You probably would not! Newer motorhomes are coming with a one-piece,
butyl rubber roof. It comes in various lengths and is applied with a
special mastic. Once sealed it can be coated/painted/treated with
special stuff made for butyl to preserve it. It can last 15-20 years
or so if properly cared for, so I hear. On the other hand, I have seen
many that were beginning to delaminate/bubble. We were parked next to
a beautiful DP and when I got up on my roof to take some panoramic
pics I counted five or six bubbles in it. They are easy to install for
the manufacturer and a replacement for the owner will run about +/-
$800-900 USD for the materials, depending on length and width, etc.

If I were to go that route I would consider a one-piece aluminum sheet
roof. Last I checked, aluminum does not dry out or rot!  ;-)

Speaking of roofs.... I finished prepping mine today for coating! I
have about 60 hours of labor undoing what the idiots did with the
fibered mastic. And then I spent quite a few hours repairing what a PO
did- when there was a leak they tightened screws until they stripped,
then when it leaked again they installed larger screws, and when those
stripped or leaked they drilled more holes and installed more screws.
I was able to get enough of them to bite using plastic screw anchors
and used enough butyl to hold me for a year or two (or more), but
there is one corner that will need a fiberglass mat patch to give the
screws a place to bit. Without pulling off cabinets in the interior
there is no way to get to the back of the panel to add material for
the screws to hold on to from the inside.

While I was at it I also routed the antenna lead for the Winegard
correctly (through the base of the mount). They had it draped over to
the corner of the roof and through a drilled hole. They covered the
hole with a flat piece of aluminum with a hump to fit the wire, and
then used four screws to hold it to the roof with butyl underneath and
fibered roof mastic over all that. Of course, this was in a corner
where water gathers, and you can guess the rest. Not only was the
lead-in unsightly, it was begging to catch a branch and rip itself out
of the roof. They also used a coax connector mid-wire which is not
supposed to be done because of the signal amplifier.

Also installed the new black-water-tank/toilet roof vent. The old one
was just the vent base with a cap, but there was no riser off the vent
pipe. It ended just below roof level with a gap between the pipe and
the roof which could allow fumes into the motor home.

Some people just shouldn't own tools! And the owners of the shop that
did this roof job should keep their hands in their pockets and not use
any tools in there, either!  Idiots!!

TIP: when patching roofs (or anything else) you should not place a
hard or stiff mastic in areas that will flex and NEVER over surfaces
coated with butyl or any other non-hardening or highly flexible
sealant. Rubbery goes ON TOP OF stiff stuff!

But at least the interior will be dry now when it rains! I hope...

       Randy "" G.
http://www.EspressoMyEspresso.com