Improvements that are part of the kitchen (walls, flooring, etc) are part of your "further investment in this building" and not Expense to be deducted. Think of it like this: the money is right there, every time you use that new sink or walk on that flooring. That is Expenditure (you paid for something) and not Expense (it isn't all gone already or used up already). Expense is Printer paper and Electricity. What you have is invested into the Basis, or total cost for the building you improved. If you only stated you repaired, for instance, that can sometimes qualify as expense. I teach this as the difference between replacing a broken window (repair expense), and putting in all new and better windows (improvement to the building).

Unless you have a kosher or otherwise split kitchen (multiple sinks, etc), it's pretty hard to state 1/3 is only for business and nothing personal happens there.

I recommend you google and read the results:

home office deduction 2019

You can not claim any of the kitchen remodeling costs as a deductible business expense due to the fact that the kitchen is your homes kitchen and not a separate kitchen used exclusively for business purposes.

The cost of the kitchen remodeling is a capital improvement to your home and will be added to the cost basis of your home.  This adjusted cost basis will be used to calculate any capital gain or loss at the time you sell your home so it is important that you keep a record of the remodeling expenses.

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