<PAGE>

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                               -------------------

                                    FORM 10-Q

         [X]   QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF
                       THE SECURITIES EXCHANGE ACT OF 1934

                  For quarterly period ended September 30, 2003

         [ ]    TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

            For the transition period from _______ to _______________

                          Commission File Number 1-5341

                                     ELKCORP
           -----------------------------------------------------------
             (Exact name of Registrant as specified in its charter)

            DELAWARE                                                 75-1217920
-------------------------------                               ------------------
(State or other jurisdiction of                                 (I.R.S. Employer
incorporation or organization)                               Identification No.)

14911 QUORUM DRIVE, SUITE 600, DALLAS, TEXAS                          75254-1491
--------------------------------------------                          ----------
(Address of principal executive offices)                              (Zip Code)

Registrant's telephone number, including area code                (972) 851-0500

         Indicate by check mark whether the Registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
Registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days. Yes [X]. No [ ].

         Indicate by check mark whether the Registrant is an accelerated filer
(as defined in Rule 12b-2 of the Exchange Act). Yes [X]. No [ ].

         As of close of business on October 31, 2003, the Registrant had
outstanding 19,614,878 shares of Common Stock, par value $1 per share.

<PAGE>

                            ELKCORP AND SUBSIDIARIES

                    FOR THE QUARTER ENDED SEPTEMBER 30, 2003

                                      INDEX

<TABLE>
<CAPTION>
                                                                                      Page
                                                                                      ----
<S>                                                                                   <C>
PART I. FINANCIAL INFORMATION (UNAUDITED)

     Item 1. Financial Statements

             Consolidated Balance Sheets as of September 30, 2003 and June 30, 2003       1
             Consolidated Statements of Operations for the Three Months Ended
             September 30, 2003 and 2002                                                  2
             Consolidated Statements of Cash Flows for the Three Months Ended
             September 30, 2003 and 2002                                                  3
             Notes to Consolidated Financial Statements                                4-12

     Item 2. Management's Discussion and Analysis of Financial Condition
             and Results of Operations                                                13-19

     Item 3. Quantitative and Qualitative Disclosures About Market Risk                  20

     Item 4. Controls and Procedures                                                     20

PART II. OTHER INFORMATION

     Item 6. Exhibits and Reports on Form 8-K                                            21

SIGNATURES                                                                               22
</TABLE>

<PAGE>

PART I. FINANCIAL INFORMATION

ITEM 1. FINANCIAL STATEMENTS

                            ELKCORP AND SUBSIDIARIES
                           CONSOLIDATED BALANCE SHEETS
                           (Unaudited, $ in thousands)

<TABLE>
<CAPTION>
                                                                         September 30,     June 30,
                                                                             2003            2003
                                                                         -------------   ------------
<S>                                                                      <C>             <C>
ASSETS
CURRENT ASSETS
Cash and cash equivalents                                                $     22,759    $      5,056
Trade receivables, less allowance of $1,016 and $1,029                        117,477         120,268
Inventories -
         Finished goods                                                        31,500          44,647
         Work-in-process                                                          153              94
         Raw materials                                                          8,424           9,353
                                                                         ------------    ------------
         Total inventories                                                     40,077          54,094
                                                                         ------------    ------------

Prepaid expenses and other                                                      4,556           6,723
Deferred income taxes                                                           2,872           2,654
                                                                         ------------    ------------
                  Total current assets                                        187,741         188,795
                                                                         ------------    ------------

PROPERTY, PLANT AND EQUIPMENT, AT COST                                        385,453         368,381
         Less - accumulated depreciation                                     (135,703)       (131,114)
                                                                         ------------    ------------
                  Property, plant and equipment, net                          249,750         237,267
                                                                         ------------    ------------

OTHER ASSETS                                                                   14,206          16,075
                                                                         ------------    ------------
                                                                         $    451,697    $    442,137
                                                                         ============    ============

LIABILITIES AND SHAREHOLDERS' EQUITY
CURRENT LIABILITIES
Accounts payable                                                         $     35,640    $     35,971
Accrued liabilities                                                            20,935          19,568
                                                                         ------------    ------------
                  Total current liabilities                                    56,575          55,539
                                                                         ------------    ------------

LONG-TERM DEBT                                                                150,492         152,526
DEFERRED INCOME TAXES                                                          39,392          37,544

SHAREHOLDERS' EQUITY -

         Common stock ($1 par, 19,988,074 shares issued)                       19,988          19,988
         Paid-in-capital                                                       56,989          57,331
         Unearned compensation - unvested restricted stock                       (403)           (385)
         Retained earnings                                                    135,125         126,969
                                                                         ------------    ------------
                                                                              211,699         203,903
         Less - Treasury stock (378,037 and 451,185 shares, at cost)           (6,461)         (7,375)
                                                                         ------------    ------------
                  Total shareholders' equity                                  205,238         196,528
                                                                         ------------    ------------
                                                                         $    451,697    $    442,137
                                                                         ============    ============
</TABLE>

See accompanying notes to consolidated financial statements.

                                      - 1 -

<PAGE>

                            ELKCORP AND SUBSIDIARIES
                      CONSOLIDATED STATEMENTS OF OPERATIONS
                           (Unaudited, $ in thousands
                             except per share data)

<TABLE>
<CAPTION>
                                                                   Three Months Ended
                                                                      September 30,
                                                               ---------------------------
                                                                   2003           2002
                                                               ------------   ------------
<S>                                                            <C>            <C>
SALES                                                          $    161,344   $    120,082
                                                               ------------   ------------

COST AND EXPENSES
       Cost of sales                                                128,955         95,428
       Selling, general and administrative:
           Other selling, general and administrative                 16,222         14,102
           Noncash stock option compensation                             --         (5,378)
                                                               ------------   ------------
INCOME FROM OPERATIONS                                               16,167         15,930
                                                               ------------   ------------

OTHER EXPENSE
       Interest expense, net                                          1,383          1,680
                                                               ------------   ------------

INCOME BEFORE INCOME TAXES                                           14,784         14,250
       Provision for income taxes                                     5,647          5,254
                                                               ------------   ------------
NET INCOME                                                     $      9,137   $      8,996
                                                               ============   ============

NET INCOME PER SHARE-BASIC                                     $        .47   $        .46
                                                               ============   ============

NET INCOME PER SHARE-DILUTED                                   $        .46   $        .46
                                                               ============   ============

DIVIDENDS PER COMMON SHARE                                     $        .05   $        .05
                                                               ============   ============

AVERAGE COMMON SHARES OUTSTANDING (000's)
       Basic                                                         19,545         19,461
                                                               ============   ============
       Diluted                                                       19,823         19,595
                                                               ============   ============
</TABLE>

See accompanying notes to consolidated financial statements.

