April 17, 2006

Dear Class 6 Creditor:

     Currently pending before the United States Bankruptcy Court for the District of Delaware (the "Bankruptcy Court") is the First Amended Joint Plan of Reorganization of USG Corporation and Its Debtor Subsidiaries (as modified, the "Plan"). Capitalized terms used herein without definition have the meanings provided in the Plan, which is included in the CD-ROM in the package that contains this letter.

     A hearing to consider confirmation of the Plan (the "Confirmation Hearing") has been scheduled for June 15, 2006 at 9:00 a.m., to be continued on June 16, 2006, if necessary. The Plan will not become effective until after the Bankruptcy Court signs an order confirming the Plan and all conditions precedent to the Plan's effectiveness --- including certain actions that must be taken by the District Court - have been either satisfied or waived. No assurance can be given that the conditions precedent to effectiveness of the Plan (including the actions of the District Court) will be satisfied or waived or that the transactions contemplated by the Plan will ultimately be consummated. However, assuming that there are no unexpected delays in either the Bankruptcy Court's or the District Court's action, it is possible that the Debtors could emerge from chapter 11 during the third quarter of 2006. On the assumption that the Plan will be confirmed and become effective within the expected timeframe, the Debtors are preparing to make the distributions called for under the Plan. Those distributions include the cash payments to be made to holders of Allowed Class 6 Claims under the Plan.

     Our records indicate that you are a holder of a Class 6 Claim under the Plan. Accordingly, if and when the Plan becomes effective, and if your Class 6 Claim is allowed, you will be entitle to a cash distribution as provided for under the Plan. However, under the United States federal income tax laws, your distribution may be subject to backup withholding (currently at a rate of 28%) unless you provide the Debtors' claim agent, Logan & Company, Inc. ("Logan & Company"), with your correct taxpayer identification number and certify under penalties of perjury that your are not subject to backup withholding. You may do so by completing the enclosed Form W-9 and returning it to Logan & Company. In general, if you are an individual, your taxpayer identification number is your social security number. Please refer to the enclosed "Guidelines for Certification of Taxpayer Identification Number on Form W-9" for additional instructions regarding completion of this form.

     Certain holders of Claims (including, among others, corporations and certain foreign persons) are not subject to the backup withholding requirements described above. If you are a foreign person that qualifies as an exempt recipient, you must provide Logan & Company with a statement, signed under penalties of perjury, certifying your foreign status, on an appropriate completed IRS Form W-8 (Form W-8BEN, Form W-8ECI, Form W-8EXP or Form W-8IMY). You should consult your tax advisor to determine whether you should complete an IRS Form W-8 and which IRS Form W-8 you should complete. A copy of IRS Form W-8BEN, W-8ECI, Form W-8EXP or Form W-8IMY may be obtained from Logan & Company upon request or at the IRS website (www.irs.gov).

     If you are an exempt recipient (other than an exempt foreign person, who must provide an appropriate completed IRS Form W-8 as discussed above), you are still required to complete the Form W-9 and send it to Logan & Company (including your exempt status and providing your taxpayer identification number) in order to avoid backup withholding.

     If you fail to provide Logan & Company with a validly completed Form W-9 or, where appropriate, IRS Form W-8, your cash distribution will be subject to backup withholding or withheld pending receipt of such forms. Backup withholding is not an additional federal income tax. Rather, the federal income tax liability of a person subject to backup withholding will be reduced by the amount of tax withheld. If withholding results in an overpayment of taxes, a refund may be obtained from the IRS provided that the required information is furnished to the IRS.

     TO AVOID DELAY IN YOUR RECEIPT OF YOUR DISTRIBUTION OR A WITHHOLDING FROM YOUR DISTRIBUTION IF AND WHEN THE PLAN IS CONFIRMED AND BECOMES EFFECTIVE AND YOUR CLAIM IS ALLOWED, PLEASE IMMEDIATELY COMPLETE AND RETURN THE FORM W-9 OR OTHER APPROPRIATE IRS FORM TO LOGAN & COMPANY. YOUR DISTRIBUTION WILL BE SUBJECT TO BACKUP WITHHOLDING OR WITHHELD PENDING LOGAN & COMPANY'S RECEIPT OF A PROPERLY COMPLETED FORM W-9 OR OTHER APPROPRIATE IRS FORM FROM YOU.

     Your receipt of this document does not indicate that your Class 6 Claim is currently an Allowed Claim. If your Class 6 Claim is not an Allowed Claim as of the distribution date, you will not become entitled to a distribution until such time as your Class 6 Claim becomes an Allowed Claim. You should nevertheless complete and return the Form W-9 or the appropriate IRS form to Logan & Company so that your distribution can be delivered if and when your Class 6 Claim becomes an Allowed Claim.

     Completed, SIGNED and dated forms should be mailed in the self-addressed, postage prepaid envelope as soon as possible to:

Logan & Company, Inc.
USG TIN Solicitation
546 Valley Road
Upper Montclair, NJ 07043