In round numbers, 22 squares divided by 3 or 4, depending on the shingle, is the number of bundles you should need, not counting the ridges, unless he included that. A regular roofer will include allowances for the ridge shingles. It is true that most established roofers can get better pricing, however, if you can find ones you like on sale, you could probably save some money. When putting on a new roof, it is customary to also install new eave tin.
Contractor can get them at a cheaper price than you can because he does many roofs. Not just one house, so it is bulk buying. He is a preferred client so he get the discount. He may pass that savings on to you.
. The store does not know you from "MUD" so you pay full retail price.
. Some contractors will not do just the labor. You had better find that out first.
If you do find a contractor to work with materials you furnished there probably won't be any guarantee on the job. That's like taking your own eggs into a restaurant for them to cook your breakfast. They can't guarantee you will like it not knowing where the eggs came from.
plain asphalt are usually 3 bundles per sq or 100sq foot of roof area
check the type of shingles your using many have 4 bundle sq
