To　facilitate　the　regular　monitoring　of　exterior　building　walls　for　ensuring　the　personal　safety　of　residents　living　near　the　building,　we　propose　a　method　for　automatically　detecting　small　defects　via　images　of　the　building　wall　surface　captured　using　high-resolution　cameras.　With　this　method,　the　risks　caused　by　loosening　or　cracking　tiles　can　be　easily　identified.　First,　the　original　detection　task　is　divided　between　a　large-scale　segmentation　task　of　non-tile　regions　and　the　small-scale　detection　of　defects.　Second,　corresponding　low-resolution　deep　models　are　trained　and　applied　to　these　tasks.　Lastly,　the　results　obtained　from　these　multiscale　tasks　are　fused　to　obtain　the　comprehensive　detection　of　small　defects.　Our　experimental　results　indicate　that　the　accuracy　and　efficiency　of　the　proposed　algorithm　are　superior　to　those　of　the　single-scale　method.　The　proposed　method　has　achieved　excellent　results　in　real-world　applications　in　a　residential　area,　which　confirms　its　high　practical　value.　Copyright　©2021　Journal　of　Harbin　Engineering　University.