                                      - 2 -

<PAGE>

                            ELKCORP AND SUBSIDIARIES
                      CONSOLIDATED STATEMENTS OF CASH FLOWS
                           (Unaudited, $ in thousands)

<TABLE>
<CAPTION>
                                                                              Three Months Ended
                                                                                 September 30,
                                                                         ----------------------------
                                                                             2003            2002
                                                                         ------------    ------------
<S>                                                                      <C>             <C>
CASH FLOWS FROM OPERATING ACTIVITIES

         Net income                                                      $      9,137    $      8,996
         Adjustments to reconcile net income
            to net cash provided by operating activities:

                  Depreciation and amortization                                 4,667           4,550
                  Deferred income taxes                                         1,630           2,615
                  Changes in assets and liabilities:
                     Trade receivables                                          2,791          15,077
                     Inventories                                               14,017         (10,296)
                     Prepaid expenses and other                                 2,167           3,158
                     Accounts payable and accrued liabilities                   1,036          (6,187)
                                                                         ------------    ------------

                  Net cash provided by operating activities                    35,445          17,913
                                                                         ------------    ------------

CASH FLOWS FROM INVESTING ACTIVITIES

         Additions to property, plant and equipment                           (17,163)         (7,575)
         Other                                                                   (140)           (676)
                                                                         ------------    ------------

                  Net cash used for investing activities                      (17,303)         (8,251)
                                                                         ------------    ------------

CASH FLOWS FROM FINANCING ACTIVITIES

         Dividends on common stock                                               (980)           (973)
         Proceeds from stock option purchases                                     541              23
                                                                         ------------    ------------

                  Net cash used for financing activities                         (439)           (950)
                                                                         ------------    ------------

NET INCREASE IN CASH AND CASH EQUIVALENTS                                      17,703           8,712

CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR                                  5,056          12,436
                                                                         ------------    ------------

CASH AND CASH EQUIVALENTS AT END OF PERIOD                               $     22,759    $     21,148
                                                                         ============    ============
</TABLE>

See accompanying notes to consolidated financial statements.

                                      - 3 -

<PAGE>

                            ELKCORP AND SUBSIDIARIES
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                                   (Unaudited)

NOTE 1 - GENERAL

         The attached condensed consolidated financial statements have been
prepared pursuant to the rules and regulations of the Securities and Exchange
Commission. As a result, certain information and footnote disclosures normally
included in financial statements prepared in accordance with accounting
principles generally accepted in the United States of America have been
condensed or omitted. The company believes that the disclosures included herein
are adequate to make the information presented not misleading. These condensed
consolidated financial statements should be read in conjunction with the
consolidated financial statements and related notes included in the company's
Annual Report on Form 10-K for the fiscal year ended June 30, 2003. The
unaudited financial information contained herein has been prepared in conformity
with accounting principles generally accepted in the United States of America on
a consistent basis and does reflect all adjustments (consisting of normal
recurring accruals) which are, in the opinion of management, necessary for a
fair presentation of the results of operations for the three-month periods ended
September 30, 2003 and 2002. Because of seasonal, weather-related conditions in
some of the company's market areas, sales can vary at times, and results of any
one quarter or other interim reporting period should not necessarily be
considered as indicative of results for a full fiscal year.

NOTE 2 - COMPANY SEGMENTS

         The Building Products segment consists of Elk Premium Building
Products, Inc. and its operating subsidiaries (collectively Elk). These
companies manufacture (1) premium laminated fiberglass asphalt shingles, (2)
coated and non-coated nonwoven fabrics used in asphalt shingles and other
applications in the building and construction, filtration, floor coverings and
other industries, and (3) nontoxic composite wood decking, marine dock, and
fencing products. Building Products accounted for 98% and 94% of consolidated
sales during the three-month periods ended September 30, 2003 and 2002,
respectively.

         Other, Technologies consists of the company's other operations. These
dissimilar operations are combined, as none individually meets the materiality
criteria for separate segment reporting. In fiscal 2003, operating profit from
the company's Engineering, Technologies business, which provides proprietary
technologies and related engineering services to the natural gas processing
industry as Ortloff Engineers, LTD (Ortloff), exceeded 10% of consolidated
operating profit. In accordance with Financial Accounting Standards Board (FASB)
Statement of Financial Accounting Standards (SFAS) No. 131, "Disclosures about
Segments of an Enterprise and Related Information," this business was presented
as a separate segment in fiscal 2003 because it exceeded this quantitative
threshold. However, this business has not historically met the 10% reporting
test, is not expected to in fiscal 2004, nor will it typically be expected to in
the future. Accordingly, this business is included in Other, Technologies in
fiscal 2004. Other, Technologies also includes Cybershield, Inc. and its
operating subsidiary (collectively Cybershield), which applies precise
conductive metal coatings to plastic components utilized in electronics
enclosures to control the

                                     - 4 -

<PAGE>

electromagnetic and radio frequency emissions of such devices, and to create
circuitry and antennae for digital cellular phones, consumer electronics, and
other electronic products; and Chromium Corporation (Chromium), which is a
leading provider of hard chrome and other surface finishes designed to extend
the life of steel machinery components operating in abrasive environments. An
additional operation, Elk Technologies, Inc., develops and markets fabrics
featuring VersaShield fire retardant coatings designed for use outside of
traditional building products applications, including home furnishings and other
consumer products. This business has not yet produced significant commercial
sales.

