Exhibit 5.1


                  SCHELL BRAY AYCOCK ABEL & LIVINGSTON PLLC
                          SUITE 1500 RENAISSANCE PLAZA
                              230 NORTH ELM STREET
                        GREENSBORO, NORTH CAROLINA 27401



                                   May 1, 2006








FNB United Corp.
101 Sunset Avenue
Asheboro, North Carolina 27203

Re:  325,763  shares of Common Stock,  par value $2.50 per share,  of FNB United
     Corp. offered in connection with the Integrity  Financial  Corporation 1996
     Incentive   Stock  Option  Plan,  as  amended,   the  Integrity   Financial
     Corporation  1997  Nonqualified  Stock Option Plan,  the FGB 1999 Incentive
     Stock Option Plan, the FGB 1999 Nonstatutory  Stock Option Plan and the FGB
     Stock Option Plan

Ladies and Gentlemen:

         We have acted as counsel for FNB United Corp. a North Carolina
corporation (the "Corporation"), in connection with the filing of a registration
statement on Form S-8 under the Securities Act of 1933, as amended (the
"Registration Statement") with respect to 325,763 shares of the Corporation's
common stock, par value $2.50 per share (the "Shares"), to be issued to
participants in the Integrity Financial Corporation 1996 Incentive Stock Option
Plan, as amended, the Integrity Financial Corporation 1997 Nonqualified Stock
Option Plan, the FGB 1999 Incentive Stock Option Plan, the FGB 1999 Nonstatutory
Stock Option Plan and the FGB Stock Option Plan (collectively, the "Plan"). The
options granted and outstanding under the Plan were assumed by the Corporation
pursuant to the Agreement and Plan of Merger dated as of September 18, 2005 by
and between the Corporation and Integrity Financial Corporation.

         We have examined such documents, records and matters of law as we have
deemed necessary for purposes of rendering this opinion. For purposes of this
opinion we have assumed the genuineness of all signatures, the authenticity of
all documents submitted to us as originals, the conformity to originals of all
documents submitted to us as certified, photostatic or conformed copies, and the
authenticity of the originals of such documents.

FNB United Corp.
May 1, 2006
Page two


         We are qualified to practice law in the State of North Carolina. We do
not purport to express any opinion herein concerning any law other than the laws
of the State of North Carolina and the federal securities laws of the United
States.

         Based upon the foregoing, we are of the opinion that the Shares that
may be issued and sold by the Corporation pursuant to the Plan (and the
authorized forms of stock option agreements thereunder) are duly authorized and
will be, when issued and sold in accordance with such Plan and agreements,
validly issued, fully paid and nonassessable.

         We hereby consent to the filing of this opinion as Exhibit 5.1 to the
Registration Statement.

                                  Very truly yours,


                                  /s/ Schell Bray Aycock Abel & Livingston PLLC