<?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>0001215540</rptOwnerCik>
            <rptOwnerName>POMPA MARK A</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>SVP, CAO &amp; Treasurer</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>1928</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>42.53</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>23872</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 12,900 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>Mark A. Pompa</signatureName>
        <signatureDate>2006-02-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2006-02-24
0000105634
EMCOR GROUP INC
EME
0001215540
POMPA MARK A
301 MERRITT SEVEN
NORWALK
CT
06851
0
1
0
0
SVP, CAO & Treasurer
Common Stock
2006-02-24
4
F
0
1928
42.53
D
23872
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 12,900 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.
Mark A. Pompa
2006-02-27