X0306 4 2021-04-15 0 0001650729 SiteOne Landscape Supply, Inc. SITE 0001776771 Weller Greg MANSELL OVERLOOK 300 COLONIAL CENTER PARKWAY, SUITE 600 ROSWELL GA 30076 0 1 0 0 EVP of Operations Common Stock 2021-04-15 4 M 0 1200 8.02 A 11503 D Common Stock 2021-04-15 4 S 0 1200 178.20 D 10303 D Common Stock 2021-04-15 4 M 0 500 38.73 A 10803 D Common Stock 2021-04-15 4 S 0 500 178.20 D 10303 D Common Stock 2021-04-15 4 M 0 1000 77.04 A 11303 D Common Stock 2021-04-15 4 S 0 1000 178.20 D 10303 D Common Stock 2021-04-15 4 M 0 500 51.59 A 10803 D Common Stock 2021-04-15 4 S 0 500 178.20 D 10303 D Stock Options (right to buy) 8.02 2021-04-15 4 M 0 1200 0.00 D 2025-04-15 Common Stock 1200 6094 D Stock Options (right to buy) 38.73 2021-04-15 4 M 0 500 0.00 D 2027-02-17 Common Stock 500 2500 D Stock Options (right to buy) 77.04 2021-04-15 4 M 0 1000 0.00 D 2028-02-14 Common Stock 1000 6750 D Stock Options (right to buy) 51.59 2021-04-15 4 M 0 500 0.00 D 2029-02-06 Common Stock 500 8222 D The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 sales plan adopted by the Reporting Person on March 5, 2021. 46,472 options were granted on April 15, 2015, and vest and become exercisable ratably in five installments on each anniversary of April 15, 2015, subject to the Reporting Person's continued employment. Prior to the transactions reported on this Form 4, 7,294 of these options that remain outstanding had vested. 8,365 options were granted on February 17, 2017, and vest and become exercisable ratably in four installments on each anniversary of February 17, 2017, subject to the Reporting Person's continued employment. Prior to the transactions reported on this Form 4, 3,000 of these options that remain outstanding had vested. 8,750 options were granted on February 14, 2018, and vest and become exercisable ratably in four installments on each anniversary of February 14, 2018, subject to the Reporting Person's continued employment. Prior to the transactions reported on this Form 4, 5,562 of these options that remain outstanding had vested. 8,722 options were granted on February 6, 2019, and vest and become exercisable ratably in four installments on each anniversary of February 6, 2019, subject to the Reporting Person's continued employment. Prior to the transactions reported on this Form 4, 4,361 of these options that remain outstanding had vested. /s/ Briley Brisendine, Attorney-in-fact for Greg Weller 2021-04-16