As long as you are not renting the space to the S-corp, you can take home office expenses.
Please see this publication for details.
Essentially you will be able to deduct a portion of utilities, taxes, insurance, and depreciate a percentage use of the office as part of the FMV of the home.
this is subject to a 2% floor for schedule A and income limitations.
NOTE: as s-corp owners you are required to pay yourselves a W-2 wage reasonable for the amount of business revenues and level of work as corporate officers,
You do not do a cost. YOu are not renting it out to the S-corp.
What you do is start with the percentage of floor space your office is of the entire house.
Say for example your office is 10 X 12. that equals 120 square feet.
If your house is 2400 square feet, then you create a percentage of that. your office is 120/2400 ths of the total house. (happens to be 5%).
So you can take 5% of:
1. utility charges
In a nut shell. If your home's FMV today (day you put the space to use as an office) is 500,000 you can depreciate 5% of that 500,000 to arrive at a depreciation expense. Use MACRS convention for 15 year property. The depreciable basis in my example is 25,000.
The publication to which I gave you the link provides several descriptions of other expenses you can take for your home office.
That publication also describes in detail how to do figure the percentages.