<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-11-22</periodOfReport>

    <issuer>
        <issuerCik>0000102729</issuerCik>
        <issuerName>VALMONT INDUSTRIES INC</issuerName>
        <issuerTradingSymbol>VMI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001185232</rptOwnerCik>
            <rptOwnerName>BAY MOGENS C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>VALMONT INDUSTRIES, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>ONE VALMONT PLAZA</rptOwnerStreet2>
            <rptOwnerCity>OMAHA</rptOwnerCity>
            <rptOwnerState>NE</rptOwnerState>
            <rptOwnerZipCode>68154</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chairman and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-11-22</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>G</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>240000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes></footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ R. Andrew Massey for Mogens C Bay</signatureName>
        <signatureDate>2017-11-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2017-11-22
0000102729
VALMONT INDUSTRIES INC
VMI
0001185232
BAY MOGENS C
VALMONT INDUSTRIES, INC.
ONE VALMONT PLAZA
OMAHA
NE
68154
1
1
0
0
Chairman and CEO
Common Stock
2017-11-22
5
G
0
10000
0
D
240000
D
/s/ R. Andrew Massey for Mogens C Bay
2017-11-27