<SEC-DOCUMENT>0000352825-25-000032.txt : 20250224
<SEC-HEADER>0000352825-25-000032.hdr.sgml : 20250224
<ACCEPTANCE-DATETIME>20250224172239
ACCESSION NUMBER:		0000352825-25-000032
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250220
FILED AS OF DATE:		20250224
DATE AS OF CHANGE:		20250224

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Rolli Sara Fay
		CENTRAL INDEX KEY:			0002048182
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-10436
		FILM NUMBER:		25658264

	MAIL ADDRESS:	
		STREET 1:		C/O L.B. FOSTER COMPANY
		STREET 2:		415 HOLIDAY DRIVE, SUITE 100
		CITY:			PITTSBURGH
		STATE:			PA
		ZIP:			15220

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FOSTER L B CO
		CENTRAL INDEX KEY:			0000352825
		STANDARD INDUSTRIAL CLASSIFICATION:	WHOLESALE-METALS SERVICE CENTERS & OFFICES [5051]
		ORGANIZATION NAME:           	07 Trade & Services
		IRS NUMBER:				251324733
		STATE OF INCORPORATION:			PA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		415 HOLIDAY DR
		CITY:			PITTSBURGH
		STATE:			PA
		ZIP:			15220
		BUSINESS PHONE:		4129283431

	MAIL ADDRESS:	
		STREET 1:		415 HOLIDAY DR
		CITY:			PITTSBURGH
		STATE:			PA
		ZIP:			15220
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wk-form4_1740435752.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-02-20</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000352825</issuerCik>
        <issuerName>FOSTER L B CO</issuerName>
        <issuerTradingSymbol>FSTR</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002048182</rptOwnerCik>
            <rptOwnerName>Rolli Sara Fay</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O L.B. FOSTER COMPANY</rptOwnerStreet1>
            <rptOwnerStreet2>415 HOLIDAY DRIVE, SUITE 100</rptOwnerStreet2>
            <rptOwnerCity>PITTSBURGH</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>15220</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>SVP, Operational Admin</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-02-20</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>980</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4978</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-02-20</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>382</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5360</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents the number of Performance Restricted Stock Units earned under the 2023-2025 Long Term Incentive Plan granted on 2/14/2023 upon certification of performance results by the Compensation Committee at 48.4% for the annual period ended December 31, 2024.  The earned Performance Restricted Stock Units will settle at the end of the performance period on December 31, 2025, upon certification by the Compensation Committee.</footnote>
        <footnote id="F2">Includes 2,116 Performance Restricted Stock Units earned under the 2023-2025 Long Term Incentive Plan granted on 2/14/2023; those 2,116 Performance Restricted Stock Units will settle at the end of the performance period on December 31, 2025, upon certification by the Compensation Committee.</footnote>
        <footnote id="F3">Represents the number of Performance Restricted Stock Units under the 2024-2026 Long Term Incentive Plan granted on 5/23/2024 upon certification of performance results by the Compensation Committee at 25.8% for the annual period ended December 31, 2024.  The earned performance restricted stock units will settle at the end of the performance period on December 31, 2026, upon certification by the Compensation Committee.</footnote>
        <footnote id="F4">Includes 382 Performance Restricted Stock Units earned under the 2024-2026 Long Term Incentive Plan granted on 5/23/2024; those 382 Performance Restricted Stock Units will settle at the end of the performance period on December 31, 2026, upon certification of the Compensation Committee.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/Sara Fay Rolli by Judith Balog, attorney-in-fact</signatureName>
        <signatureDate>2025-02-24</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
