I have been told it is possible to apply a metal roof on top of the existing asbestos shingles. That seems questionable to me.
I was told that this would act as insulation. Again, that seems questionable. What insulation would you recommend? There is also some damage to several areas of the roof which will require repair before the roof can be replaced. And presently there are no gutters or downspouts.Obviously, I am not knowledgable about many of these issues. Thank you for your help.
Since you are aware of some areas where your roof needs repair i would recommend removing the existing roofing entirely so you can see the true extent of the damage.
Once the sheathing has been repaired i would recommend installing an ice and water shield.
If you are planning on insulating the roof rafters i would recommend spray foam insulation as it will reach all spaces and address any irregular spacing that may exist.
- Please note that not allowing a roof to vent may affect the warranty of the roofing.
- In order to avoid this you could install a cold roof, this is basically a second layer of sheathing, installed over sleepers, to which the roofing would be installed.
Leaders and gutters are important so they should be installed.
Metal roofing is a great option. It's durable and, if standing seam, allows for future installation of solar with minimal penetrations into the roof.
For more information:
Read "Are metal roofs more energy efficient for southern climates than shingles?" a Q&A answered by Anthony Addesso.