Document Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 01, 2019
Document Entity Information
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
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
Is Entity's Reporting Status Current?	Yes
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		5,134,492