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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-03-03</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001215544</rptOwnerCik>
            <rptOwnerName>CHESSER LEICLE E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>301 MERRITT SEVEN</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NORWALK</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06851</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive VP and CFO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-03-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3417</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>40.97</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25035</value>
                    <footnoteId id="F2"/>
                </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 Plan which required the reporting person to accept a portion of his 2004 bonus in RSUs and permitted the reporting person to accept a portion of his 2004 bonus in RSUs.</footnote>
        <footnote id="F2">Includes shares issuable in respect of RSUs.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Leicle E. Chesser</signatureName>
        <signatureDate>2005-03-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2005-03-03
0000105634
EMCOR GROUP INC
EME
0001215544
CHESSER LEICLE E
301 MERRITT SEVEN
NORWALK
CT
06851
0
1
0
0
Executive VP and CFO
Common Stock
2005-03-03
4
A
0
3417
40.97
D
25035
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 Plan which required the reporting person to accept a portion of his 2004 bonus in RSUs and permitted the reporting person to accept a portion of his 2004 bonus in RSUs.
Includes shares issuable in respect of RSUs.
Leicle E. Chesser
2005-03-04