Financial information by company segment is summarized as follows:

<TABLE>
<CAPTION>
                                                                                (In thousands)
                                                                              Three Months Ended
                                                                                 September 30,
                                                                         ----------------------------
                                                                             2003            2002
                                                                         ------------    ------------
<S>                                                                      <C>             <C>
SALES
Building Products                                                        $    157,367    $    113,316
Other, Technologies                                                             3,977           6,766
                                                                         ------------    ------------
                                                                         $    161,344    $    120,082
                                                                         ============    ============
OPERATING PROFIT (LOSS)
Building Products                                                        $     21,904    $     14,498
Other, Technologies                                                            (2,063)         (1,089)
Corporate and other, excluding noncash stock option compensation               (3,674)         (2,857)
Noncash stock option compensation                                                  --           5,378
                                                                         ------------    ------------
                                                                               16,167          15,930
Interest expense, net                                                          (1,383)         (1,680)
                                                                         ------------    ------------
Income before income taxes                                               $     14,784    $     14,250
                                                                         ============    ============

DEPRECIATION AND AMORTIZATION
Building Products                                                        $      3,551    $      3,415
Other, Technologies                                                               486             452
Corporate                                                                         630             683
                                                                         ------------    ------------
                                                                         $      4,667    $      4,550
                                                                         ============    ============
CAPITAL EXPENDITURES
Building Products                                                        $     15,568    $      6,994
Other, Technologies                                                               169             146
Corporate                                                                       1,426             435
                                                                         ------------    ------------
                                                                         $     17,163    $      7,575
                                                                         ============    ============
</TABLE>

<TABLE>
<CAPTION>
                                                                         September 30,     June 30,
                                                                             2003            2003
                                                                         -------------   ------------
<S>                                                                      <C>             <C>
IDENTIFIABLE ASSETS
Building Products                                                        $    371,396    $    376,110
Other, Technologies                                                            37,228          38,142
Corporate                                                                      43,073          27,885
                                                                         ------------    ------------
                                                                         $    451,697    $    442,137
                                                                         ============    ============
</TABLE>

                                     - 5 -

<PAGE>

NOTE 3 - PRODUCT SALES

         The following table summarizes sales by product category, excluding
intercompany sales for the three-month periods ended September 30, 2003 and
September 30, 2002:

<TABLE>
<CAPTION>
                                                                                (In thousands)
                                                                              Three Months Ended
                                                                                 September 30,
                                                                         ----------------------------
                                                                             2003            2002
                                                                         ------------    ------------
<S>                                                                      <C>             <C>
Premium roofing                                                          $    147,661    $    105,007
Performance nonwoven fabrics                                                    8,974           8,309
Composite building products                                                       732              --
Technology licensing and consulting fees                                          450             195
Conductive metal coatings                                                       1,605           4,605
Hard chrome and other surface finishes                                          1,922           1,966
                                                                         ------------    ------------
                                                                         $    161,344    $    120,082
                                                                         ============    ============
</TABLE>

NOTE 4 - COMPREHENSIVE INCOME

         Total comprehensive income for the three-month periods ended September
30, 2003 and September 30, 2002 were as follows:

<TABLE>
<CAPTION>
                                                                                (In thousands)
                                                                              Three Months Ended
                                                                                 September 30,
                                                                         ----------------------------
                                                                             2003            2002
                                                                         ------------    ------------
<S>                                                                      <C>             <C>
Net income                                                               $      9,137    $      8,996
Derivative transactions                                                            --             (16)
                                                                         ------------    ------------
Total comprehensive income                                               $      9,137    $      8,980
                                                                         ============    ============
</TABLE>

         At September 30, 2003, there are no derivative transactions in effect
that will cause net income to vary from total comprehensive income in future
periods.

                                     - 6 -

<PAGE>

NOTE 5 - EARNINGS PER SHARE

         Basic earnings per share is computed based on the average number of
common shares outstanding. Diluted earnings per share includes outstanding stock
options and restricted shares. Stock options to purchase 726,630 and 1,539,209
shares of common stock were excluded from the computation of diluted earnings
per share for the three-month periods ended September 30, 2003 and 2002,
respectively, as their effect would have been anti-dilutive. The following table
sets forth the computation of basic and diluted earnings per share:

<TABLE>
<CAPTION>
                                                                                (In thousands)
                                                                              Three Months Ended
                                                                                 September 30,
                                                                         ----------------------------
                                                                             2003            2002
                                                                         ------------    ------------
<S>                                                                      <C>             <C>
Net income                                                               $      9,137    $      8,996
                                                                         ============    ============

Denominator for basic earnings
  per share - weighted average
  shares outstanding                                                           19,545          19,461

Effect of dilutive securities:
  Restricted shares and employee stock options                                    278             134
                                                                         ------------    ------------

Denominator for dilutive earnings per share - adjusted weighted
average shares and assumed issuance of shares purchased under
incentive stock option plan and vesting of restricted shares using the
treasury stock method                                                          19,823          19,595
                                                                         ============    ============

Basic earnings per share                                                 $        .47    $        .46
                                                                         ============    ============

Diluted earnings per share                                               $        .46    $        .46
                                                                         ============    ============
</TABLE>

                                     - 7 -

<PAGE>

NOTE 6 - ACCOUNTING FOR STOCK-BASED COMPENSATION

         The company applies APB Opinion No. 25, "Accounting for Stock Issued to
Employees," and its related interpretations to measure compensation expense for
stock-based compensation plans. Refer to Note 7 - Noncash Stock Option
Compensation on page 9 of this Form 10-Q for a more detailed description of the
company's application of APB No. 25. If compensation cost for stock-based
compensation plans had been determined under SFAS No. 123, pro forma net income,
stock option compensation expense, and basic and diluted earnings per common
share for the three-month periods ended September 30, 2003 and 2002, assuming
all options granted in 1996 and thereafter were valued at grant date using the
Black-Scholes model, would have been as follows (in thousands, except per share
amounts):

<TABLE>
<CAPTION>
                                                                                (In thousands)
                                                                              Three Months Ended
                                                                                 September 30,
                                                                         ----------------------------
                                                                             2003            2002
                                                                         ------------    ------------
<S>                                                                      <C>             <C>
Net Income:

As reported                                                              $      9,137    $      8,996
Add:  Stock-based employee
      compensation expense
      (benefit) included in reported
      net income, net of related tax effects                                       --          (3,496)
Deduct:Total stock-based compensation expense determined under
      fair value based method for all awards granted since
      January 1, 1996, net of related tax effects                                (554)           (513)
                                                                         ------------    ------------
Pro forma                                                                $      8,583    $      4,987
                                                                         ============    ============

