Equity	6 Months Ended
Jun. 30, 2020
Stockholders' Equity Note [Abstract]
Equity	Equity The Company’s second amended and restated certificate of incorporation currently authorizes the issuance of 100,000,000 shares of common stock, par value $0.0001, and 1,000,000 shares of preferred stock, par value $0.0001. At June 30, 2020 and December 31, 2019, the Company had outstanding warrants exercisable for 4,576,799 shares of common stock, consisting of: (i) 4,600,000 warrants issued as part of units in its initial public offering, each of which is exercisable for one-half of one share of common stock at an exercise price of $11.50 per whole share (“Public Warrants”); (ii) 198,000 warrants, each exercisable for one-half of one share of common stock at an exercise price of $5.75 per half share ($11.50 per whole share) (“Sponsor Warrants”); (iii) 600,000 warrants, each exercisable for one share of common stock at an exercise price of $15.00 per share (“$15 Exercise Price Warrants”); (iv) 631,119 warrants, each exercisable for one share of common stock at an exercise price of $12.50 per share (“Merger Warrants”); and (v) 946,680 warrants, each exercisable for one share of common stock at an exercise price of $11.50 per share (“Additional Merger Warrants”). The Public Warrants, Sponsor Warrants and $15 Exercise Price Warrants were issued under a warrant agreement dated July 15, 2014, between Continental Stock Transfer & Trust Company, as warrant agent, and the Company. The Merger Warrants and Additional Merger Warrants were issued to the sellers of LHLLC. On July 21, 2014, a total of 300,000 Unit Purchase Options (“UPOs”) were issued by 1347 Capital to a representative of the underwriter and its designees. The 17,100 UPOs that were outstanding at June 30, 2019 expired on July 21, 2019. Each UPO consisted of one share of common stock, one right to purchase one-tenth of one share of common stock and one warrant to purchase one-half of one share of common stock at an exercise price of $11.50 per full share, exercisable on a cash or cashless basis. In 2020, the Compensation Committee of the Board of Directors of the Company granted 118,633 restricted stock units (“RSUs”) and 96,500 performance-based RSUs (“PRSUs”) under the Limbach Holdings, Inc. Omnibus Incentive Plan (as amended, the “Omnibus Incentive Plan”) to certain executive officers, non-executive employees and non-employee directors of the Company in the form of an annual ongoing long-term incentive RSU award (the “2020 Ongoing LTI RSU Award”), and an ongoing RSU award to non-employee directors (“2020 Ongoing Director RSU Award”). The 2020 Ongoing LTI RSU Award and 2020 Ongoing Director RSU Award only contains service-based awards. On May 24, 2020 the Board of Directors approved further amendments to the Company's amended and restated Omnibus Incentive Plan to increase the number of shares of the Company's common stock that may be issued pursuant to awards by 500,000, for a total of 1,650,000 shares, and extend the term of the plan so that it will expire on the tenth anniversary of the date the stockholders approve the Amended Incentive Plan. The amendments were approved by the Company's stockholders at the Annual Meeting held on July 14, 2020. See Note 17 - Management Incentive Plans for RSUs granted, vested, forfeited and remaining unvested and Note 18 - Subsequent Events. Upon approval of the Company's stockholders on May 30, 2019, the Company adopted the Limbach Holdings, Inc. 2019 Employee Stock Purchase Plan (“the ESPP”). On January 1, 2020, the ESPP went into effect. The ESPP enables eligible employees, as defined by the ESPP, the right to purchase the Company's common stock through payroll deductions during consecutive subscription periods at a purchase price of 85% of the fair market value of a common share at the end of each offering period. Annual purchases by participants are limited to the number of whole shares that can be purchased by an amount equal to ten percent of the participant's compensation or $5,000, whichever is less. Each offering period of the ESPP lasts six months, commencing on January 1 and July 1 of each year. The amounts collected from participants during a subscription period are used on the exercise date to purchase full shares of common stock. Participants may withdraw from an offering before the exercise date and obtain a refund of amounts withheld through payroll deductions. Compensation cost, representing the 15% discount applied to the fair market value of common stock, is recognized on a straight-line basis over the six-month vesting period during which employees perform related services. Under the ESPP 500,000 shares are authorized to be issued. As of June 30, 2020, no shares have been issued under the ESPP.

