gogmagog wrote:
My mum n dad have a garage attached to their house. It's rather
long, since the guy who built it (previous owner did it himself,
we're told) also extended the kitchen sideways at the same time. So,
it's the same length as the house (25 feet or so). Neighbour says he
used pretty much any bits of chipboard he could find. There seems to
be no incline, since water tends to sit it pools on top. It has a
few leaks, and has once caused water to pour out of a light switch in
the kitchen. I patched that one up, but we're thinking it would be
nice to do something so that we can just forget about it in future. Having
it properly replaced is out of the question - the money will
never be available in their lifetimes. I was wondering if I could
cover it all up with some corrugated sheets, making sure they slope
down to the back, where there is already a gutter. Is this a
reasonable thing to do, or just plain bonkers?

Bonkers.
Unless you get your corrugated sheets and timber for free, but even then
it's unlikely that the chipboard would even support your weight if it has
been soaked for any length of time.

Cheapo solution - use 8X4 sheets of OSB and get it rubberised by a pro