Exhibit 23.1 CONSENT OF INDEPENDENT AUDITORS We consent to the incorporation by reference in the Registration Statement (Form S-8) pertaining to the: Oldcastle Architectural, Inc. Union Employees 401(k) Plan Pike Industries, Inc. Profit Sharing and Deferred Income Plan Oldcastle Southwest 401(k) Retirement Plan Hallett Construction Company 401(k) Plan Pennsy Supply, Inc. 401(k) and Profit Sharing Plan CPM Development Corporation Profit Sharing Retirement Plan and to the incorporation by reference therein of our report, dated March 4, 2002, except as to Note 33 as to which the date is June 14, 2002, with respect to the consolidated financial statements and schedule of CRH plc included in its Annual Report (Form 20-F) for the year ended December 31, 2001, filed with the Securities and Exchange Commission. Yours faithfully /s/ Ernst & Young - --------------------------------------------- Ernst & Young Dublin, Ireland March 3, 2003