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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-07-27</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000103973</issuerCik>
        <issuerName>VULCAN MATERIALS CO</issuerName>
        <issuerTradingSymbol>VMC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001185332</rptOwnerCik>
            <rptOwnerName>FRANKLIN H ALLEN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>270 PEACHTREE STREET, NW</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ATLANTA</rptOwnerCity>
            <rptOwnerState>GA</rptOwnerState>
            <rptOwnerZipCode>30303</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock (Deferred Compensation)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-07-27</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>32.555</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>46.076</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>32.555</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4201.72</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Convertible on a 1-for-1 basis.</footnote>
        <footnote id="F2">Director's fees credited to the reporting person's account in accordance with the Vulcan Materials Company Directors' Deferred Compensation Plan.</footnote>
        <footnote id="F3">The units are to be settled in Vulcan common stock commencing at the retirement of the reporting person.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Amy M. Tucker</signatureName>
        <signatureDate>2004-07-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2004-07-27
0
0000103973
VULCAN MATERIALS CO
VMC
0001185332
FRANKLIN H ALLEN
270 PEACHTREE STREET, NW
ATLANTA
GA
30303
1
0
0
0
Phantom Stock (Deferred Compensation)
0
2004-07-27
4
A
0
32.555
46.076
A
Common Stock
32.555
4201.72
D
Convertible on a 1-for-1 basis.
Director's fees credited to the reporting person's account in accordance with the Vulcan Materials Company Directors' Deferred Compensation Plan.
The units are to be settled in Vulcan common stock commencing at the retirement of the reporting person.
Amy M. Tucker
2004-07-29