Earnings per common share:

  Basic - as reported                                                    $        .47    $        .46
                                                                         ------------    ------------

  Basic - pro forma                                                      $        .44    $        .26
                                                                         ------------    ------------

  Diluted - as reported                                                  $        .46    $        .46
                                                                         ------------    ------------

  Diluted - pro forma                                                    $        .43    $        .25
                                                                         ------------    ------------
</TABLE>

                                     - 8 -

<PAGE>

NOTE 7 - NONCASH STOCK OPTION COMPENSATION

         The company's 1998 Incentive Stock Option Plan contained a cashless
exercise provision that permitted an optionee to relinquish vested options to
the company in exchange for common shares having a current market value equal to
the net exercised market value of the relinquished options. Under APB No. 25,
the aforementioned cashless relinquishment feature can cause options issued
under the 1998 Plan to be considered stock appreciation rights (SAR's) in
substance, if not in form, unless past experience and economic incentives
indicate that optionees are more likely to exercise, rather than relinquish, the
options. Under APB No. 25, SAR's are accounted for using "variable" accounting
whereby income is charged (or credited) during each accounting period to reflect
any excess of the market value of shares underlying vested SAR's, over the
exercise price of vested SAR's.

         It was never the company's intention to issue SAR's under the 1998
Plan. In keeping with the company's original intent, effective August 13, 2002,
the Compensation Committee of the Board of Directors terminated the availability
of the relinquishment alternative under the 1998 Plan. Based on this action,
together with a decline in the company's share price subsequent to June 30,
2002, the company recorded a reversal of fiscal 2002 noncash stock option
compensation expense of $5,378,000 in the first quarter of fiscal 2003.
Subsequent to August 13, 2002, the company is again utilizing the "fixed" method
of stock option accounting.

NOTE 8 - LONG-TERM DEBT

         Senior Notes (Notes) having a principal balance of $145,000,000 were
outstanding at September 30, 2003. In June 2002, the company entered into an
interest rate swap to effectively convert the interest rate from fixed to
floating on $60,000,000 of debt through 2012. For this fair value hedge, both
the fair value of the derivative and the underlying hedged item are reported in
the balance sheet. Changes in the fair value of the derivative and the
underlying hedged item offset and are recorded each period in other income or
expense, as applicable. Accordingly, long-term debt reflected on the balance
sheet is summarized as follows:

<TABLE>
<CAPTION>
                                      September 30,    June 30,
(In thousands)                            2003           2003
-----------------------------------------------------------------
<S>                                   <C>            <C>
Senior Notes - principal balance      $    145,000   $    145,000
Fair value of interest rate swap             5,492          7,526
                                      ------------   ------------
                                      $    150,492   $    152,526
                                      ============   ============
</TABLE>

         The company also has $100,000,000 of primary credit available under a
Revolving Credit Facility (Facility), including up to a maximum of $10,000,000
in letters of credit through November 30, 2005. No borrowings were outstanding
on the Facility at September 30, 2003, although letters of credit totaling
$2,597,000 were outstanding.

                                      - 9 -

<PAGE>

NOTE 9 - PRODUCT WARRANTIES

         The company provides its customers with limited warranties on certain
products. Limited warranties relating to products sold by the Building Products
segment generally range from 20 to 50 years. Warranties relating to the Other,
Technologies companies are not significant to their operations. Warranty
reserves are established based on known or probable claims, together with
historical experience factors. The company periodically assesses the adequacy of
its recorded warranty liability and adjusts the amount as necessary. Changes in
the company's warranty liability during the current year period were as follows:

<TABLE>
<CAPTION>
                                       Warranty
(in thousands)                         Liability
--------------------------------------------------
<S>                                   <C>
Balance at June 30, 2003              $      2,675
Amounts charged to expense                     530
Warranty settlements                          (475)
                                      ------------
Balance at September 30, 2003         $      2,730
                                      ============
</TABLE>

NOTE 10 - ENVIRONMENTAL RISK

         Chromium has engaged in limited remediation activities at its former
plating operation in Lufkin, Texas. Soil sampling results from a pre-closing
environmental evaluation of the site indicated the necessity of localized
cleanup. Chromium has entered the property into the Texas Voluntary Cleanup
Program (VCP). Under this program, the Texas Commission on Environmental Quality
(TCEQ) reviews the voluntary cleanup plan the applicant submits, and, when the
work is complete, issues a certificate of completion, evidencing cleanup to
levels protective of human health and the environment and releasing prospective
purchasers and lenders from liability to the state. Properties entered into the
VCP are protected from TCEQ enforcement actions.

         Under the VCP, Chromium submitted a testing program, which the TCEQ has
approved, for a supplemental groundwater and soil assessment at the facility.
This program was designed to, among other things, further define the cleanup
requirements at the site. Once the investigation is complete, Chromium intends
to clean up the site under the VCP to a site specific risk-based cleanup
standard as prescribed by the Texas Risk Reduction Program. Preliminary results
from recent groundwater and soil assessments indicate that there has been no
environmental impairment beyond company property boundaries or to any
groundwater. However, until Chromium has the final results from its supplemental
assessment and TCEQ approval of a cleanup plan, the range of costs to remediate
the site are not determinable, nor can the company determine at this point in
time if it is reasonably possible that it will incur material additional costs
at the site. If a remediation plan similar to a plan successfully used at
another Chromium plant is approved by TCEQ, remediation costs will be immaterial
to the company's consolidated results of operations, financial position and
liquidity. However, other potential scenarios, none of which are reasonably
expected at this time, could potentially result in material

                                     - 10 -

<PAGE>

costs to the company. By December 31, 2003, management currently believes that a
range of exposure may be determinable. Therefore, the company currently believes
sufficient information for establishing a reserve for this environmental
exposure in accordance with SFAS No. 5, "Accounting for Contingencies," may be
available by December 31, 2003, and further anticipates that it may be in a
position at that time to determine if it is reasonably possible that the company
will incur material additional costs with regard to this site. The company's
ability to make such determinations within that time frame depends in part on
regulatory response times and other factors it does not control.

