Hands down, the most common question we hear is, "How much will a metal roof cost?" And while we'd love to just hand over a price sheet, it's a bit more complicated than that. Variables affecting price include things like the size, complexity and location of a given project, desired replacement material and profile, installer preferences, and - a biggie - preexisting conditions.
While it's easy to come up with ballpark numbers of a material package for a project based on the size and complexity of the roof in the style and material that a homeowner thinks is nice, it can get tricky when you consider the existing roof. Why? Because there's simply no way of guessing how much preparation will be required - and at what cost. It boils down to this - if the existing layer(s) of a roof need to be removed and they reveal rotten or or non-existent decking, then the price of bringing that up to code might be equal to all of the other labor required to complete the job.
Put another way: Figure the the price of one metal roof project may be $3 a square foot for material and $3 a square foot for the installation labor on a new project, while an identically sized job with the same configuration and metal roofing material might incur a labor cost anywhere for $3 (if the new metal can be installed directly over the existing roof with little or no preparation) to more than $10 if a lot of demolition and construction is required to ready the structure for its new roof. That's quite a difference! This is more than likely the case regardless of the new roofing material chosen, by the way. If a great amount of preparation is required, the price tag is going to incease regardless of whether you intend to use metal, asphalt, concrete or synthetic roofing material.
So what's the take away here? When your existing roof has more than one layer of material, you should assume that you will incur some significant preparation expense when you re-roof. And if you walk on the existing roof and it seems "soft" underfoot, then it's likely you'll need to consider spending more than just the price of removing the old roofing and installing the new.