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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-06-01</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001451762</rptOwnerCik>
            <rptOwnerName>Laidley David H.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>359 METCALFE AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WESTMOUNT</rptOwnerCity>
            <rptOwnerState>A8</rptOwnerState>
            <rptOwnerZipCode>H3Z 2J2</rptOwnerZipCode>
            <rptOwnerStateDescription>QUEBEC, CANADA</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>2017-06-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2790</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>67759</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The shares reported herein as acquired represents shares of common stock issuable in the future with respect to restricted stock units (&quot;RSU's&quot;) granted to the reporting person.</footnote>
        <footnote id="F2">Includes shares issuable in respect of RSU's.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>By Maxine L. Mauricio, Attorney-in-Fact</signatureName>
        <signatureDate>2017-06-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2017-06-01
0000105634
EMCOR GROUP INC
EME
0001451762
Laidley David H.
359 METCALFE AVENUE
WESTMOUNT
A8
H3Z 2J2
QUEBEC, CANADA
1
0
0
0
Common Stock
2017-06-01
4
A
0
2790
0
A
67759
D
The shares reported herein as acquired represents shares of common stock issuable in the future with respect to restricted stock units ("RSU's") granted to the reporting person.
Includes shares issuable in respect of RSU's.
By Maxine L. Mauricio, Attorney-in-Fact
2017-06-02