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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-02-24</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001215542</rptOwnerCik>
            <rptOwnerName>CAMMAKER SHELDON I</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>EVP, Gen Counsel &amp; Secretary</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-02-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3440</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>42.53</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>33690</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">These shares were applied by the Company to satisfy withholding tax requirements which arose by reason of shares being issued to the reporting person in respect of certain restricted stock units heretofore granted to him.  The number of shares represents an adjustment required by the 2-for-1 stock split of the Company's common stock effected February 10, 2006 (the &quot;Stock Split&quot;).</footnote>
        <footnote id="F2">Due to the Stock Split, the reporting person's ownership has been adjusted to include 18,565 additional shares of common stock.  This number also includes shares issuable in respect of restricted stock units granted pursuant to the Company's Executive Stock Bonus Plan.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Sheldon I. Cammaker</signatureName>
        <signatureDate>2006-02-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2006-02-24
0000105634
EMCOR GROUP INC
EME
0001215542
CAMMAKER SHELDON I
301 MERRITT SEVEN
NORWALK
CT
06851
0
1
0
0
EVP, Gen Counsel & Secretary
Common Stock
2006-02-24
4
F
0
3440
42.53
D
33690
D
These shares were applied by the Company to satisfy withholding tax requirements which arose by reason of shares being issued to the reporting person in respect of certain restricted stock units heretofore granted to him.  The number of shares represents an adjustment required by the 2-for-1 stock split of the Company's common stock effected February 10, 2006 (the "Stock Split").
Due to the Stock Split, the reporting person's ownership has been adjusted to include 18,565 additional shares of common stock.  This number also includes shares issuable in respect of restricted stock units granted pursuant to the Company's Executive Stock Bonus Plan.
Sheldon I. Cammaker
2006-02-27