the difference between a political and a physical boundary is that a physical map shows geographical features like mountains and rivers while a political map shows boundaries.
Standard Weight. Standard asphalt shingles generally weigh about 190 pounds per 100 square feet, based on information from U.S. Inspect, a property inspection company. The weight of asphalt is especially important if you want to install a new layer of asphalt roofing over an existing layer.A roof measuring 1,600 square feet that has two layers of standard asphalt shingles on it is holding about 6,000 pounds of shingles..S. Inspect indicates that dimensional shingles can be 50 percent heavier than standard asphalt roofing. Therefore, they could weigh about 285 pounds per 100 square feet. Heavier shingles reduce the chance the underlayment will wrinkle, according to the National Roofing Contractors Association.
A square of shingles weighs 250 lbs. to 400 lbs. depending upon the type of shingle (see below). An important thing to keep in mind is that many roofs have multiple layers of shingles, so you must factor that in when determining weight and choosing a dumpster. For example, a 20 square roof with two layers of shingles will actually produce shingle waste equal to 40 squares. Know how many layers of existing shingles are on your roof prior to ordering the dumpster to ensure you choose the right one and avoid having to get a second dumpster later.