yes you do if you are taking actual expense deduction (regular method) for home office. you must exclude the cost of the land from the home cost. then the home depreciation is prorated based on square footage of home-office to total square footage of home. Part III of form 8829
Taxpayers using the regular method must determine the actual expenses of their home office. These expenses may include mortgage interest, insurance, utilities, repairs, and depreciation.
Generally, when using the regular method, deductions for a home office are based on the percentage of your home devoted to business use. So, if you use a whole room or part of a room for conducting your business, you need to figure out the percentage of your home devoted to your business activities.
Requirements to Claim the Home Office Deduction
Regular and exclusive use.
Principal place of your business.