        PRINCIPAL STOCKHOLDER....................................................  11
        EFFECTIVE DATE...........................................................  11

TAX CONSIDERATION................................................................  11

        U.S. FEDERAL INCOME TAX CONSIDERATIONS...................................  12
        CANADIAN INCOME TAX CONSIDERATIONS.......................................  13
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THIS CIRCULAR DESCRIBES THE OPTION AVAILABLE TO HOLDERS OF SHARES OF COMMON
STOCK, PAR VALUE $1.00 PER SHARE ("COMMON STOCK"), OF LAFARGE CORPORATION (THE
"CORPORATION") OR OF SHARES OF ANY OTHER CLASS OR SERIES OF STOCK OF THE
CORPORATION DESIGNATED BY THE BOARD OF DIRECTORS, TO RECEIVE PAYMENT OF THEIR
DIVIDENDS ON SUCH SHARES IN THE FORM OF NEW SHARES OF COMMON STOCK ISSUED AS
STOCK DIVIDENDS (THE "PLAN").

                         PRINCIPAL FEATURES AND BENEFITS

AVAILABILITY. This Plan is available to registered holders of shares of Common
Stock or shares of any other class or series of stock of the Corporation which
have been determined from time to time to be eligible to participate in the Plan
by the Board of Directors of the Corporation (collectively, the "Eligible
Shares"). The Corporation will promptly notify the stockholders of any such
additional class or series of stock which the Board of Directors has determined
to be eligible to participate in the Plan.

PARTICIPATION. Any holder of record of Eligible Shares may participate in the
program at any time by signing an Authorization Form and returning it to
EquiServe Trust Company, N.A. as the agent designated by the Corporation to
administer the Plan (the "Plan Agent").

FRACTIONAL SHARES. The Plan allows fractions of shares of Common Stock to be
credited to a Participant's account.

NO BROKERAGE COMMISSIONS. Participants will pay no brokerage commissions.
Administrative charges for the operation of the Plan by the Plan Agent will be
paid by the Corporation.

HOLDING OF NEW SHARES. The additional shares of Common Stock issued under the
Plan will be held for Participants by the Plan Agent. Such shares will be
registered in the name of the Plan Agent or its nominee.

STATEMENTS OF ACCOUNT. Statements of account will be sent to all Participants by
the Plan Agent following each dividend payment date.

TERMINATION OF PARTICIPATION. Participation in the Plan can be terminated at any
time upon written notice to the Plan Agent.

TAX IMPLICATIONS. In general, dividends paid by the Corporation, whether in cash
or stock, to United States citizens, residents and corporations will be subject
to United States tax in the hands of the recipient at the ordinary income rates
on the amount of cash or the full fair market value of the stock.

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BEGINNING OF PARTICIPATION. Participation in the Plan becomes effective on the
next declaration date for dividends declared on the Eligible Shares following
receipt by the Plan Agent of a duly completed Authorization Form. Stockholders
who wish to participate in the Plan with respect to the payment of a particular
dividend must have their completed Authorization Forms in the hands of the Plan
Agent in advance of such DIVIDEND DECLARATION DATE, which is expected to be
approximately two weeks prior to the record date for payment of such dividend.

EFFECT OF PARTICIPATION. A stockholder who chooses to participate in the Plan (a
"Participant") elects thereby to receive new shares of Common Stock of the
Corporation which will be issued by the Corporation as stock dividends in lieu
of cash dividends on all the Eligible Shares of a class or series registered in
the name of such stockholder (including shares of Common Stock previously
acquired by such Participant pursuant to the Plan), less any applicable
withholding tax. Shares of Common Stock issued as stock dividends under the Plan
will be valued at 95% of the Average Market Price (as defined herein) for shares
of Common Stock.

        In general, dividends paid by the Corporation, whether in cash or stock,
to a United States citizen or resident will not be subject to backup tax
withholding unless such person fails to certify as to no loss of exemption from
backup withholding or otherwise fails to comply with the backup withholding
rules. United States corporations are not subject to backup withholding.

