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.
Asphalt Roof Costs. Asphalt roof costs range from $2.50 to $6 per square foot fully installed. Asphalt shingled roofs are either a composite organic shingle or the lighter woven fiberglass option.This is one of the least are expensive roofing options, significantly less than concrete and clay tiles for instance.sphalt Roof Costs. Asphalt roof costs range from $2.50 to $6 per square foot fully installed. Asphalt shingled roofs are either a composite organic shingle or the lighter woven fiberglass option.