TurboTax will allow you to enter information for using the first home office for the first 5 months of the year with the 1200 sf compared to the total homesize (excludind new shop).
Bear in mind to qualify these spaces needed to be in use solely and exclusively for your business during those 5 months. Then you will need to add a second home office for the new stand alone shop.
You may have a difference in expenses that are directly attributable to the new shop ( if it is metered separate for example for water and electric ) or you have a different total sq footage when you add the new shop to the old total sq footage to come up with a percentage of use for common usage items.
I think you will see it does really matter.