        Dividends paid, whether in cash or stock, to United States citizens,
residents or corporations generally will be subject to tax at ordinary income
rates in an amount equal, in the case of individuals, to the amount of the cash
or the full fair market value of the stock on the date of distribution, and in
the case of corporations, in a net amount equal to 30% of the cash or such
value. In addition, a Participant will recognize gain or loss when shares
received as stock dividends are sold or exchanged by the Participant after
receipt of certificates for such shares or withdrawal from or termination of the
Plan. The amount of such gain or loss will equal the difference between the
amount which the Participant receives for the shares and the tax basis therefor.
Such gain or loss will be capital gain or loss, provided the Participant holds
such shares as a capital asset on the date of sale or exchange. Capital gains
recognized after 1987 will be taxed at ordinary income rates.

        In general, dividends paid by the Corporation, whether in cash or stock,
to persons other than United States citizens, residents and corporation will be
subject to withholding of United States tax on the amount of cash or the full
fair market value of the stock.

        Stock dividends received by Canadian resident individuals generally will
be taxed as dividends by Canada. The amount to be included in income is limited,
however, to the increase in the paid-up capital of the Corporation resulting
from the issue of the shares as a stock dividend. Stock dividends received by
corporations and mutual fund trusts generally will not be taxed as dividends by
Canada. The United States withholding tax

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paid will also be regarded as a taxable cash dividend, but the tax may be
creditable against Canadian taxes within prescribed limitations or deductible
from income. Cash dividends received from the Corporation by Canadian residents
who do not elect to participate in the Plan will generally be fully taxable in
Canada. United States withholding tax on the dividends will be eligible for
foreign tax credits or deductions where applicable.

        The foregoing constitutes only a summary of the Plan. The Plan, its
terms and conditions and the tax considerations applicable thereto are described
in the following pages of this Circular and you are advised to read them
carefully before completing an authorization form. Questions regarding the Plan
can be addressed to the Plan Agent.

        If any interpretation of the Plan is required, the text of the section
entitled "The Plan - Description, Terms and Conditions" shall govern.

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                                    THE PLAN

                        DESCRIPTION, TERMS AND CONDITIONS

ELIGIBLE SHARES

        Shares of Common Stock, par value $1.00 per share (the "Common Stock"),
or shares of any other class or series of stock of Lafarge Corporation (the
"Corporation") which have been determined from time to time to be eligible to
participate in the Optional Stock Dividend Plan (the "Plan") by the Board of
Directors of the Corporation (collectively, the "Eligible Shares") are eligible
to participate in the Plan. The Corporation will promptly notify the
stockholders of any such additional class or series of stock which the Board of
Directors has determined to be eligible to participate in the Plan.

PARTICIPATION

        Except as provided under "Eligible Stockholders" below, a registered
holder of Eligible Shares (a "Stockholder") may participate in the Plan with
respect to any class or series of Eligible Shares that he or she holds.
Participation by a Stockholder in the Plan with respect to a particular class or
series of Eligible Shares may only be made (as indicated on the enclosed
Authorization Form) in respect of all, but not part of, the Eligible Shares of
that class or series held by such Stockholder.

ELIGIBLE STOCKHOLDERS

        Stockholders who are residents of Canada or the United States are
eligible to participate in the Plan. A Stockholder residing outside Canada and
the United States is also eligible to participate in the Plan unless the
Corporation or EquiServe Trust Company, N.A., as the agent designated by the
Corporation to administer the Plan (the Plan Agent"), has reason to believe that
such participation is not, at the time, permitted under the laws of the
jurisdiction in which such Stockholder resides.

        Beneficial owners of Eligible Shares whose shares are not registered in
their own names may participate in the Plan by having their Eligible Shares of
the class or series which they desire to enroll in the Plan transferred into
their own names, unless those shares are held in a specific segregated
registered account, such as a numbered or nominee account with a bank, trust
company or broker, in which case Eligible Shares held in such account may be
enrolled in the Plan by directing such bank, trust company or broker to complete
and return the Authorization Form on behalf of the beneficial owners thereof.

