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

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-03-03</periodOfReport>

    <issuer>
        <issuerCik>0000105634</issuerCik>
        <issuerName>EMCOR GROUP INC</issuerName>
        <issuerTradingSymbol>EME</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001160599</rptOwnerCik>
            <rptOwnerName>MACINNIS FRANK T</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>301 MERRITT SEVEN</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NORWALK</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06851</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chairman &amp; CEO &amp; President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2004-03-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>6216</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>37.85</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>64695</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The common stock reported herein as acquired represents shares of common stock issuable in the future in respect of restricted stock units (&quot;RSUs&quot;) granted pursuant to the Company Executive Stock Bonus Plan which required the reporting person to accept a portion of his 2003 bonus in RSUs and permitted the reporting person to accept a portion of his 2003 bonus in RSUs.</footnote>
        <footnote id="F2">Of these shares, 3,108 were required to be accepted by the reporting person as part of his 2003 bonus and 3,108 were voluntarily accepted by the reporting person as part of his 2003 bonus.</footnote>
        <footnote id="F3">Includes shares issuable in respect of RSUs.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Frank T. MacInnis</signatureName>
        <signatureDate>2004-03-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0201
4
2004-03-03
0000105634
EMCOR GROUP INC
EME
0001160599
MACINNIS FRANK T
301 MERRITT SEVEN
NORWALK
CT
06851
1
1
0
0
Chairman & CEO & President
Common Stock
2004-03-03
4
A
0
6216
37.85
A
64695
D
The common stock reported herein as acquired represents shares of common stock issuable in the future in respect of restricted stock units ("RSUs") granted pursuant to the Company Executive Stock Bonus Plan which required the reporting person to accept a portion of his 2003 bonus in RSUs and permitted the reporting person to accept a portion of his 2003 bonus in RSUs.
Of these shares, 3,108 were required to be accepted by the reporting person as part of his 2003 bonus and 3,108 were voluntarily accepted by the reporting person as part of his 2003 bonus.
Includes shares issuable in respect of RSUs.
Frank T. MacInnis
2004-03-05