Bogie is correct! Most deed restrictions do not permit structures that are NOT attached to the house. More likely that your storage idea would need to be constructed as physically attached...AND...require the approval of the Architectural Review Committee.
If the deed restrictions for your District are not handy, you can look them up here - as well as review the External Deed Restriction Standards, too:
VCDD Community Standards
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Not sure if I have free time...or if I just forgot everything I was supposed to do!