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        Stockholders who intend to enroll in the Plan are strongly urged to
ensure that all of their Eligible Shares (of the same or different class or
series of shares) which they intend to enroll in the Plan are registered in
exactly the same name and address.

        An Authorization Form will not be accepted from or on behalf of any
Stockholder who the Corporation or the Plan Agent has reason to believe is not
eligible to participate in the Plan.

ENROLLMENT

        A STOCKHOLDER WHO WISHES TO CONTINUE RECEIVING DIVIDENDS ON HIS ELIGIBLE
SHARES IN CASH IS NOT REQUIRED TO COMPLETE OR FILE ANY DOCUMENTS OR TAKE ANY
ACTION FOR THAT PURPOSE.

        To join the Plan, an eligible Stockholder must complete, sign and return
to the Plan Agent the enclosed Authorization Form if he or she elects to enroll
his or her Eligible Shares in the Plan. An addressed envelope is enclosed for
such purpose. Additional Authorization Forms are available from the Plan Agent
upon request. Once a Stockholder has enrolled in the Plan (a "Participant"),
participation continues in respect of his or her Eligible Shares enrolled in the
Plan (the "Participating Eligible Shares") until terminated by the Participant
or by the Corporation in accordance with the terms of the Plan.

        Stockholders who intend to enroll all of their Eligible Shares of any
class or series in the Plan and who have received more than one Authorization
Form for that class or series as a result of such shares being registered in
different names or addresses must return all of such Authorization Forms.
Stockholders are reminded that they may consolidate all their different accounts
by so advising the Plan Agent, and it is recommended that they do so.

        By completing an Authorization Form, with respect to each class or
series of Eligible Shares covered thereby, a Participant thereby authorizes and
directs the Corporation to pay dividends on all, but not part, of the Eligible
Shares of that class or series registered in his or her name by the issuance of
additional shares of Common Stock (after deduction of any applicable withholding
tax). Such shares will be delivered to the Plan Agent on behalf of the
Participants, and the Plan Agent will credit the account of each Participant
with the number of such shares to which such Participant is entitled. Shares of
Common Stock issued under the Plan will be registered in the name of the Plan
Agent or its nominee. Subsequent dividends payable on additional shares of
Common Stock acquired by a Participant pursuant to his or her participation in
the Plan will be payable in the form of additional shares of Common Stock issued
as stock dividends for the account of the Participant.

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        A Stockholder shall become a Participant in the Plan in respect of a
class or series of Eligible Shares effective as of the date of the next
declaration of dividends (the "Declaration Date") on such class or series of
Eligible Shares, following receipt by the Plan Agent of a duly completed
Authorization Form for that class or series. A Stockholder who wishes to
participate in the Plan with respect to a particular dividend on a class or
series of Eligible Shares must have his or her Authorization Form for that class
or series in the hands of the Plan Agent in advance of the relevant Declaration
Date for that class or series of Eligible Shares. If an Authorization Form is
received by the Plan Agent from a Stockholder on or after a particular
Declaration Date, that dividend will be paid to the Participant in the manner
specified by the Board of Directors of the Corporation for Stockholders not
participating in the Plan, and participation in the Plan will commence with the
following Declaration Date for that class or series of Eligible Shares.

        Dividend payment dates for the Common Stock are expected to be the first
business day of March, June, September and December. Declaration Dates may vary
but are approximately four weeks before the corresponding dividend payment
dates.

VALUATION AND PRICE OF ADDITIONAL SHARES OF COMMON STOCK

        On each dividend payment date for Participating Eligible Shares, the
Corporation will issue and deliver to the Plan Agent on behalf of Participants,
after deduction of any applicable withholding tax, the number of shares of
Common Stock distributed as stock dividends, computed in the manner described
below. Such additional shares of Common Stock will, in turn, be entitled to the
benefit of subsequence stock dividends under the Plan.

        Each Participant's account with the Plan Agent will be credited with the
numbers of shares of Common Stock including fractions thereof computed to four
decimal places, which is equal to the aggregate of cash dividends (after
deduction of any applicable withholding tax) which would otherwise be payable on
such Participant's Participating Eligible Shares and on all shares of Common
Stock held on behalf of such Participant by the Plan Agent under the Plan
divided by 95% of the applicable Average Market Price (as hereinafter defined).

