EXHIBIT 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with this Quarterly Report on Form 10-Q of Limbach Holdings, Inc. (the “Company”) for the quarter ended March 31, 2024 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), the undersigned Michael M. McCann, the President and Chief Executive Officer of the Company, hereby certifies, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that, to the best of the undersigned’s knowledge and belief:

(1)the Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and

(2)the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date: May 8, 2024
By	/s/ Michael M. McCann
Michael M. McCann, President and Chief Executive Officer
(Principal Executive Officer)