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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2026-02-22</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001503564</rptOwnerCik>
            <rptOwnerName>Maass Paul T</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O LAMB WESTON HOLDINGS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>599 S. RIVERSHORE LANE</rptOwnerStreet2>
            <rptOwnerCity>EAGLE</rptOwnerCity>
            <rptOwnerState>ID</rptOwnerState>
            <rptOwnerZipCode>83616</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <remarks>POA filed herewith as Exhibit 24.</remarks>

    <ownerSignature>
        <signatureName>/s/ R. Andrew Massey for Paul T. Maass</signatureName>
        <signatureDate>2026-02-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