        The average market price (the "Average Market Price") on any dividend
payment date will be (a) in respect of dividends on participating shares of
Common Stock, the average of the closing prices of a round lot of Common Stock
traced on the principal securities market on which the Common Stock is traded
(as determined by the Board of Directors of the Corporation) on the last five
trading days on which at least a round lot of Common Stock was traded, ending on
the business day immediately preceding the applicable dividend payment date for
the Common Stock, or (b) in respect of dividends on Participating Eligible
Shares of a class or series other than Common Stock, the average of the closing
prices of a round lot of Common Stock traced on the principal

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securities market on which the Common Stock is traded (as determined by the
Board of Directors of the Corporation) on the last five trading days on which at
least a round lot of Common Stock was traded, ending on the business day
immediately preceding the most recent dividend payment date for the Common
Stock, unless such dividend payment date precedes by more than five days the
dividend payment date for such class or series of Eligible Shares, in which case
the aforementioned calculation shall be made with reference to the period ending
on the dividend payment date for such class or series of Eligible Shares.

CERTIFICATES FOR ADDITIONAL SHARES OF COMMON STOCK

        Certificates for shares of Common Stock issued under the Plan will not
initially be issued to Participants but will be registered in the name of the
Plan Agent or its nominee. The number of shares of Common Stock issued under the
Plan for each Participant will be credited to a Plan account established for
that Participant and shown on his or her statement of account.

        A Participant may, without terminating his or her participation in the
Plan, upon written request to the Plan Agent, have certificates registered in
such Participant's name and delivered to such Participant for any number of
whole shares of Common Stock held for such Participant's account under the Plan.
Such requests must be mailed to EquiServe Shareholder Services, P.O. Box 8218,
Boston, MA 02266-8218. Normally such certificates will be issued to a
Participant within seven days following receipt by the Plan Agent of such
Participant's account under the Plan, and the Participant will remain enrolled
in the Plan.

        Accounts under the Plan will be maintained in the names in which stock
certificates of the Participants were registered at the time they entered the
Plan. As a result, stock certificates for whole shares of Common Stock will be
similarly registered when issued.

        Shares of Common Stock held by the Plan Agent under the Plan may not be
pledged, sold or otherwise disposed of by a Participant. A Participant who
wishes to pledge, sell or otherwise dispose of such shares must request that
certificates for such shares be issued to him or her.

        A certificate will not be issued for a fraction of a share.

STATEMENTS OF ACCOUNT

        The Plan Agent will maintain an account for each Participant. A
statement of account will be mailed to each Participant by the Plan Agent as
soon as practicable after each dividend payment date for Participating Eligible
Shares.

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        Each such statement will indicate, among other things, (a) the number of
additional whole shares of Common Stock and any fraction thereof to which such
Participant became entitle by reason of such dividend payment, and (b) as of a
date following such dividend payment date, the total number of whole shares of
Common Stock standing to the credit of such Participant in the Plan and any
fraction of a share of Common Stock held for the account of such Participant by
the Plan Agent.

        These statements are a Participant's continuing permanent record of the
value or price of the additional shares of Common Stock acquired under the Plan
and should be retained for tax purposes.

TERMINATION OF PARTICIPATION

        Participation in the Plan may be terminated in respect of any class or
series of Participating Eligible Shares by a Participant by written notice to
the Plan Agent at the address specified under the heading "Certificates for
Additional Shares of Common Stock." Termination of participation will become
effective on the declaration date for any dividend declared on such class or
series of Participating Eligible Shares immediately following receipt by the
Plan Agent of the notice of termination. If such notice is received by the Plan
Agent on or after the declaration date for any dividend declared on such class
or series of Participating Eligible Shares, termination will not become
effective until after the payment of such dividend. After termination, all
subsequent dividends on such class or series of Participating Eligible Shares
will be paid to the Stockholder in cash or in such other manner as may be
specified by the Board of Directors of the Corporation for Stockholders not
participating in the Plan.

