i've been installing asphalt shingle roofs, rubber roofs, red cedar roofs since 1973.
We often get to go back and inspect roofs and get a good feel for longevity and why some roofs fail and others outllast the mfr's projected life.

1st in asphalt roofs: mostly it is the mfr. Some asphalt shingles are superior to others and it varies from mfr'g plant to plant, within the same Brand.
Sometimes you get a twenty year roof that still looks and performs great after 30 years. and it has less to do with exposure than how the shingle was made.
If they get the formulation right and the right matt, and the shingle thickness, and the aggressive glue that makes one shingle stick to the one below it,
AND it is correctly installed, then you will get a long lasting roof.

Now the big boys in the roofing industry are touting "Lifetime Warranty", well, I guess we'll find out what that means in about 30 years.

Some roofs curl , lose all of their granules, split from top to bottom all with in 3 years or so.... these are 25 year .. 30 year shingles... this is a mfr'g defect.
That is the primary cause of roof failure in my opinion.
the 2d factor is orientation.... if you have a ridge that runs East-West, the south roof will wear out about 10 years earlier than the north roof ( assuming a 30 year shingle )

So ... asphalt shingles ---- short life---- mfr'g followed by orientation

Red cedar shingles ( roof )... using them on a slope too low to get good drainage... a low slope roof soaks in more water than a high pitched roof.. this wetting cycle will shorten the life of the RC roof.. and if the roof stays wet long enough, it will actually rot and will be a perfect host for mildew, lichen, fungus and rot.

if you want a long lasting RC roof you should have higher pitches and it should be installed on either ShingleBreather, or furring, or on gapped sheathing , so the shingles can dry form below and reduce their wetted period . If they can dry fast enough, then they will not rot.
The other factor is erosion... rain will wear off wood fibers and the shingle will keep geting thinner and thinner until the course below shows thru.
One way to combat this is to use a "Thick Butt" shingle ( do not confuse "shakes" and "shingles" ), which is 5/8" thick at the butt instead of the normal 3/8"

Rubber roofs.. thickness & installation are the biggest factors

Steel roofs... I have yet to find a mfr' who will warrant their roof for Coastal installations... none of them aree designed to stand up to salt air.. especially fwith field cuts and raw edges.

YMMV

Kermit,

A lecture that I attended at a home show on the coast of Florida advocated aluminum roofs instead of steel for long lasting roofs in coastal areas.  Do you think aluminum will outlast steel in coastal areas?

don't know...  did they have any Mfr's websites to visit ?  like to know what gauge they are using.. is it standing seam ?

i'd worry about denting and galvanic reaction, but i bet the mfr's address that

How about stainless steel shingles? If its thin enough it might be affordable.

Posted By albertbrent on 07 Feb 2011 04:24 AM
The primary function of a roof is to provide protection from all the elements in any climate. There are lot of factors that can affect your roof but here are some major factors that affect your roof life. The sun is the most damaging factor to your roof because it delivers a combination of ultraviolet rays and heat that can prematurely age a roof. The roof is also not spared during the winter months, snow and ice can damage your roof. The melting and refreezing of ice and snow on your roof can push your roofing material up which can lead to leaks in your roof. Rain, moisture, wind algae and moss growth are some other factors that damage your roof. If your roofs are not protected from these factors it will definitely cause damage that only experts could fix. Damages caused by these factors can easily be prevented with enough maintenance.

Yes! a lot of people do not realize that moss stores a lot of water and over time this water freezes and expands causing damage to roof tiles and the structural integrity of the roof! I just recently bought a tool to clean my roof from Roof Scraper LTD here in the UK it is common to get your roof & gutters cleaned regularly to prevent any issues and to keep up with maintenance.

Several factors affect your roof lifespan. Sun exposure with UV rays and heat harsh winter weather causing ice dams rain and moisture, strong winds algae and moss growth, and regular maintenance play crucial roles. Investing in quality materials also extends my/your roof life...