Tenant wants to replace deck

[Caleb VanTimmeren]

Hi BP,

I own a duplex and had a tenant reach out about taking down a handicap ramp in the backyard and adding stairs for more yard room.  The handicap ramp is not needed by either tenant currently.  The tenant has lived in the unit for 2 month and has been good thus far.  Should I allow them do do this work themselves and pay the materials themselves?  I wouldn't mind the ramp being removed as it is in rough shape but unsure if I should allow the tenant do it.  My lease states all improvements must be approved in writing by landlord. Any legal issues?

Any responses and help is much appreciated. 

Thanks in advance,