        Participants are reminded that if the Participating Eligible Shares with
respect to which they desire to terminate participation in the Plan are
registered under different, or partially different, names and addresses, they
must ensure that they advise the Plan Agent as to each account which they desire
to terminate.

        Upon termination of participation in the Plan by a Participant of any
class or series of Participating Eligible Shares held by a Participant, such
Participant will be sent a stock certificate registered in his or her name
representing the number of whole shares of Common Stock held for the account of
such Participant, together with a cash payment for any fraction of a share of
Common Stock credited to such Participant's account based on the Average Market
Price prevailing on the last preceding dividend payment date for any class or
series of Eligible Shares.

        Participation in the Plan by any Participant will automatically
terminate in respect of all classes or series of Participating Eligible Shares
upon receipt by the Plan Agent of a written notice satisfactory to the Plan
Agent of the death of such Participant (in the case of a natural person) or
dissolution of such Participant (in the case of a corporation or other business
entity). In the event of such termination, and upon receipt by the Plan

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Agent of documentation satisfactory to it, the legal representative of or
successor in interest to such Participant will be sent a stock certificate
registered in his or her name representing the number of whole shares of Common
Stock held for the account of such Participant together with a cash payment for
any fraction of a share of Common Stock credited to such Participant's account
based on the Average Market Price prevailing on the last preceding dividend
payment date for any class or series of Eligible Shares.

        If a Participant disposes of all the shares of any class or series of
Eligible Shares registered in his or her name, the Participant shall direct the
disposition of the shares of Common Stock held by the Plan Agent for his or her
account under the Plan. Until the Plan Agent is otherwise notified, dividends
will continue to be paid on such shares by the issuance of additional shares of
Common Stock to the Plan Agent for the account of such Participant.

STOCKHOLDER VOTING

        Whole shares of Common Stock held for a Participant's account under the
Plan on the record date for a vote of Stockholders will be voted in the same
manner as the Participant's Eligible Shares of record are voted either by proxy
or by the Participant in person. Participants who cease to be Stockholders of
record will continue to receive the same information as Stockholders of record
so that shares held under the Plan may be voted in accordance with their
instructions. Shares for which instructions are not received will not be voted.

        Fractional shares of Common Stock credited to a Participant's account
will have voting rights.

RIGHTS OFFERINGS, STOCK SPLITS AND STOCK DIVIDENDS

        In the event that the Corporation makes available to its holders of
Common Stock rights to subscribe for additional shares of Common Stock or other
securities, Participants will be sent rights certificates for the aggregate
number of shares of Common Stock registered in the name of such Participant and
the additional whole shares of Common Stock standing to the credit of such
Participant in the Plan. No such rights will be made available in respect of
fractions of such shares held for the account of such Participant by the Plan
Agent.

        Any shares of Common Stock distributed as a result of a stock dividend
(other than a stock dividend paid to Participants in the Plan) on, or a stock
split of, shares held by the Plan Agent for the account of a Participant under
the Plan will be retained by the Plan Agent and credited proportionately to the
accounts of all Participants in the Plan. Stock certificates for any shares of
Common Stock resulting from a stock dividend (except as aforesaid) on, or a
stock split of, shares of Common Stock held of record by a

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Participant will be mailed directly to such Participant in the same manner as to
Stockholders not participating in the Plan.

RESPONSIBILITIES OF THE CORPORATION AND THE PLAN AGENT

        Neither the Corporation nor the Plan Agent shall be liable for any act
done in good faith or for any good faith omission to act nor shall the
Corporation or the Plan Agent have any duties, responsibilities or liabilities
except such as are expressly set forth in the Plan.

RISK OF MARKET PRICE FLUCTUATIONS

        A Participant's investment in shares of Common Stock acquired under the
Plan is recognized as being no different from an investment in shares of Common
Stock directly held. Accordingly, neither the Corporation nor the Plan Agent can
assure a profit or protect Participants against a loss on shares acquired under
the Plan and each Participant shall bear the risk of loss and enjoy the benefits
of any gain from market price with respect to shares of Common Stock acquired
under the Plan.

