On Friday, November 8, 2019 at 9:03:54 AM UTC-5, wrote:
Hello, my house was built in the 80s and is located in the NE United States. I recently had a handyman in to do some work outside replacing some rotten wood and he said it looks like some corners were cut when the house was built, the builders did not install 'flashing' around the edges of the roof,

You can add drip flashing there, just by sliding it under the shingles.
The shingles should not be nailed that close to the edge.

and the roof doesnt overhang the siding in many places.

?? You mean the shingles don't overhang the edge of the roof enough?
You could install flashing under the shingles there too.



Also he said the house doesn't have a 'membrane' layer, which is is a more recent requirement. As a result water can get behind the siding and cause rot.

Depends on what locations he's talking about. If it's at the lower portion
of the roof, above the gutters, that would only be an issue with ice damming.
That happens when snow melts, but the bottom of the roof is still blocked
with snow and ice and the water backs up. It can run into the house and
cause damage. If you are somewhere that it happens enough, I guess it can
lead to rot too, but water at the interior walls or ceilings is the typical
problem. By code in locations where ice damming occurs, there is supposed
to be a water barrier applied from the bottom edge of the roof up to two
feet above where the roof plane crosses a heated wall.



He thinks that the roof shingles need to be replaced in order to install the flashing.

If it's just flashing at the edges, the answer is no. Even if it was other
flashing, eg step flashing, you could get that in there and only have to
remove and replace the shingles in that area. To install a membrane though,
then IDK. I guess you could just take off shingles from the lower several
feet, then replace. But with any of the work where it gets to replacing
shingles, since the roof is 10 years old, they won't match.



I think the shingles are in pretty good shape. Its not the original roof, but it is at least 10 years old. I dont want to get a new roof if I dont need to. He knows a roofing guy who will take a look, but I plan to get an independent roofer to check as well. Does the bit about flashing sound correct? And can flashing be installed without replacing the whole roof? Thanks

Where exactly is the rot? How extensive? What was the initial problem
that got him involved? If they didn't have the shingles overhang the
roof properly and/or didn't put flashing there, that can easily lead to
the fascia boards on the soffits, behind the gutters rotting.