Getting rid of house flies usually requires a mix of indoor and outdoor treatment measures. This is especially true if you have pets that defecate in the yard, compost piles, small bodies of water close by, live near a farm or have unclean trash bins or dumpsters nearby. While eliminating all house flies on your property is not realistic, you can control the fly population to a manageable level.
For a small outdoor population you can choose to spray the exterior of your structure with a residual concentrated insecticide. This method should also be used in conjunction with one of the methods below if you have a medium to high population. Dilute the insecticide with water in the hand pump sprayer as directed on the product label.