Half-timbered buildings constitute a significant part of historic architecture in Europe. Many of them currently require renovation and restoration works aimed at improving their technical condition and comfort of use while maintaining or restoring their original aesthetic values. The article presents the state of preservation of a historic, half-timbered church after over a hundred years of use and the results of its thorough renovation carried out from 2019–2021. The renovation and repair works included, among others, strengthening the foundation walls, installing vertical and horizontal damp-proofing of these walls, replacing biologically corroded, wooden ground beams and other structural elements of the walls and roof, as well as thermal modernization of the walls using aerogel mats and thermal plaster. The basis for developing the scope of renovation and restoration works were analyses and results of diagnostic tests conducted, among others, using non-destructive dielectric, resistive and thermal imaging methods, which revealed excessive moisture in the masonry and biological corrosion of the wooden elements of the foundation walls and the above-ground walls in the ground zone, as well as low thermal insulation of the walls.