Is your roof busy? What I mean by this is, does your roof have a lot of "stuff" on it? Having to roof around skylights, air conditioners, pipes, exhaust fans, etc. will add to the cost of the roof because it requires additional labor and materials.
Factor Two: Is your roof cut-up? Are there a lot of hips and valleys? Roofing a bunch of hips and valleys also can add to the roof cost.
Factor Three: What type of roof deck do you have? The roof deck is the structural element your roof is installed over. For commercial roofing, deck types are steel, concrete, light weight concrete, gypsum, cement fiber, and plywood. Varying deck types create varying roof costs.
Factor Four: How tall is your building? If your building is two stories, there's typically not much change in the roofing price from that of a one-story building. But the higher you go from there, the more the cost goes up because you have to have special equipment and added labor to get the materials up onto the roof.
Factor Five: How accessible is the roof? Some buildings do not have good access and the roofing materials have to be torn off and carried over to a dumpster. It can greatly slow down the roofing process.
Factor Six: Are there parapet walls? Many commercial roofs have parapet walls, which are a raised wall at the perimeter of the roof and can be anywhere from one foot to 15' high. Many of these walls require roofing material to be installed on them, thereby adding labor and material to the job and costing more if the roof edge was just flat.
Factor Seven: What type of new roof is being installed? Just like cars, you have different types of roofs that can accommodate different budgets. For instance, on low slope (flat roofs) roofs you have a 45 mil TPO single-ply which is less than a two-ply modified bitumen roofing system.
IMPORTANT NOTE: There are many other products that go into a new roofing system. Just because one type of roof covering is potentially half the cost of another, it doesn't mean the overall roof price is going to be half. There are a lot of other roof system components that are involved - i.e. insulation.
Factor Eight: How is the new roof going to be installed? On flat roofs there are some installation variables that can have a pretty profound effect on the overall cost. For example, with a single-ply roof, is it going to be adhered or is it a ballasted roof? If it is adhered, is the adhesive water-based or solvent-based? These plus many more variables can greatly affect the roof cost.
Factor Nine: Insulation. One of the most expensive components in commercial roofing is the roof insulation. Most building codes require a minimum thermal resistance value (R-value) of at least R-19. In commercial roofing this equates to about 3" of polyisocyanurate roof insulation ("iso" for short), a very common roof insulation. If ISO runs at about $32 per inch of thickness per 100 square feet of roof area and you install 3" of iso insulation, you would be looking at about $96 per 100 square feet. If your commercial building is 10,000 sq. ft. that would equate to an added cost of $9,600- not including the labor and materials required to fasten/adhere it.
Factor Ten: Who makes the material? Just like with cars, there are different companies manufacturing the same type of product. While prices don't typically vary a lot, there will be differences, just like a Chevy 1/2 ton pickup has a slightly different price that a Ford 1/2 ton pickup.
So how much does a new roof cost? Without knowing at least some of the variables as stated above it is virtually a guess and could be very far off from the actual price, which would only disappoint and frustrate many people. Most roofing contractors will provide free estimates so our advice is to call a local, well-established roofing company and have them visit your property and provide you with a thorough estimate.