         The company's operations are subject to extensive federal, state and
local laws and regulations relating to environmental matters. Other than the
possible costs associated with the previously described Chromium matter, the
company does not believe it will be required to expend amounts which will have a
material adverse effect on the company's consolidated financial position or
results of operations by reason of environmental laws and regulations. Such laws
and regulations are frequently changed and could result in significantly
increased cost of compliance. Further, certain of the company's manufacturing
operations utilize hazardous materials in their production processes. As a
result, the company incurs costs for recycling or disposal of such materials and
may incur costs for remediation activities at its facilities and off-site from
time to time. The company establishes and maintains reserves for such known
remediation activities in accordance with SFAS No. 5.

NOTE 11 - INCOME TAXES

         In August 2003, the Internal Revenue Service (IRS) completed audits of
the company's consolidated tax returns through fiscal 2001. A notice of proposed
adjustment disallowing the timing of certain deductions for tax years 1998
through 2001 was rendered in connection with these audits. If the entire
proposed adjustment were upheld, noncurrent deferred income taxes would be
reduced by approximately $6,600,000, a $2,900,000 income tax receivable would be
reversed, and a $3,700,000 cash payment for income taxes payable would be
required. The proposed adjustment would have no impact on net income or earnings
per share. The company does not agree with the IRS proposed adjustment and
believes its tax positions are supportable and consistent with the applicable
provisions of the Internal Revenue Code. On October 10, 2003, the company issued
a written rebuttal response asserting that the IRS erred in its determinations
and has requested a conference to resolve the proposed disallowance.

NOTE 12 - NEW ACCOUNTING STANDARDS

         SFAS No. 149, "Amendment of Statement 133 on Derivative Instruments and
Hedging Activities," amends and clarifies financial accounting and reporting for
derivative instruments, including certain derivative instruments embedded in
other contracts and for hedging activities under SFAS No. 133, "Accounting for
Derivative Instruments and Hedging Activities." It is effective for contracts
entered into or modified after June 30, 2003, except as stated within the
statement, and should be applied prospectively. The company does not expect this
statement to have a material effect on its financial statements.

                                     - 11 -

<PAGE>

         SFAS No. 150, "Accounting for Certain Financial Instruments with
Characteristics of Both Liabilities and Equity," modifies the traditional
definition of liabilities to encompass certain obligations that must be settled
through the issuance of equity shares. These obligations are considered
liabilities as opposed to equity or mezzanine financing under the provisions of
SFAS No. 150. This statement does not apply to features that are embedded in a
financial instrument that is not a derivative in its entirety. It is effective
for financial instruments entered into or modified after May 31, 2003, and
otherwise effective at the beginning of fiscal 2004. The company does not have
any of the instruments covered by this statement; therefore, this statement is
not expected to have a material effect on its financial statements.

                                     - 12 -
<PAGE>

ITEM 2. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
OF OPERATIONS

RESULTS OF OPERATIONS

OVERALL PERFORMANCE

         Sales of $161,344,000 during the three-month period ended September 30,
2003 (fiscal 2004) were 34.4% higher than $120,082,000 in the first three months
of the prior fiscal year (fiscal 2003). During the three-month period ended
September 30, 2003, net income of $9,137,000 was 1.6% higher than $8,996,000 for
the same period last year. Included in net income in the first quarter of fiscal
2003 was $3,496,000 of benefit, net of tax, from the reversal of noncash stock
option compensation (see note 7 - Noncash Stock Option Compensation). Net income
in the first quarter of fiscal 2004 was 66.1% higher than pro forma income of
$5,500,000 in the year-ago quarter (which excludes the $3,496,000 after tax
stock option compensation benefit in the year-ago quarter). For comparative
purposes, management believes this comparison is appropriate, since the benefit
resulted solely from changes in the company's stock price and not from
operations.

         Consolidated operating income of $16,167,000 in the quarter ended
September 30, 2003 was 1.5% higher than $15,930,000 in the first quarter in the
prior fiscal year. Operating income in the prior year period increased
$5,378,000 as a result of the pretax benefit of the aforementioned noncash stock
option compensation. Consolidated operating income in the first quarter of
fiscal 2004 was 53.2% higher than pro forma consolidated operating income of
$10,552,000 (which excludes the $5,378,000 noncash stock option compensation
benefit in the year-ago quarter). For comparative purposes, management believes
this comparison is appropriate, since the benefit resulted solely from changes
in the company's stock price and not from operations.

         As a percentage of sales, operating income was 10.0% in the first
quarter of fiscal 2004 compared to 13.3% (8.8% on a pro forma basis which
excludes the noncash stock option compensation benefit of 4.5% of sales) for the
same quarter in fiscal 2003. Cost of sales was 79.9% of sales in the first
quarter of fiscal 2004 compared to 79.5% in the prior year period. Higher
asphalt and other raw material costs during the current year period were largely
offset by better shingle pricing and increased shingle production, which reduced
per unit manufacturing costs. Other selling, general and administrative (Other
SG&A) costs in the three-month period ended September 30, 2003 were higher than
in the first quarter of the prior fiscal year, primarily as a result of
increased business activity; however, as a percentage of sales, Other SG&A costs
were 10.1% in the first quarter of fiscal 2004, compared to 11.7% in the same
quarter last year.

         Interest expense, net, was $1,383,000 in the first quarter of fiscal
2004 compared to $1,680,000 in the same prior year period. In the first quarter
of fiscal 2004, interest expense of $576,000 was capitalized related to the
construction of an additional shingle plant in Tuscaloosa, Alabama, and other
significant capital projects. In fiscal 2003, $47,000 of interest was
capitalized.

         The company's effective tax rate was 38.2% during the first quarter of
fiscal 2004 compared to 36.9% for the same period in fiscal 2003. The difference
between years primarily relates to the impact of noncash stock option
compensation benefit on the effective tax rate in fiscal 2003.

                                     - 13 -
<PAGE>

RESULTS OF BUSINESS SEGMENTS

         Sales in the Building Products segment increased 38.9% to $157,367,000
for the three months ended September 30, 2003 compared to $113,316,000 in the
same prior year period. The significant year-to-year increase in sales is
primarily the result of $42,654,000 in higher premium roofing sales. Compared to
the same quarter last year, unit shingle shipments increased 33.8%, with most
regions of the United States of America experiencing strong year-to-year growth.
About one-half of the unit volume increase was attributable to continued strong
roof replacement demand in hail-damaged Texas markets. Average shingle pricing
increased about 5.9% compared to the year-ago quarter. For the three-month
period ended September 30, 2003, external sales of performance nonwoven fabrics
increased $665,000, or 8.0%, compared to the first quarter last year. Sales of
composite building products were $732,000 in the first quarter of fiscal 2004.
During the first quarter of fiscal 2003, the company had not yet entered the
composite wood business.