AMENDMENT, MODIFICATION, SUSPENSION OR TERMINATION OF THE PLAN

        The Corporation reserves the right to amend, modify, suspend or
terminate the Plan or participation therein, in whole or in part, or in regard
to any or all Participants, at any time, provided such action has no retroactive
effect that would prejudice the interests of Participants. All Participants will
be sent written notice of any such amendment, modification, suspension or
termination. If the Plan or participation therein is terminated in whole or in
part by the Corporation, a certificate for the additional whole shares of Common
Stock standing to the credit of each affected Participant will be issued
together with a cash payment for any fraction of a share of Common Stock based
on the Average Market Price prevailing on the last preceding dividend payment
date for any class or series of Eligible Shares. In the event of suspension of
the Plan by the Corporation, dividends payable on Participating Eligible Shares
after the effective date of suspension will be paid to the Participants in cash
or in such other manner as may be specified by the Board of Directors of the
Corporation.

NOTICES

        All communications with or notices required to be given to the Plan
Agent should be addressed to:

                      EquiServe Shareholder Services
                      Dividend Reinvest Section
                      P.O. Box 8218
                      Boston, MA 02266-8218

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        Additional Authorization Forms may be requested and inquiries made about
the Plan, by writing to the mailing address shown above or by calling the Plan
Agent at 1-800-633-4236.

        All communications with or notices required to be given to a Participant
will be sent to the Participant at the most recent address appearing on the list
of Stockholders maintained by the transfer agent of the Corporation or at a more
recent address as furnished in writing by the Participant to the Plan Agent in
the manner specified above.

ADMINISTRATION FEES

        Participants will pay no brokerage commissions in connection with shares
of Common Stock issued under the Plan, and all administrative charges for the
operation of the Plan by the Plan Agent will be paid by the Corporation.

APPLICATION OF FUNDS

        The funds which otherwise would have been paid out by the Corporation as
cash dividends and which are retained by the Corporation as a result of the
issuance of additional shares of Common Stock under the Plan will form part of
the Corporation's general funds and will provide additional working capital for
the Corporation.

PRINCIPAL STOCKHOLDER

        Lafarge S.A., which owned directly or indirectly 37,695,406 shares of
Common Stock (approximately 55.3% of the outstanding Common Stock) of the
Corporation as of June 30, 1999, is currently a participant in the Plan in
respect of all of the shares of Common Stock that it holds in several of its
affiliates. Under the provisions of the Plan, Lafarge S.A., as any other
Participant, may reinstate its participation thereunder at any time in respect
of any class or series of Participating Eligible Shares.

EFFECTIVE DATE

        The effective date of the Plan is August 1, 1983.

                                TAX CONSIDERATION

        The following is a summary of the income tax considerations relating to
participation in the Plan. These comments are based on the Canadian (federal and
Quebec) and United States federal tax legislation currently in effect.

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        Any Stockholder who wishes to participate in the Plan should consult his
or her tax adviser as to the tax consequences in his or her country of
residence.

U.S. FEDERAL INCOME TAX CONSIDERATIONS

        Dividends paid, whether in cash or stock, to United States citizens,
residents or corporations generally will be subject to tax at ordinary income
rates in an amount equal, in the case of individuals, to the amount of the cash
or the full fair market value of the stock on the date of distribution, and in
the case of corporations, in a net amount equal to 30% of the cash or such
value. The basis of shares distributed as stock dividends will equal their fair
market value on the date of distribution, and their holding period will begin on
the day following the date of distribution.

        A Participant will not realize taxable income when the Participant
receives certificates for whole shares credited to the Participant's account,
either upon the Participant's request for certain of those shares or upon
withdrawal from or termination of the Plan. A Participant will recognize gain or
loss when shares are sold or exchanged by the Participant after receipt of
certificates for such shares or upon withdrawal from or termination of the Plan.
A Participant will recognize gain or loss when shares are sold or exchanged by
the Participant after receipt of certificates for such shares or withdrawal from
or termination of the Plan. In the case of a fractional share, a Participant
will recognize gain or loss when the Participant receives a cash adjustment for
a fraction of a share credited to the Participant's account upon withdrawal from
or termination of the Plan. The amount of such gain or loss will equal the
difference between the amount which the Participant receives for the shares or
fraction of a share and the tax basis therefor. Such gain or loss will be
capital gain or loss, provided the Participant holds such shares as a capital
asset on the date of the sale or exchange. Capital gains recognized after 1987
will be taxed at ordinary income rates.

