Important Additional Information Regarding Proxy Solicitation

Griffon filed its proxy statement and associated WHITE proxy card with the U.S. Securities and Exchange Commission (the “SEC”) on December 30,2021 in connection with the solicitation of proxies for Griffon’s 2022 Annual Meeting (the “Proxy Statement”). Shareholders as of the record date of December 28, 2021, are eligible to vote at the 2022 Annual Meeting. Griffon, its directors and certain of its executive officers will be participants in the solicitation of proxies from shareholders in respect of the 2022 Annual Meeting. Details concerning the nominees of Griffon’s Board of Directors for election at the 2022 Annual Meeting and information regarding the names of Griffon’s directors and executive officers and their respective interests in Griffon by security holdings or otherwise is set forth in Griffon’s Proxy Statement. BEFORE MAKING ANY VOTING DECISION,INVESTORS AND SHAREHOLDERS OF THE COMPANY ARE URGED TO READ ALL RELEVANT DOCUMENTS FILEDWITH THE SEC, INCLUDING THE PROXY STATEMENT AND ACCOMPANYING WHITE PROXY CARD, AND ANY SUPPLEMENTS THERETO, BECAUSETHEYCONTAIN IMPORTANT INFORMATION. Investors and shareholders may obtain a copy of the Proxy Statement and other relevant documents filed by Griffon with the SEC free of charge from the SEC’s website, www.sec.gov, or by directing a request by mail to Griffon Corporation, Attention: Corporate Secretary, at 712 Fifth Avenue, New York, NY 10019, or by visiting the investor relations section of Griffon’s website, www.griffon.com.

Forward-looking Statements

“Safe Harbor” Statements under the Private Securities Litigation Reform Act of 1995: All statements related to, among other things, income (loss),earnings, cashflows, revenue, changes in operations, operating improvements, the effects of the Hunter Fan transaction, industries in which Griffon operates and the United States and global economies that are not historical are hereby identified as “forward-looking statements” and may be indicated by words or phrases such as “anticipates,” “supports,” “plans,” “projects,” “expects,” “believes,” “should,” “would,” “could,” “hope,” “forecast,” “management is of the opinion,” “may,” “will,” “estimates,” “intends,” “explores,” “opportunities,” the negative of these expressions, use of the future tense and similar words or phrases. Such forward-looking statements are subject to inherent risks and uncertainties that could cause actual results to differ materially from those expressed in any forward-looking statements. These risks and uncertainties include, among others: current economic conditions and uncertainties in the housing, credit and capital markets; Griffon’s ability to achieve expected savings from cost control, restructuring, integration and disposal initiatives; the ability to identify and successfully consummate, and integrate, value-adding acquisition opportunities; failure to consummate or a delay in consummating the Hunter Fun transaction; increasing competition and pricing pressures in the markets served by Griffon’s operating companies; the ability of Griffon’s operating companies to expand into new geographic and product markets, and to anticipate and meet customer demands for new products and product enhancements and innovations; reduced military spending by the government on projects for which Griffon’s Telephonics Corporation supplies products, including as a result of defense budget cuts or other government actions; the ability of the federal government to fund and conduct its operations; increases in the cost or lack of availability of raw materials such as resin, wood and steel, components or purchased finished goods, including any potential impact on costs or availability resulting from tariffs; changes in customer demand or loss of a material customer at one of Griffon’s operating companies; the potential impact of seasonal variations and uncertain weather patterns on certain of Griffon’s businesses; political events that could impact the worldwide economy; a downgrade in Griffon’s credit ratings; changes in international economic conditions including interest rate and currency exchange fluctuations; the reliance by certain of Griffon’s businesses on particular third party suppliers and manufacturers to meet customer demands; the relative mix of products and services offered by Griffon’s businesses, which impacts margins and operating efficiencies; short-term capacity constraints or prolonged excess capacity; unforeseen developments in contingencies, such as litigation, regulatory and environmental matters; unfavorable results of government agency contract audits of Telephonics Corporation; our strategy, future operations, prospects and the plans of our businesses, including the exploration of strategic alternatives for Telephonics Corporation; Griffon’s ability to adequately protect and maintain the validity of patent and other intellectual property rights; the cyclical nature of the businesses of certain of Griffon’s operating companies; and possible terrorist threats and actions and their impact on the global economy; the impact of COVID-19 on the U.S. and the global economy, including business disruptions, reductions in employment and an

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