Document Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 01, 2020
Document Entity Information
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
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		5,183,991
Entity Interactive Data Current	Yes
Entity Incorporation State Country Code	DE
Entity File Number	1-13752