         Operating income for the Building Products segment of $21,904,000 for
the three-month period ended September 30, 2003 increased 51.1% compared to
$14,498,000 achieved in the first three months of fiscal 2003. Higher operating
income from premium roofing products resulted primarily from higher unit
volumes, combined with an improved relationship between shingle pricing and
asphalt costs.

         Management believes the near-term outlook for the roofing industry is
favorable as a result of strong overall roofing replacement demand, some of
which resulted from calendar 2003 storm damage that will likely extend into the
calendar 2004 roofing season. Market indications are that industry-wide product
inventories have tightened relative to demand. Reflective of these market
conditions, the company implemented a price increase of approximately 1.5%, in
most markets, effective October 1, 2003. Shingle granules in the region
supplying the Myerstown, Pennsylvania roofing plant are in short supply and may
be subject to attempted allocation by the manufacturer. Potential shortages can
be mitigated by shipments of granules from sources in other geographic regions.
Nevertheless, some curtailment of plant utilization at that roofing plant is
possible during this temporary granule shortage.

         Operating income gains attributable to higher premium roofing product
sales were partially offset by an operating loss of approximately $1,100,000 for
the composite wood business during the first quarter of fiscal 2004.
Manufacturing efficiency for the composite wood business improved significantly
during the quarter, but sales were below the break-even level as distribution
channel expansion was strategically curtailed during the quarter pending
sustainable improvement in manufacturing throughput. Management believes
improvements in manufacturing efficiency in the composite wood operation will be
more evident as the composite wood distribution channels are expanded in the
coming months. Operating income from performance nonwoven fabrics was comparable
between years.

         The Other, Technologies companies reported combined sales of $3,977,000
in the first three months of fiscal 2004 compared to $6,766,000 in the same
period in fiscal 2003. Lower sales at Cybershield were largely responsible for
the sales decline as several cellular phone models that previously utilized
Cybershield's traditional shielding and services were discontinued.

                                     - 14 -
<PAGE>

Replacement sales for a portion of this decline are expected as the year
progresses from the sales ramp of recently awarded new projects and from a
growing pipeline of specifically identified new opportunities. During the first
quarter of fiscal 2004, Cybershield began commercial production of new products
based upon the company's proprietary EXACT(TM) precise metallization technology.

         Ortloff recognized no significant license fee income in the three-month
period ended September 30, 2003. One license fee of approximately $500,000 was
signed in mid-October 2003, and several other license fee agreements that were
expected to be signed by September 30, 2003 are expected to be executed later in
fiscal 2004. Chromium's sales were marginally lower in the first quarter of
fiscal 2004 compared to the same period last year. During the current year
quarter, Chromium and the Electro-Motive Division of General Motors (GM EMD)
signed a manufacturer's representation agreement whereby GM EMD will promote and
market Chromium's reciprocating engine components through the extensive GM EMD
sales network in international and specific domestic markets. Elk Technologies
had no significant sales of fire retardant mattress fabrics during the first
quarter of fiscal 2004.

         Other, Technologies companies had a combined operating loss of
$2,063,000 in the three-month period ended September 30, 2003, compared to a
$1,089,000 operating loss in the same period last year. Lower operating results
at Cybershield, primarily due to lower sales, were largely responsible for the
higher current year operating loss. Chromium was modestly profitable in the
first quarter of both fiscal years 2004 and 2003, and Ortloff had a comparable
operating loss of approximately $500,000 in both fiscal year periods.

FINANCIAL CONDITION

         Cash flows from operating activities are generally the result of net
income, deferred taxes, depreciation and amortization, and changes in working
capital. During the first three months of fiscal 2004, the company generated
operating cash flows of $35,445,000 compared to $17,913,000 for the first three
months in fiscal 2003. The increase in cash flows generated in the first quarter
of fiscal 2004 was primarily the result of changing dynamics in the significant
components of working capital compared to the prior fiscal year. Even with
increased sales in the quarter, trade receivables at September 30, 2003 were
$2,791,000 lower than at June 30, 2003, primarily due to the collection of
$6,832,000 of deferred trade receivables from promotional programs to certain
customers in the quarter. Despite operating its roofing plants at a very high
rate in the first quarter of fiscal 2004, inventories at September 30, 2003 were
$14,017,000 lower than at June 30, 2003, primarily due to very strong demand for
premium roofing products during the quarter.

         The current ratio was 3.3 to 1 at September 30, 2003 compared to 3.4 to
1 at June 30, 2003. Historically, working capital requirements fluctuate during
the year because of seasonality in some market areas. Generally, working capital
requirements and related borrowings are higher in the spring and summer months,
and lower in the fall and winter months.

         Cash flows from investing activities primarily reflect the company's
capital expenditure strategy. Net cash used for investing activities was
$17,303,000 in the first three months of fiscal 2004 compared to $8,251,000 in
the same period last year. Approximately $12,500,000 of current year capital
expenditures relate to construction of a second shingle manufacturing plant

                                     - 15 -
<PAGE>

at the Tuscaloosa, Alabama facility, including the installation of certain
infrastructure and material handling improvements designed to enhance the
overall efficiency of the expanded facility. Capital expenditures are projected
to be approximately $69,000,000 in fiscal 2004, including approximately
$43,000,000 (inclusive of the aforementioned $12,500,000 incurred in the first
quarter) to complete the new Tuscaloosa plant, approximately $6,000,000 for
productivity enhancement projects, and approximately $6,000,000 to upgrade
certain key information technology platforms. After fiscal 2004, planned capital
expenditures are currently expected to be approximately $15,000,000 -
$20,000,000 per year.

