Capital improvements

If you build an addition to your house, build interior walls, or pave a previously unpaved driveway, you are making capital improvements. These things ultimately increase the value of your house.

You do not take capital improvements into your calculation of repairs and maintenance for your business, because there are income tax implications to doing so in many jurisdictions, that the discussion of which are beyond the scope. Ask your accountant.

Repairs that affect the whole house

Some examples of these types of repairs are duct cleaning, water­softener repair, roof repairs, and lawn cutting. These expenses relate to the business square footage as well as your personal square footage. These repairs and maintenance expenses will be prorated based on square footage, just as your other house expenses are.

Repairs that affect only the personal square footage

Expenses such as repainting your master bedroom or fixing the plumbing in the upstairs bathroom in no way relate to the business use of the house. You would therefore not use any of these types of expenses in your calculations.