        Dividends paid, whether in cash or stock, to a United States citizen or
resident may be subject to United States backup withholding at the rate of 31%
of the cash or the full fair market value of the stock on the date of
distribution unless such person (a) is a corporation or comes within certain
other exempt categories and, when required, demonstrates this fact; or (b)
provides a taxpayer identification number (social security number for
individuals), certifies as to no loss of exemption from backup withholding, and
otherwise complies with applicable requirements of the backup withholding rules.

        Dividends paid, whether in cash or stock, to Canadian resident
individuals who are not United States citizens or residents and as to whom the
dividends are not effectively connected with a United States trade or business
and to Canadian corporations as to which the dividends are not so effectively
connected, generally will be subject to United States withholding tax at the
rate of 15% of the cash or the full fair market value of the stock on the date
of distribution under the applicable income tax treaty.

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        Dividends paid, whether in cash or stock, to persons resident in other
countries who are not United States citizens or residents and as to whom the
dividends are not effectively connected with a United States trade or business
generally will be subject to United States withholding tax at the rate of 30% of
the cash or the full fair market value of the stock on the date of distribution
or, if an income tax treaty is in effect between the country of the recipient
and the United States, at the lower treaty rate.

        In measuring the amount of the dividend for United States tax purposes,
the shares will be valued at their full fair market value, not at 95% thereof.

CANADIAN INCOME TAX CONSIDERATIONS

        Canadian resident individuals receiving a stock dividend from the
Corporation will generally be regarded as receiving a dividend includable in
income for Canadian federal or Quebec income tax purposes in an amount equal to
the increase in the paid-up capital of the Corporation by virtue of the payment
of the stock dividend, which amount will be $1.00 per share so issued. The cost
of the shares received will be the same amount. Stock dividends received by
corporations and mutual fund trusts will not be taxed as dividends and the cost
of the shares received will be nil. After receipt of the stock dividend, the
average cost of all the shares of the class or series held by the Participant
may therefore be reduced for tax purposes. It is considered that no taxable
benefit will arise as a result of the granting of a right to receive stock
dividends calculated at 95% of the Average Market Price, or as a result of the
exercise of such a right.

        The United States withholding tax of 15% deducted by the Corporation
will be regarded for Canadian federal and Quebec income tax purposes as a cash
dividend received by the Participant and must be included in the Participant's
income. The United States tax withheld may be available to the Participant as a
credit against Canadian taxes otherwise payable within prescribed limitations or
as a deduction in computing the Participant's income. Special rules are
applicable whether a corporation owns, directly or indirectly, not less than 10%
of any class of shares in the Corporation.

        Cash dividends received from the Corporation by Canadian residents who
do not elect to participate in the Plan will generally be fully taxable in
Canada. United States withholding tax on the dividends will be eligible for
foreign tax credits or deductions where applicable.

September 1999

                                       13<PAGE>   1
                                                                   EXHIBIT 10.27

               NON-EMPLOYEE DIRECTORS' DEFERRED COMPENSATION PLAN
                    CASH OR PHANTOM STOCK INVESTMENT OPTIONS

Each year, directors may elect to defer payment of their fees for that year
until termination of their service as a director. Any such election must be made
prior to that year's annual stockholder meeting and must specify one of two
payment options--lump sum or up to ten annual installments. Effective for May
2001, directors may elect either to have their deferred fees bear interest
computed quarterly at the average prime rate for the quarter or to invest their
deferred fees (in increments from 10% to 100%) in "phantom" shares of the
Company's common stock. Investments in phantom shares will be valued at the NYSE
closing price of the Company's common stock on the date non-deferred fees would
be payable. Dividends will be credited to deferred phantom shares and will be
reinvested in additional phantom shares at the NYSE closing price on the
dividend payment date. Directors may change existing deferred compensation
investments (from cash to phantom shares or vice versa) each quarter during
prescribed window periods. Phantom shares will have no voting rights and may not
be sold or transferred. Distributions from phantom shares will be valued at the
NYSE closing price of the Company's common stock on the last trading day before
the payment date.

