Sec Form 4 Filing - Paxton Robert @ MASONITE INTERNATIONAL CORP - 2021-02-25

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Paxton Robert 2. Issuer Name and Ticker or Trading Symbol MASONITE INTERNATIONAL CORP [ DOOR] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) See Remarks (Last) (First) (Middle) C/O MASONITE INTERNATIONAL CORPORATION, 1242 EAST 5TH AVENUE 3. Date of Earliest Transaction (MM/DD/YY) 02/25/2021 (Street) TAMPA, FL33605 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Shares 02/25/2021 F 890 ( 1 ) D $ 110.75 13,903 D Common Shares 02/25/2021 F 181 ( 1 ) D $ 110.75 13,722 D Common Shares 02/25/2021 F 200 ( 1 ) D $ 110.75 13,522 D Common Shares 02/27/2021 F 341 ( 1 ) D $ 109.72 13,181 D Common Shares 02/27/2021( 2 ) A 3,642 ( 3 ) A $ 0 16,823 D Common Shares 02/27/2021 F 1,434 ( 4 ) D $ 109.72 15,389 D

3. Transaction Date (MM/DD/YY) Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Paxton Robert C/O MASONITE INTERNATIONAL CORPORATION 1242 EAST 5TH AVENUE TAMPA, FL33605 See Remarks Signatures /s/ Robert E. Lewis, as attorney-in-fact 03/01/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Shares withheld by the Issuer to cover tax withholding obligations arising from the delivery of shares in connection with the settlement of vested Restricted Stock Units. ( 2 )The date of the transaction represents the date on which the financial performance criteria of a previously granted performance-based restricted stock units were determined to have been satisfied. ( 3 )The performance-based restricted stock units were previously granted on February 27, 2018 and were subject to the achievement of certain pre-established financial metrics based on the results for fiscal year 2020. On February 22, 2021, the Compensation Committee of the Issuer's Board of Directors certified the performance metrics and determined the number of performance-based restricted stock units that were earned. ( 4 )Shares withheld by the Issuer to cover tax withholding obligations arising from the delivery of shares in connection with the settlement of vested Performance Restricted Stock Units

Remarks: Senior Vice President, Human Resources

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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