Some commercial housing offers textured metal subfloors, or slide-out wooden nest trays. It's also important that subfloor material drain well, and not retain moisture. Materials such as outdoor carpeting are not suitable. Access to individual compartments during the nesting season allows for easy removal of House Sparrow and European Starling nests. Compartment access also facilitates regular monitoring, and cleaning at season's end.
Some designs now feature removable nest trays that allow for easier monitoring and cleaning.
Any type and size of pole, wood or metal, is easily climbed by several predators of Purple Martins, including raccoons, rat snakes, and squirrels. Wood posts or poles can also be climbed by domestic cats and bobcats. Aerial predators, such as hawks, crows, and owls, will also raid martin housing. Crows and hawks will often take nestlings that are waiting at entrance holes. The solutions are either an external barrier guard, like a bird cage, fastened against porches, or, deeper compartments, with offset entrances, and internal baffles.