Equity

The Company’s second amended and restated certificate of incorporation currently authorizes the issuance of 100,000,000 shares of common stock, par value $0.0001, and 1,000,000 shares of preferred stock, par value $0.0001.

At June 30, 2020 and December 31, 2019, the Company had outstanding warrants exercisable for 4,576,799 shares of common stock, consisting of: (i) 4,600,000 warrants issued as part of units in its initial public offering, each of which is exercisable for one-half of one share of common stock at an exercise price of $11.50 per whole share (“Public Warrants”); (ii) 198,000 warrants, each exercisable for one-half of one share of common stock at an exercise price of $5.75 per half share ($11.50 per whole share) (“Sponsor Warrants”); (iii) 600,000 warrants, each exercisable for one share of common stock at an exercise price of $15.00 per share (“$15 Exercise Price Warrants”); (iv) 631,119 warrants, each exercisable for one share of common stock at an exercise price of $12.50 per share (“Merger Warrants”); and (v) 946,680 warrants, each exercisable for one share of common stock at an exercise price of $11.50 per share (“Additional Merger Warrants”). The Public Warrants, Sponsor Warrants and $15 Exercise Price Warrants were issued under a warrant agreement dated July 15, 2014, between Continental Stock Transfer & Trust Company, as warrant agent, and the Company. The Merger Warrants and Additional Merger Warrants were issued to the sellers of LHLLC.

On July 21, 2014, a total of 300,000 Unit Purchase Options (“UPOs”) were issued by 1347 Capital to a representative of the underwriter and its designees. The 17,100 UPOs that were outstanding at June 30, 2019 expired on July 21, 2019. Each UPO consisted of one share of common stock, one right to purchase one-tenth of one share of common stock and one warrant to purchase one-half of one share of common stock at an exercise price of $11.50 per full share, exercisable on a cash or cashless basis.

In 2020, the Compensation Committee of the Board of Directors of the Company granted 118,633 restricted stock units (“RSUs”) and 96,500 performance-based RSUs (“PRSUs”) under the Limbach Holdings, Inc. Omnibus Incentive Plan (as amended, the “Omnibus Incentive Plan”) to certain executive officers, non-executive employees and non-employee directors of the Company in the form of an annual ongoing long-term incentive RSU award (the “2020 Ongoing LTI RSU Award”), and an ongoing RSU award to non-employee directors (“2020 Ongoing Director RSU Award”). The 2020 Ongoing LTI RSU Award and 2020 Ongoing Director RSU Award only contains service-based awards.

On May 24, 2020 the Board of Directors approved further amendments to the Company's amended and restated Omnibus Incentive Plan to increase the number of shares of the Company's common stock that may be issued pursuant to awards by 500,000, for a total of 1,650,000 shares, and extend the term of the plan so that it will expire on the tenth anniversary of the date the stockholders approve the Amended Incentive Plan. The amendments were approved by the Company's stockholders at the Annual Meeting held on July 14, 2020.

See Note 17 - Management Incentive Plans for RSUs granted, vested, forfeited and remaining unvested and Note 18 - Subsequent Events.

Upon approval of the Company's stockholders on May 30, 2019, the Company adopted the Limbach Holdings, Inc. 2019 Employee Stock Purchase Plan (“the ESPP”). On January 1, 2020, the ESPP went into effect. The ESPP enables eligible employees, as defined by the ESPP, the right to purchase the Company's common stock through payroll deductions during consecutive subscription periods at a purchase price of 85% of the fair market value of a common share at the end of each offering period. Annual purchases by participants are limited to the number of whole shares that can be purchased by an amount equal to ten percent of the participant's compensation or $5,000, whichever is less. Each offering period of the ESPP lasts six months, commencing on January 1 and July 1 of each year. The amounts collected from participants during a subscription period are used on the exercise date to purchase full shares of common stock. Participants may withdraw from an offering before the exercise date and obtain a refund of amounts withheld through payroll deductions. Compensation cost, representing the 15% discount applied to the fair market value of common stock, is recognized on a straight-line basis over the six-month vesting period during which employees perform related services. Under the ESPP 500,000 shares are authorized to be issued. As of June 30, 2020, no shares have been issued under the ESPP.