I recently purchased a rowhouse in Baltimore City, which I am getting
ready to fix up as a rental property. Thus, I am looking for a cheap
yet effective option to repair the roof.
Here's the problem -- The original roof is a built up roof. At some
time, probably around 10 years ago, rolled roofing was installed over
the badly dried out and leaking tar. Whoever installed the rolled
roofing was somewhat careless, as they tore or penetrated the roofing
material in several places. This of course allowed water to get
through to the older tar roof, which we have already established was
Over the course of 10 years or so, water slowly leaking in rotted out
the wood plank sheathing in several areas, resulting in a few soft
spots, plus one spot where the roof is sagging badly between the
joists. This sag made a constant puddle which found its way through
the roofing materials and did some damage to the interior of the
I need to fix this roof quickly and inexpensively. The property is in
an area where a 1400 sq ft 4-bedroom rowhome is worth around 55-60k,
so the property simply isn't worth a large financial investment for a
"permanent" repair. My goal is repair it well enough that I will be
able to spread a new layer of cold-app roofing tar from a can every 5
years or so and other than that not worry about it.
Here's the best solution I have come up with, and I would appreciate
opinions on its reliability and effectiveness. I would like to use
pieces of thick plywood screwed down on top of the existing roof to
cover the soft or sagging spots, with the plywood extending out onto
the sections of roof which are still mechanically sound. Then I would
cover the repairs with tar paper, with the tar paper of course
extending past the edge of the plywood by several feet. I would seal
under the edges of the tar paper with roofing tar, then recoat the
entire surface with the cold-app tar.
It seems logical to me that this type of repair would work, but I
would like some thoughts from those more experienced than I am. I
realize that cutting out the soft sections may be a better option, but
this house is almost 100 years old, so I would expect many many layers
of tar built up creating a very thick roof to cut through, and then
the need to build up on top of the plywood to make it the same
thickness of the roof. It seems like just putting plywood right on top
would be just as reliable and significantly less work.
Here are my main concerns:
Is it ok to put a tar roof (from a can) on top of rolled roofing?
Is it ok to do a patch repair like this?
If this repair technique is done well, is it reasonable to expect that
it will not leak?
Sorry about the long post, and I hope to hear back from you with your
thoughts and experiences.