Answer: Yes. The IRS Child Care Audit Techniques Guide clearly states that your basement and garage must be included as part of the total square feet of your home. Many child care providers use these areas on a regular basis for their business and can therefore count the space in their Space percent calculation.
For example, you might have in your basement: laundry room used for your business; furnace and hot water heater used for your business, storage of household items used for your business (tools, lawn mower, garden items, etc.), etc. This would make your basement regular use for your business.
In your garage you might have: car used for business, garden tools, garbage can, bicycles, and other household items used for your business. This would make your garage regular use for your business.