The example you gave is not a tax deductible donation, either business or personal. You can never deduct the value of your time. The term "in-kind donation" might be a little vague and misleading. What the IRS says you can deduct is donations of "property," which then becomes a possession of the organization.
In your example, the only thing you can deduct is direct expenses that you incur in performing services for the church, such as the cost of paper or other materials that you use in designing the building.
