Timber framing can be tarred on exposed exterior faces when a traditional dark protective finish is wanted, but the wood must be dry, sound, and able to breathe and drain properly.
Tar has a natural place on rustic and heritage timber framing because it protects, darkens, and visually unifies large pieces of wood. It is most relevant to exterior frames, outbuildings, garden structures, porches, sheds, and timber that will be maintained as a visible surface.
Prepare the frame by removing loose dirt, algae, dust, and failing old coatings. Brush tar into checks, joints, peg holes, end grain, and weather-facing surfaces. Do not flood deep joints where moisture is already trapped. The coating should help shed rain, not seal damp wood into a hidden pocket.
A tarred frame will weather unevenly because beams, posts, braces, and sheltered undersides receive different amounts of sun and rain. That is normal. Maintenance should focus on exposed tops, lower areas, and cracks where bare wood appears rather than coating every surface heavily every time.