         Cash flows from financing activities generally reflect changes in the
company's borrowings during the period, together with dividends paid on common
stock, treasury stock transactions and exercises of stock options. Net cash used
for financing activities was $439,000 in the first quarter of fiscal 2004
compared to $950,000 in the same period fiscal 2003. There was no change in the
amount of principal debt outstanding during the first quarter of fiscal 2004.
The decrease in long-term debt during the first quarter of fiscal 2004 was the
result of a $2,034,000 adjustment in the fair value of long-term debt resulting
from an interest rate swap to effectively convert the interest rate from fixed
to floating on $60,000,000 of long-term debt through 2012. This fair market
adjustment to the carrying amount of long-term debt is offset by recording a
corresponding amount in other assets for the value of the interest rate swap
instrument.

         At September 30, 2003, liquidity consisted of $22,759,000 of cash and
cash equivalents and $97,403,000 of available borrowings under the company's
$100,000,000 committed Revolving Credit Facility. The debt to capital ratio
(after deducting cash and cash equivalents from $145,000,000 of principal debt)
was 37.3%. The company has no off-balance sheet arrangements or transactions
with unconsolidated, special purpose entities.

         The company's Board of Directors has authorized the purchase of common
stock from time to time on the open market. As of September 30, 2003, the
company has repurchase authority of approximately $10,600,000 remaining.

         See footnote 10 on pages 10 and 11 of this Form 10-Q for a summary of
the company's environmental risk and footnote 12 on page 11 and 12 for a
discussion of new accounting standards.

         Management believes that current cash and cash equivalents, projected
cash flows from operations, and its existing debt capacity should be sufficient
during fiscal 2004 and beyond to fund the Tuscaloosa, Alabama plant
construction, other planned capital expenditures, working capital needs,
dividends, stock repurchases and other cash requirements.

CRITICAL ACCOUNTING POLICIES

         The company's condensed consolidated financial statements were prepared
in conformity with accounting principles generally accepted in the United States
of America. As such, management is required to make certain estimates, judgments
and assumptions it believes are reasonable based on the information available.
The accounting policies which management believes are the most critical to fully
understanding and evaluating the company's reported financial results are:

                                     - 16 -
<PAGE>

            -  Collectibility of Accounts Receivable

            -  Accruals for Loss Contingencies, including product warranties,
               litigation, environmental exposure and self-insurance reserves

            -  Inventories

            -  Revenue Recognition

            -  Impairment of Long-Lived Assets

         These critical accounting policies are described in Management's
Discussion and Analysis of Financial Condition and Results of Operations on
pages 24 through 26 in the company's Form 10-K for its fiscal year ended June
30, 2003. There were no significant changes in critical accounting policies
during the three-month period ended September 30, 2003.

FORWARD-LOOKING STATEMENTS

         In an effort to give investors a well-rounded view of the company's
current condition and future opportunities, management's discussion and analysis
of the results of operations and financial condition and other sections of this
Form 10-Q contain "forward-looking statements" that involve risks and
uncertainties about its prospects for the future. The statements that are not
historical facts are forward-looking statements within the meaning of the
Private Securities Litigation Reform Act of 1995. These statements usually are
accompanied by words such as "optimistic," "outlook," "believe," "estimate,"
"potential," "project," "expect," "anticipate," "plan," "predict," "could,"
"should," "may," "likely," "possible," or similar words that convey the
uncertainty of future events or outcomes. These statements are based on
judgments the company believes are reasonable; however, actual results could
differ materially from those discussed here. Factors that could cause or
contribute to such differences could include, but are not limited to:

         1.  The company's building products business is substantially
             non-cyclical, but can be affected by weather, the availability of
             financing, insurance claims paying practices, and general economic
             conditions. In addition, the asphalt roofing products manufacturing
             business is highly competitive. Actions of competitors, including
             changes in pricing, or slowing demand for asphalt roofing products
             due to general or industry economic conditions or the amount of
             inclement weather could result in decreased demand for the
             company's products, lower prices received or reduced utilization of
             plant facilities. Further, changes in building and insurance codes
             and other standards from time to time can cause changes in demand,
             or increases in costs that may not be passed through to customers.

         2.  In the building products business, the significant raw materials
             are ceramic-coated granules, asphalt, glass fibers, resins and
             mineral filler. Increased costs of raw materials can result in
             reduced margins, as can higher energy, trucking and rail costs.
             Historically, the company has been able to pass some of the higher
             raw material, energy and transportation costs through to the
             customer. Should the company be unable to recover higher raw
             material, energy and/or transportation costs from price increases
             of its products, operating results could be adversely affected
             and/or lower than projected.

                                     - 17 -

<PAGE>

         3.  Temporary shortages or disruption in supply of raw materials or
             transportation do result from time to time from a variety of
             causes. If the company experiences temporary shortages or
             disruption of supply of raw materials, operating results could be
             adversely affected and/or lower than projected.

         4.  The company has been involved in a significant expansion plan over
             the past several years, including the construction of new
             facilities and the expansion of existing facilities. Progress in
             achieving anticipated operating efficiencies and financial results
             is difficult to predict for new and expanded plant facilities. If
             such progress is slower than anticipated, or if demand for products
             produced at new or expanded plants does not meet current
             expectations, operating results could be adversely affected.

         5.  Certain facilities of the company's subsidiaries must utilize
             hazardous materials in their production process. As a result, the
             company could incur costs for remediation activities at its
             facilities or off-site, and other related exposures from time to
             time in excess of established reserves for such activities.

         6.  The company's litigation is subject to inherent and case-specific
             uncertainty. The outcome of such litigation depends on numerous
             interrelated factors, many of which cannot be predicted.

         7.  Although the company currently anticipates that most of its needs
             for new capital in the near future will be met with internally
             generated funds or borrowings under its available credit
             facilities, significant increases in interest rates could
             substantially affect its borrowing costs or its cost of alternative
             sources of capital.

         8.  Each of the company's businesses, especially Cybershield's
             business, is subject to the risks of technological changes and
             competition that is based on technology improvement or labor
             savings. These factors could affect the demand for or the relative
             cost of the company's technology, products and services, or the
             method and profitability of the method of distribution or delivery
             of such technology, products and services. In addition, the
             company's businesses each could suffer significant setbacks in
             revenues and operating income if it lost one or more of its largest
             customers, or if its customers' plans and/or markets should change
             significantly. Cybershield has lost substantial business as a
             result of most cellular handset production moving to Asia where
             Cybershield has no significant presence. Low labor costs in Asia
             make other coating processes competitive with those Cybershield
             would use. Cybershield's future viability may depend on the
             successful commercialization of the EXACT process, or other value
             added services, which are unproven as yet on a large commercial
             scale.

