Since the Japanese Building Standards Act was revised in 2000, the installation of steel timber connectors (STCs) to reinforce timber frame (TF) connections has been mandated for new-build TF houses in Japan. However, for the TF houses built before then, more than 40% do not have sufficient STCs and are considered earthquake-prone. This study proposed a simple and easy seismic retrofit technique for such earthquake-prone existing houses. The proposed technique can reinforce TF connections using only plywood and common nails and achieve equivalent performance to the benchmark STCs used in Japanese TF houses, such as the “CP-T type” or the combination of “VP type” and “BP type” STCs. Experiments were performed to compare the proposed technique with the STCs using pullout and full-scale in-plane cyclic tests. The experimental results showed that the proposed technique had a higher seismic performance than the STCs, which was particularly excellent in displacement ductility to prevent a collapse of the TF house without damaging the timbers. The proposed technique will be accepted by many carpenters when retrofitting earthquake-prone existing houses because simple and easy.

We have clarified that external insulation reduces the probability of reinforcement corrosion in reinforced concrete buildings in cold snowy districts by 45–78%. Renovation of external insulation is one of the effective methods for improving the insulation performance and durability of reinforced concrete buildings, but there are almost no data that demonstrate durability. Therefore, the carbonation depth and the cover depth were investigated for six medium-rise-wall type reinforced concrete buildings in Hokkaido, Japan, which had been refurbished for external insulation. As a result, it was clarified that the external insulation suppressed the carbonation depth by 30% or more, even when the bonding method of the external insulation was different. In addition, it was clarified that the external insulation further suppressed carbonation in walls where the carbonation depth tended to increase in snowy cold districts. Specifically, external insulation reduced carbonation by up to 35% on surfaces that tend to dry out due to sunlight, and by 49% on surfaces that are affected by water that deteriorates the concrete surface layer.