Some closing costs of refinancing can be added to your basis I believe, but not all your closing costs. See publication 523 on page 8.
https://www.irs.gov/forms-pubs/about-publication-523
Also note, improvements must be part of the property to count as a basis adjustment. For example, if you replaced the roof in 2005 and again in 2020, only the cost of the 2020 roof is includable in the basis.
