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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-07-31</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001113702</rptOwnerCik>
            <rptOwnerName>YONKER MICHAEL T</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>447 GOLDEN EYE DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOCA GRANDE</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>33921</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2018-07-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>27</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>50406</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents restricted stock units (&quot;RSUs&quot;) issued in respect of already outstanding RSUs as a consequence of a dividend paid on the Company's common stock on July 31, 2018.  The RSUs issued on July 31, 2018 are subject to the same vesting and forfeiture provisions as the RSUs in respect of which they have been issued.</footnote>
        <footnote id="F2">Includes shares issuable in respect of RSUs.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>By Maxine L. Mauricio, Attorney-in-Fact</signatureName>
        <signatureDate>2018-08-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2018-07-31
0000105634
EMCOR GROUP INC
EME
0001113702
YONKER MICHAEL T
447 GOLDEN EYE DRIVE
BOCA GRANDE
FL
33921
1
0
0
0
Common Stock
2018-07-31
4
A
0
27
0
A
50406
D
Represents restricted stock units ("RSUs") issued in respect of already outstanding RSUs as a consequence of a dividend paid on the Company's common stock on July 31, 2018.  The RSUs issued on July 31, 2018 are subject to the same vesting and forfeiture provisions as the RSUs in respect of which they have been issued.
Includes shares issuable in respect of RSUs.
By Maxine L. Mauricio, Attorney-in-Fact
2018-08-01