Timber decay and infestation in buildings. Biocides have been used for many years and are called “preservatives”; this term suggests negligence if timbers are not treated. But this is expensive and has little effect, it also reintroduces water into the building. We follow Historic England recommendations; an appropriate conservation approach is required. The primary control strategy for timber decay and infestation must be based on repairs to remove the source of dampness that is causing the defects. The moisture content of the timbers should be kept below the level at which timber defects will occur. In the above case there is evidence of past timber decay and death watch beetle, but the core of the post is still solid and strong enough to continue is structural function in a restored barn conversion.