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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-04-03</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>Vice Chairman</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-04-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>15284</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>53598</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-04-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5095</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>58693</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 disposed represented shares of common stock issuable in the future in respect to restricted stock units (&quot;RSUs&quot;) granted under the Company's Long Term Incentive Plan.  Such RSUs were surrendered to the Company pursuant to the terms of an agreement dated April 3, 2006 between the reporting person and the Company, all reported in the Company's Form 8-K filed on April 4, 2006 (the &quot;Form 8-K&quot;).</footnote>
        <footnote id="F2">The common stock reported herein as acquired represents shares of common stock issuable in the future in respect of RSUs granted under the Company's 2003 Management Stock Incentive Plan as reported in the Form 8-K.</footnote>
        <footnote id="F3">Includes shares issuable in respect of RSUs.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Leicle E. Chesser</signatureName>
        <signatureDate>2006-04-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2006-04-03
0000105634
EMCOR GROUP INC
EME
0001215544
CHESSER LEICLE E
301 MERRITT SEVEN
NORWALK
CT
06851
0
1
0
0
Vice Chairman
Common Stock
2006-04-03
4
D
0
15284
0
D
53598
D
Common Stock
2006-04-03
4
A
0
5095
0
A
58693
D
The common stock reported herein as disposed represented shares of common stock issuable in the future in respect to restricted stock units ("RSUs") granted under the Company's Long Term Incentive Plan.  Such RSUs were surrendered to the Company pursuant to the terms of an agreement dated April 3, 2006 between the reporting person and the Company, all reported in the Company's Form 8-K filed on April 4, 2006 (the "Form 8-K").
The common stock reported herein as acquired represents shares of common stock issuable in the future in respect of RSUs granted under the Company's 2003 Management Stock Incentive Plan as reported in the Form 8-K.
Includes shares issuable in respect of RSUs.
Leicle E. Chesser
2006-04-03