For Sheds, you can calculate the surcharge off of the base price only or the subtotal. You can also designate whether the surcharge is taxable.

In the Amounts section, you can add a surcharge percentage and/or add a flat fee amount. You can also round it to 0 or to other custom $ amounts.

In the Vary surcharges by section you can add certain conditions. In the image below, the surcharge will be 10% of the base price for all buildings except if a building has metal siding. If siding is metal, the surcharge will be 20%.