         9.  Although the company insures itself against physical loss to its
             manufacturing facilities, including business interruption losses,
             natural or other disasters and accidents, including but not limited
             to fire, earthquake, damaging winds, and

                                      - 18 -
<PAGE>

             explosions, operating results could be adversely affected if any of
             its manufacturing facilities became inoperable for an extended
             period of time due to these or other events, including but not
             limited to acts of God, war or terrorism.

         10. Each of the company's businesses is actively involved in the
             development of new products, processes and services which are
             expected to contribute to the company's ongoing long-term growth
             and earnings. Products using VersaShield fire retardant coatings
             have not yet produced significant commercial sales. Its market
             potential may be dependent on the stringency of federal and state
             regulatory requirements, which are difficult to predict. If such
             development activities are not successful, regulatory requirements
             are less stringent than currently predicted, market demand is less
             than expected, or the company cannot provide the requisite
             financial and other resources to successfully commercialize such
             developments, the growth of future sales and earnings may be
             adversely affected.

Parties are cautioned not to rely on any such forward-looking beliefs or
judgments in making investment decisions.

                                     - 19 -
<PAGE>

ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

         In addition to the risks inherent in its operations, the company is
exposed to financial, market, political and economic risks. The following
discussion provides additional detail regarding the company's exposure to the
risks of changing commodity prices and interest rates. The company has no
significant foreign exchange risk. Derivatives are held from time to time only
as part of a formally documented risk management program. Derivatives are held
to mitigate uncertainty, volatility or to cover underlying exposures. No
derivatives are held for trading purposes. The company has entered into
derivative transactions related to interest rate risk and its exposure to
natural gas used in its manufacturing plants, as summarized in the following
paragraphs.

         The company is required to purchase natural gas for use in its
manufacturing facilities. These purchases expose the company to the risk of
higher natural gas prices. There are no natural gas hedge transactions in effect
at September 30, 2003. However, it is anticipated that hedging strategies will
likely be utilized in the future to limit the company's exposure to volatility
in the price of natural gas used in its manufacturing plants.

         The company uses interest rate swaps to help maintain a reasonable
balance between fixed and floating rate debt. The company has entered into an
interest rate swap to effectively convert the interest rate from fixed to
floating on $60,000,000 of its outstanding debt at September 30, 2003. The fair
value of this swap was $5,492,000 at September 30, 2003. Based on outstanding
debt at September 30, 2003, the company's interest costs would increase or
decrease $600,000 for each theoretical 1% increase or decrease in the floating
interest rate.

ITEM 4. CONTROLS AND PROCEDURES

     a)  Evaluation of Disclosure Controls and Procedures

         The company completed an evaluation, under the supervision and with the
         participation of management, including the Chief Executive Officer and
         Chief Financial Officer, of the effectiveness of the design and
         operation of the company's disclosure controls and procedures pursuant
         to Exchange Act Rule 13a-15 as of the end of the period covered by this
         report. Based upon that evaluation, the Chief Executive Officer and the
         Chief Financial Officer concluded that the company's disclosure
         controls and procedures are effective to timely alert them to any
         material information relating to the company (including its
         consolidated subsidiaries) that must be included in the company's
         periodic SEC filings.

     b)  Changes in Internal Control

         In connection with the evaluation described above, we identified no
         change in our internal control over financial reporting that occurred
         during our fiscal quarter ended September 30, 2003 and that has
         materially affected, or is reasonably likely to materially affect, our
         internal control over financial reporting.

                                     - 20 -
<PAGE>

PART II. OTHER INFORMATION

ITEM 6: EXHIBITS AND REPORTS ON FORM 8-K

         (a)      Exhibits:

                  31.1     Certification of Chief Executive Officer Pursuant to
                           Section 302 of the Sarbanes-Oxley Act of 2002.

                  31.2     Certification of Chief Financial Officer Pursuant to
                           Section 302 of the Sarbanes-Oxley Act of 2002.

                  32.1     Certificate of the Chief Executive Officer of ElkCorp
                           Pursuant to Section 906 of the Sarbanes-Oxley Act of
                           2002

                  32.2     Certificate of the Chief Financial Officer of ElkCorp
                           Pursuant to Section 906 of the Sarbanes-Oxley Act of
                           2002

         (b)      The company filed two reports on Form 8-K during the quarter
                  ended September 30, 2003. The company filed a Form 8-K on July
                  18, 2003 relating to a press release containing preliminary
                  earnings estimates for the fiscal 2003 fourth quarter,
                  including "forward-looking" statements about its prospects for
                  the future. The company filed a Form 8-K on August 14, 2003
                  relating to a press release containing fiscal 2003 fourth
                  quarter operating results, including "forward-looking"
                  statements about its prospects for the future.

                                     - 21 -
<PAGE>

                                   SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the company
has duly caused this report to be signed on its behalf by the undersigned
thereunto duly authorized.

                                           ElkCorp

DATE: November 4, 2003                     /s/ Harold R. Beattie, Jr.
                                           -------------------------------------
                                           Harold R. Beattie, Jr.
                                           Senior Vice President,
                                           Chief Financial Officer and Treasurer

                                           /s/ Leonard R. Harral
                                           -------------------------------------
                                           Leonard R. Harral
                                           Vice President and Chief
                                           Accounting Officer

                                     - 22 -
<PAGE>
                               INDEX TO EXHIBITS

<Table>
<Caption>
                 Exhibit
                 Number                     Description
                ---------                   -----------
<S>                        <C>
                  31.1     Certification of Chief Executive Officer Pursuant to
                           Section 302 of the Sarbanes-Oxley Act of 2002.

                  31.2     Certification of Chief Financial Officer Pursuant to
                           Section 302 of the Sarbanes-Oxley Act of 2002.

                  32.1     Certificate of the Chief Executive Officer of ElkCorp
                           Pursuant to Section 906 of the Sarbanes-Oxley Act of
                           2002

                  32.2     Certificate of the Chief Financial Officer of ElkCorp
                           Pursuant to Section 906 of the Sarbanes-Oxley Act of
                           2002
</Table>