Hi people

Not strictly d.i.y., but I am feeling the need of some background
understanding of brick and guttering and suchlike...

Around 20 August or so, there were a couple of heavy rainstorms, and we
discovered that the guttering at the front of the house had developed a
problem.

There is one two-storey downwards pipe which serves the guttering around
the top of the bay windows of both our house and next door.  The water
from each roof discharges onto the bay windows, so this pipe is supposed
to take all the water from the front half of both roofs, about 16 square
metres per house.  Pipe diameter is maybe about 7cm.

During these storms, water was spilling out of the gutter at or near the
top of the pipe and running down the wall.  It seemed to be overflowing
rather than leaking from a hole.

The rooms just below that gutter (in both houses) then developed damp
plaster in the corner.  I haven't been round next door to look at
theirs, but in ours we've got some bubbles in the wallpaper and a few
faint bits of mould.  Just after the storms there was actually a tiny
puddle along the top of the skirting board.

I got in touch with our local go-up-ladders people but they haven't been
round yet, but meanwhile I've been trying to work out what's actually
gone wrong and what needs to happen to fix it.

Investigations I have made:

Looking at the guttering from above when it was dry.  There are no
obvious broken bits.  (bearing out my impression that the water was
overflowing rather than leaking.)  It isn't blocked in the open part.

Looking at the bottom of the pipe.  I was imagining that there would be
a grating there which might be blocked, and hence be blocking the pipe,
but in fact the pipe seems to go straight into the ground, so no help
there.

Tapping the pipe (about 1m above the ground) to see what sort of noise
it made and how much mass it seemed to have, to see if it seemed to be
full.  I wasn't totally sure, but it seemed to be empty.  (Come to think
of it, I could probably increase my certainty by doing the same with one
I know to be empty, for comparison.  It's a plastic one - I wouldn't
expect to be able to tell like that with a metal one.  The bottom
section is metal though, clearly the remains of an older one.  The
plastic one fits inside the metal one which is probably 3".)

When it rained again the other day, leaning out of the dormer window
above the bay window, to see what the gutter was doing.  It was working
normally.  But that rain was somewhat less heavy than the rainstorms in
August.

Theories:

1.  There _was_ a blockage in the pipe, but it has gone.

2.  There was never a blockage, and it was just that the rain was so
heavy that it exceeded the capacity of the pipe.  However, we have had
heavier rain blowing towards that side of the house in past years
without causing the same problem, so I don't believe this.  (But that's
why I put in the bit about the roof size and the pipe diameter.
Opinions welcome.)

3.  There is a semi-blockage, which slows the flow enough to cause a
problem when the rain gets over a certain rate.

4.  Something I haven't thought of.

Questions:

1.  If the guttering problem has cured itself, or when we do cure it,
how long is it likely to take the wall to dry, and what should we do to
help it?  So far I've just been trying to keep the windows open in that
room as much as possible when the weather's dry.

(This is the aspect of the problem which I'm mostly worried about - I
remember a similar problem where a blocked gutter had been allowed to
drench a wall all winter, and it took a very very long time for the wall
to dry out, and the skirting board got woodworm.  But the drainage at
the bottom of that wall was poor, and it had got wet for much longer
than this one.)

2.  Is it normal for a vertical pipe taking rainwater from a roof to go
straight into the ground?  Or if I dig up the garden there am I likely
to find a grating obscured by leaf mould?

3.  If there's a blockage in the vertical pipe, and no grating, how do
you clear the blockage?  (I'm imagining some kind of slightly flexible
rods from above, but simultaneously worrying that it means taking the
whole thing down)

4.  Where will the underground bit go, and how would we get access to
that if necessary?  (I'm guessing into the same drainage system as the
grid drains in road gutters)  And is the bit under the garden likely to
be the same diameter as the vertical pipe, or would it be bigger so that
any lumpy blockage would flow away if poked along that far?  Or is that
unpredictable and we'd have to dig up the garden to know?

5.  Are "generic roofing people" likely to be able to sort this out, or
do we want someone who specialises in guttering and who'd have
particular bits of equipment?

6.  Any other ideas, or useful things for me to know?

Thanks in advance for all expertise and anecdotal evidence :-)

-- 
      Jennifer      * * * *  original music:  www.single-bass.co.uk *
                    * *  everything else:  www.uncharted-worlds.org *
                    * * * * * * intuition . imagination . integrity *
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