X0609 4 2026-04-16 0 0001585389 SmartStop Self Storage REIT, Inc. SMA 0001672825 Mueller David J false 10 TERRACE ROAD LADERA RANCH CA 92694 1 0 0 0 0 Common Stock 2026-04-16 4 S 0 425 31.78 D 6340 D Long-Term Incentive Plan Units 0 Common Stock 7234.25 7234.25 D Long-Term Incentive Plan Units 0 Common Stock 9598 9598 D The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on December 15, 2025. Includes shares of Common Stock previously reported as being owned by the Reporting Person, less 0.87 shares of Common Stock that were redeemed by the Issuer in connection with a fractional share redemption conducted by the Issuer with respect to its outstanding Common Stock as of July 30, 2025. Represents long-term incentive plan units ("LTIP Units") of SmartStop OP, L.P., the Issuer's operating partnership (the "Operating Partnership"). Vested LTIP Units are convertible into common units of the Operating Partnership ("Common Units"). Common Units are redeemable by the holder for, at the election of the Issuer, shares of the Issuer's Common Stock on a one-for-one basis or the cash value of such shares. Represents 7,234.25 LTIP Units previously reported as being owned by the Reporting Person. The LTIP Units were issued to the Reporting Person in connection with his reelection to the board of directors and vest one year from each such reelection. Represents 9,598 LTIP Units previously reported as being owned by the Reporting Person, which LTIP Units vest ratably over four years commencing on the first anniversary of the issuance thereof, subject to the Reporting Person's continued employment or service through each vesting date. /s/ David J. Mueller 2026-04-17