Ok to allow tenant to store a grill on the back porch/patio?

[Daniel Alfandre]

One of the house rules and regulations ezlandlordforms.com gives me the option to choose to put in the lease is: 

"Charcoal and Gas Barbecue grills may not be used or stored on any patios, porches, and/or landings."

My unit is a rowhouse and I don't see a problem with a tenant storing a grill in any of these areas behind the house (not in front).  

Is there a problem with this I'm not seeing?