I have an old metal roof on an outside porch extension and a tree
hit it and caused several leaks. No holes, just a ripple effect.
I got some bids for power washing and sealing with a rubberized
coating and it was about $1000. The roof cannot be seen by neighbors
so cosmetics were not an issue and I fixed it the following way for
1. elastomeric paint; 25$
2. extension pole; shop around some of these are only 15$
3. brush for pole
4. mini roller with round 'end' for getting into the corners. I could
not find a 'wheel' roller with threads on the end.
Brush off the debris, use leaf blower to blow off grit, etc.
Hose it down and let dry.
Wait for 3 days of sun, then glob on the elastomeric paint into the
seams [there were about 15, each about 15' long, that had to be
treated]. It does not have to be spotlessly clean to stop the leak.
I also put the elastomeric goop on any screw heads I found.
I also figured out how to fix a small rotted section of wood below
one of the leaks with that 'wood hardener' solution by miniwax.
You get a basting syringe, the one people use for turkeys, and
inject it into the wood. When the rotted section is above you, under
an eave, its hard to daub it on with a brush correctly. After a few
applications you can then apply the miniwax wood putty and paint.