PHANTOM STOCK INVESTMENT RULES

-       Directors may elect to invest deferred fees in phantom stock in
        increments of 10% up to 100%. The initial election for investing future
        fees in phantom stock must be made at the time of the annual deferral
        election.

-       Investments in phantom shares will be valued at the Lafarge Corporation
        closing price on the New York Stock Exchange on the date that
        non-deferred fees would be payable. If Lafarge stock is not traded on
        that date, the shares will be valued at the closing price of the most
        recent prior trading day.

-       Dividends will be credited to the deferred phantom shares on the regular
        dividend payment dates and will be reinvested in additional phantom
        shares at the NYSE closing price on the dividend payment date.

-       Directors may change existing deferred compensation investments into
        phantom shares from cash or out of phantom shares to cash only during
        the 10 business days beginning on the 3rd business day after Lafarge
        Corporation's public release of quarterly results by providing a written
        request to the Corporate Secretary. Investments of current deferred
        balances into or out of phantom shares will be valued at the NYSE
        closing price on the date that the Corporate Secretary receives the
        transfer request.

                                       1
<PAGE>   2

-       Former directors may continue to change investments of their unpaid
        deferred compensation balances under the same process. After the former
        director ceases to be an "Affiliated Person," they may change their
        investment options in any month. Such investment changes will be
        effective on the first day of the month following the month in which the
        Corporate Secretary receives written notice of the investment change.
        Phantom shares so changed will be valued at the NYSE closing price of
        the stock on the last trading day of the month in which the notice is
        received.

-       Phantom shares have no voting rights and may not be sold or transferred.
        The number of phantom shares held in a director's deferred compensation
        account on December 31 of each year will be included in required
        disclosures of their holdings.

-       In the event that Lafarge Corporation is merged or acquired, or due to
        any other transaction, the common stock of the corporation is no longer
        publicly traded, any deferred compensation investments held in phantom
        shares at the time of such transaction will be converted to cash value
        at the final trading price on the last day that the stock is publicly
        traded.

DISTRIBUTIONS OF DEFERRED COMPENSATION

-       Distributions will be made in accordance with the election made by the
        director, either as a lump sum or in up to ten annual installments. The
        initial distribution will take place on January 31 of the year following
        the calendar year in which the director's service is terminated. If
        January 31 is not a business day, the distribution will be on the last
        business day before January 31.

-       Directors may change their distribution election up until one year prior
        to the date of their termination of board service, by notifying the
        Corporate Secretary in writing. At the date of termination, the most
        recent distribution election that has been on file with the Corporate
        Secretary for at least one full year will be binding.

-       All distributions of deferred directors' compensation will be in cash.
        Distributions from accounts invested in phantom shares will be valued at
        the NYSE closing price of the stock on the last trading day before the
        payment dated.

-       If a director's deferred compensation account is invested in both cash
        and phantom shares on the date of an annual installment distribution,
        the distribution will be subtracted from the cash and stock portions of
        the account in proportion to the investments. For example, if the
        account is invested 60% in phantom shares and 40% in cash, the
        installment will be made 60% from the stock investment and 40% from the
        cash investment.

                                       2
<PAGE>   3

-       In the event of the death of a director or former director prior to the
        full distribution of his/her deferred compensation account, the entire
        remaining balance will be paid in cash to the director's beneficiary
        within 30 days after the Corporate Secretary receives formal
        certification of the death. If no beneficiary has been designated by the
        director, the unpaid balance will be paid to his or her estate.
        Directors or former directors may change their beneficiary designation
        at any time by providing written notification to the Corporate
        Secretary.

                                       3
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