One thing which is not often considered when hiring a roofing contractor is what supplier the contractor uses for the roofing material, this could be slate, metal, concrete/clay tile, shingles etc.
Most contractors will have suppliers they regularly use and in hiring that contractor you are essentially also using their chosen suppliers. This has good and bad implications, on the good side the contractor will have probably decided on this supplier because their products give them the quality and price that they consider best reflects their ethos and you will have no doubt decided on this contractor because you have also done your homework and decided on what you want from the contractor. But on the bad side you could also be committing to a product that although your contractor considers being right it may also bring with it many issues you should also consider.
Here are some questions you should consider asking or looking into:-
1. Is this a new product and the contractor has been offered a good rate to use it and your home is now effectively an active trial and with any new product it could quite easily fail and the supplier with it.
2. Is there a possibility there may be further additions in future years and then a need for more of this product? This may not be a bad thing but does your contractor hold exclusive rights to supply of this product and leaving you really with only them as an option because sometimes you may wish to change to a different contractor for various reasons (this is a whole other area of discussion which I will deal with at a later date).
3. Could there be future supply issues? Even consider over-ordering the quantities required as although many contractors will leave extra material behind if future repairs are required some will not so you then have to contact them and again you may not wish to! Obviously this is not really relevant to metal sheets as they will rust if not stored correctly.
4. To further expand on the previous point if the products imported then you should really consider ordering extra as supply does become an issue if you have to import from another country.
In summary when you choose your roofing contractor you will decide what you want from them be it quality, price or speed. Hopefully you can get all three but whoever you hire remember to do your homework on the product they will use and its supply.