Codes vary, I believe the national code is ice shield 24" past the interior side of the exterior wall. In other words if you have an 8" overhang 3' of ice shield is usually enough, but this also depends ont he pitch of the roof. In most cases 3' of ice shield is not enough. If your overhang/soffit is 1', then 3' of ice shield is likely not to code. Contact your local building department and ask. On the majority of our jobs we install 6' at the gutter lines while our competitors who don't understand the code install only 3'. I should also mention some villages around here have amendments to the national code requiring 36" past the exterior wall. In this case more is better, and ice shield is cheap insurance.
Code says nothing about valleys, but valleys are very very prone to ice back up, therefore we install 3' or more of ice shield in the valleys. We will also preflash all problem areas including the chimney with ice shield. This also includes valleys, pipes, skylights etc...
If someone is flashing the chimney but not using aluminum, what are they using? Copper, steel, rubber? Copper or steel or aluminum is fine, stay away from someone using a membrane flashing. As for sealing the masonry, I don't. If it's necessary sure, but 99% of chimneys might need a little spot pointing. Sounds more like marketing to me IMO. Nothing wrong with sealing the masonry, but if it's not necessary then why bother? This is truly something to be approached on a case by case basis.
I offer a 10 year workmanship guarantee on my shingle jobs. However this year I began marking a standard Certainteed 5 star Sure start upgraded warranty into my jobs for 25 years. The point I am trying to make is simple: Who is backing the guarantee, roofer or manufacturer? In either case a warranty won't keep the water out, an intent to do the job right in the first place matters most. Truth be told, any major defect will usually show within the frst few seasons, while minor short cuts, like re-using flashings, usually show up within 5-7 years. I am sure you have noticed that the average roofer warranty/guarantee is 5 years, at least in my area it is.
Some other things you should be concerned with is not only chimney flashings but ALL flashings. All flashings should be replaced in part of the shingle roof project. What about ventilation? All ventilation should be replaced and in most cases, I find ventilation needs to be improved. Improved ventilation may mean changing the vent type, or increasing the ammount of vents. Bathroom and kitchen vents also need to be added on most houses older than 40 years.
Some links you should read before you sign any contracts:
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