Document Entity Information	9 Months Ended
	Sep. 30, 2012	Nov. 07, 2012
Entity Information [Line Items]
Entity Registrant Name	SMITH MIDLAND CORP
Entity Central Index Key	0000924719
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Document Type	10-Q
Document Period End Date	Sep. 30, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		4,785,262
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes