<p>How long a roof last depends on where you live, how well the roof was done in the first place and what kind of roofing material was used, there is no set number. I have a split and due to construction about 15 years ago, the two rooves are different ages. The low side is now around 26 years old but has been holding up, the asphault tiles are not popped up, plus it is a second layer. I have kept an eye on it, checked the attic under the roof, and have seen no signs of leaks or issues, but it is going to need to be replaced in the next year or so. In most places, rooves expire anywhere between 20 and 30 years. </p>
<p>You only need to do a tear off if there are already two layers of shingles there, and the roofers in my area (it depends where you live) don’t recommend doing a tear off if you don’t have to (and if you think about it, they make more money doing a tear off…). </p>
<p>I agree with others, best choice is to find an experienced inspector, they don’t have a financial interest in selling you a new roof.</p>
<p>My other piece of advice is general, try to find a firm that is local and has done roofs in your area, and don’t take the lowest bid without knowing the firm! There are a ton of guys in my area who cruise around my area and leave cards and flyers that advertise cheap prices, but take it from me, don’t use them, most of those guys pick up laborers working as day laborers and they use questionable materials.Knowing where the guy is located, and that his reputation is on the line, tends to make them work better, and if a bit more expensive, is worth it. </p>
<p>Couple of things to look for, whether code or not:</p>
<p>-In my area it is code to have an underlayment put on the roof (I think it is called ice block), it is basically a rubberized membrane that is put under the shingles from the edge of the gutter and up about 3 feet, in the case you get a winter ice dam and ice creeps up on the roof. Works great, have survived several cases of these and no damage/drips.</p>
<p>-You also might look into roofing that has a vent at the peak of the house, helps ventilate the attic area.</p>