Document Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Mar. 05, 2020	Jun. 30, 2019
Document Entity Information
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Registrant Name	SMITH MIDLAND CORP
Entity Central Index Key	0000924719
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Shell Company	false
Is Entity a Well-known Seasoned Issuer?	No
Is Entity a Voluntary Filer?	No
Is Entity's Reporting Status Current?	Yes
Entity Interactive Data Current	Yes
Entity Incorporation, State or Country Code	DE
Entity File Number	1-13752
Entity Common Stock, Shares Outstanding		5,164,685
Entity Public Float			$ 30,748,256