Boolean operators are specific words used to combine keywords to improve the chances of finding relevant information. The most commonly used Boolean operators are AND, OR and NOT. Search results will contain both of the terms humour and therapy. Using AND decreases the number of results, because each time a keyword is added, the focus of the search is narrowed. Search results will contain one, or both, of the terms humour or laughter or comedy. Using OR increases the number of results, because a broader range of keywords is searched.
The actual cost of a flat roof depends on your location, the materials used, the complexity of the installation, and other factors. 1  Building a flat roof costs approximately $1.50 to $10.00 per square foot. 2  Assuming an average roof size of 1,500 square feet, that s a total cost of $2,250 to $15,000.
Note: many professional roofing contractors price their roofs on a per square basis, where one square is a 10 by 10 foot area or 100 square feet. Thus, your total cost in square terms could range from $350 to $1,200 per square of metal roofing installed. For comparison, most asphalt shingle roofs will cost anywhere from $300 to $700 per square installed depending on the material choice, roof complexity, installerâs credentials, your geographic area, time of the year, and so forth.