Removing damp areas from the interior and exterior of a home, sealing off entry points into a house and using chemical pesticides are recommended ways to control millipede infestations. Millipedes thrive in outdoor and indoor environments with a constant supply of moisture.
Check for leaky pipes, large mulch or leaf piles, and flowerbeds that retain moisture for a long period of time, as these are all areas where millipedes congregate and multiply. Water flowers and lawns in the morning on a sunny day so the water is dry by the afternoon. An excess of mulch in flowerbeds or around the base of a structure also attracts millipedes, as mulch is an excellent retainer of moisture.
If you eliminate excess moisture outside a structure but can't eliminate the moisture inside it, block entry points to the structure to keep millipedes out. Seal cracks around doors and windows, and check for small holes in walls or vents located close to the ground. If you can't eliminate moisture or close entry points to the structure, spray pesticides around the base of the structure to form a chemical barrier. This barrier prevents millipedes and other insects from crossing into the structure, though it doesn't necessarily eliminate millipede infestations outside the structure unless you apply the chemicals in a wide area.