In my years as a health inspector, I have shut down restaurants, failed apartment buildings and flagged homes for roach infestations that the occupants did not even know they had. The reason is simple. Most people do not know what they are looking for. By the time roaches are visible in the daytime, the infestation is already severe.
Here is what I look for and what you should too.
The Rule of Ten
The most important thing to understand about roach infestations is the rule of ten. For every roach you see, there are approximately ten more you do not. Roaches are nocturnal and spend the vast majority of their time hidden inside walls, appliances and furniture. If you are seeing roaches during the day, the colony is so large it is forcing members out of hiding due to overcrowding. That is a severe infestation.
Signs to Look For
Droppings Roach droppings look like black pepper or coffee grounds. You will find them along baseboards, inside cabinet corners, under appliances and anywhere roaches travel frequently. The more droppings you find, the larger the infestation.
Egg cases Roach egg cases (called oothecae) are small, brown, oval-shaped capsules about the size of a tic-tac. Each one contains 30 to 40 eggs. Finding even one egg case means reproduction is already happening in your home.
Shed skins Roaches shed their exoskeleton as they grow. Finding shed skins in hidden areas is a sign of an established, growing colony.
Smell A large roach infestation has a distinct musty, oily odor. If you notice an unusual smell coming from behind appliances or inside cabinets, take it seriously.
Grease marks Roaches leave dark grease marks along the routes they travel regularly. Look along baseboards, walls and the edges of appliances.
Seeing them during the day This is the most serious sign. Roaches are nocturnal. Seeing them in daylight means the colony is overcrowded and food is scarce. Act immediately.
What to Do
If you find any of these signs, do not wait. Roach infestations do not resolve on their own and they grow exponentially. A small infestation treated immediately is manageable. The same infestation left for two months becomes a serious problem.
The most effective treatment I have seen homeowners use is professional-grade gel bait applied in the hotspot areas. It addresses the colony at the source rather than just the visible individuals.