Larger jobs or those that require more specialized cleaning usually charged anywhere from 5 cents - 55 cents per square foot. Most companies charge separately for labor-intensive special services such as stripping and waxing floors 25 cents - 50 cents a square foot), carpet cleaning ($20 -$40 an hour), and cleaning microwaves or refrigerators ($10 -$35 per appliance). Generally the larger the office, the lower the cost per square foot. Basic nightly janitorial service for a 20,000-square-foot office in a major city can run 5 cents - 10 cents per square foot or $2,000 -$4,000 a month. Similar service for a typical 6-room, 2,000-square-foot office with a bathroom and a kitchenette in a less urban area might cost 10 cents - 55 cents per square foot or around $800 -$2,000 a month.