Document and Entity Information - USD ($)	12 Months Ended
	Dec. 30, 2017	Jul. 01, 2017	Feb. 21, 2017
Document and Entity Information
Entity Registrant Name	VALMONT INDUSTRIES INC
Entity Central Index Key	0000102729
Document Type	10-K
Document Period End Date	Dec. 30, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-30
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float		$ 3,296,971,119
Entity Common Stock, Shares Outstanding			22,693,416
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY