We have just moved into a flat and some potential damp issues have
come to light from:
- Our own inspection
- The initial home buyer report
- A survey by a damp contractor

As far as I can tell the damp contractor offered no reason as to the
causes (other than a failed DPC). Surprise, surprise, none of the
suggested work remedies the causes of the supposed damp. Their work
would involve DPC injection, replastering, CDM tanking, etc...

However what I would really appreciate is any advice regarding what
the genuine causes are and how I can remedy them. Here's a summary of
the possible problem areas. I’ve included some photos and a summary of
what I think the possible causes are - which of course may be
completely incorrect.

** Rear Left of property **
Some of the plaster is blown here on the rear wall and on the 3rd
party wall. There is no smell of damp in the room.
There is external evidence of rising damp - salty deposits on the
brickwork - see photo below
Damp contractor said there were high meter readings here (I realise a
meter reading doesn't equate to damp)
See photo: http://i51.tinypic.com/jzfq53.jpg

* Possible Causes *
The original DPC has previously been judged (correctly/incorrectly) to
have failed and a new chemically injected DPC has been added. This is
not below the level of the internal floor.
The pebble filled trough has a biggish gap in the corner which may be
allowing water to penetrate.
The two drainage pipes from the trough were very difficult to access
from inside the trough - it seemed that they were covered in very
hardened sand.

* Possible Remedies *
Clear entrances to the copper drainage pipes - done.
Fix up damaged mortar.
Paint a liquid bitumen DPM around edge of trough?
Line the trough with a water proof sheet?


** Rear Right of Property **
Some of the plaster is blown on both sides of the internal wall –
nothing major.
There is no smell of damp in the room
The damp contractor noted high meter readings, claiming there was
"Lateral Penetrating Damp"
See photos: http://i51.tinypic.com/347wnkm.jpg and http://i56.tinypic.com/im13du.jpg

* Possible Causes *
The diagonal section of the guttering had originally fallen out of
place meaning water was discharging directly onto the flat roof, I
have put this back (although it needs fixing properly in the middle as
it’s sagging, which is probably why it fell down in the first place)
The flashing is made of the same material as the flat roof rather than
lead.
The drainage pipes in the pebble filled trough seem a little too high
to be effective, they are at least a centimetre above the base of the
trough.
The raised platform at the back of the property could be bridging the
DPC to the lower rear bedroom?

* Possible Remedies *
Relocate the copper drainage pipes slightly lower
Paint a liquid bitumen DPM around edge of trough
Line the trough with a waterproof sheet?

Are there any causes which I have incorrectly identified ?

Any help/advice/criticism would be gratefully received.

Charlie

On Jul 6, 7:17*pm, Charlie wrote:
We have just moved into a flat and some potential damp issues have
come to light from:
- Our own inspection
- The initial home buyer report
- A survey by a damp contractor

As far as I can tell the damp contractor offered no reason as to the
causes (other than a failed DPC). Surprise, surprise, none of the
suggested work remedies the causes of the supposed damp. *Their work
would involve DPC injection, replastering, CDM tanking, etc...

However what I would really appreciate is any advice regarding what
the genuine causes are and how I can remedy them. Here's a summary of
the possible problem areas. I’ve included some photos and a summary of
what I think the possible causes are - which of course may be
completely incorrect.

** Rear Left of property **
Some of the plaster is blown here on the rear wall and on the 3rd
party wall. *There is no smell of damp in the room.
There is external evidence of rising damp - salty deposits on the
brickwork - see photo below
Damp contractor said there were high meter readings here (I realise a
meter reading doesn't equate to damp)
See photo:http://i51.tinypic.com/jzfq53.jpg

* Possible Causes *
The original DPC has previously been judged (correctly/incorrectly) to
have failed and a new chemically injected DPC has been added. *This is
not below the level of the internal floor.
The pebble filled trough has a biggish gap in the corner which may be
allowing water to penetrate.
The two drainage pipes from the trough were very difficult to access
from inside the trough - it seemed that they were covered in very
hardened sand.

* Possible Remedies *
Clear entrances to the copper drainage pipes - done.
Fix up damaged mortar.
Paint a liquid bitumen DPM around edge of trough?
Line the trough with a water proof sheet?

** Rear Right of Property **
Some of the plaster is blown on both sides of the internal wall –
nothing major.
There is no smell of damp in the room
The damp contractor noted high meter readings, claiming there was
"Lateral Penetrating Damp"
See photos:http://i51.tinypic.com/347wnkm.jpgan...com/im13du.jpg

* Possible Causes *
The diagonal section of the guttering had originally fallen out of
place meaning water was discharging directly onto the flat roof, I
have put this back (although it needs fixing properly in the middle as
it’s sagging, which is probably why it fell down in the first place)
The flashing is made of the same material as the flat roof rather than
lead.
The drainage pipes in the pebble filled trough seem a little too high
to be effective, they are at least a centimetre above the base of the
trough.
The raised platform at the back of the property could be bridging the
DPC to the lower rear bedroom?

* Possible Remedies *
Relocate the copper drainage pipes slightly lower
Paint a liquid bitumen DPM around edge of trough
Line the trough with a waterproof sheet?

Are there any causes which I have incorrectly identified ?

Any help/advice/criticism would be gratefully received.

Charlie

Without being there and having a good look round - I'm guessing - but:

Fixing the obvious gutter leak was an excellent first move - be sure
to deal with any other obviously "wrong" things with the drainage like
that promptly.

The guttering and downpipes arrangements around the property looks
"complicated". It could be that other parts can't cope with heavy
rainfall, and tend to spill over sometimes. I would look to modify the
drainage to ensure everything flow freely and has lots of capacity,
and nothing leaks. Also check "where" it drains to - probe with a
hosepipe - soakaways or public drainage? Does it all work - no
blockages or poor flows?

The brickwork around the pebble filled troughs is obviously newer than
the original brickwork - and the levels inside look like they
correspond to half way up the walls inside.

I would dig out the contents (simple, but hard work!), and maybe
remove those new walls as well. Reason being - your house was probably
built correctly in the first place - but later modifications (may)
have "broken" it.

All damp problems usually come down to either ill-considered
modifications, or lack of maintenance.

Good design allows everything to drain freely - including run-off from
walls, away from the building - and for the residue to be windswept
and dry quickly. That new brickwork trough looks suspicious to me in
that respect.

The damp tester is an idiot. They usually are. They all usually say
"failed DPC" as well. He wants to sell you a proprietary damp
treatment - rather than fix the underlying cause. A similar idiot has
already tried injection treatment - and clearly hasn't fixed the
problem.

Common causes are - penetrating (e.g. a heap of stuff outside that
bridges the dampcourse or your downpipes), leaks (water/sewage pipes),
condensation (poor ventilation), and rising (least common).

On Wed, 6 Jul 2011 11:17:11 -0700 (PDT), Charlie wrote:

See photo: http://i51.tinypic.com/jzfq53.jpg

* Possible Causes *
The original DPC has previously been judged (correctly/incorrectly) to
have failed and a new chemically injected DPC has been added. This is
not below the level of the internal floor.
The pebble filled trough has a biggish gap in the corner which may be
allowing water to penetrate.
The two drainage pipes from the trough were very difficult to access
from inside the trough - it seemed that they were covered in very
hardened sand.

First thought that went through my head when I saw the marks on the
wall a pebbled filled enclosure was "that isn't draining". Think I
clear everything out of that make sure the drains are clear and that
no water can remains standing in it anywhere. Then put back the
pebbles making sure that the drains don't get blocked.

** Rear Right of Property **

The broken down spout (guttering is the trough that runs along the
edge of the roof) wouldn't help. I'd check the conditionof the flat
roof particularly along the wall. Our flat roof was torched on and
also has the felt material bent up a parapet wall. This was torched
on but the stiffness of the felt and thermal cycling has pulled it
away leaving a gaping chasm to let in rain, snow etc...

Pebble trough, as the other one. Make sure it fully drains.

On the 3rd phot a couple of the injection holes haven't been filled.

I see lots of washing in the lower room, condensation might be the
cause of some of the damp.

--
Cheers
Dave.

Charlie wrote:
We have just moved into a flat and some potential damp issues have
come to light from:
- Our own inspection
- The initial home buyer report
- A survey by a damp contractor

As far as I can tell the damp contractor offered no reason as to the
causes (other than a failed DPC). Surprise, surprise, none of the
suggested work remedies the causes of the supposed damp. Their work
would involve DPC injection, replastering, CDM tanking, etc...

However what I would really appreciate is any advice regarding what
the genuine causes are and how I can remedy them. Here's a summary of
the possible problem areas. I’ve included some photos and a summary of
what I think the possible causes are - which of course may be
completely incorrect.

** Rear Left of property **
Some of the plaster is blown here on the rear wall and on the 3rd
party wall. There is no smell of damp in the room.
There is external evidence of rising damp - salty deposits on the
brickwork - see photo below
Damp contractor said there were high meter readings here (I realise a
meter reading doesn't equate to damp)
See photo: http://i51.tinypic.com/jzfq53.jpg

* Possible Causes *
The original DPC has previously been judged (correctly/incorrectly) to
have failed and a new chemically injected DPC has been added. This is
not below the level of the internal floor.
The pebble filled trough has a biggish gap in the corner which may be
allowing water to penetrate.
The two drainage pipes from the trough were very difficult to access
from inside the trough - it seemed that they were covered in very
hardened sand.

* Possible Remedies *
Clear entrances to the copper drainage pipes - done.
Fix up damaged mortar.
Paint a liquid bitumen DPM around edge of trough?
Line the trough with a water proof sheet?


** Rear Right of Property **
Some of the plaster is blown on both sides of the internal wall –
nothing major.
There is no smell of damp in the room
The damp contractor noted high meter readings, claiming there was
"Lateral Penetrating Damp"
See photos: http://i51.tinypic.com/347wnkm.jpg and http://i56.tinypic.com/im13du.jpg

* Possible Causes *
The diagonal section of the guttering had originally fallen out of
place meaning water was discharging directly onto the flat roof, I
have put this back (although it needs fixing properly in the middle as
it’s sagging, which is probably why it fell down in the first place)
The flashing is made of the same material as the flat roof rather than
lead.
The drainage pipes in the pebble filled trough seem a little too high
to be effective, they are at least a centimetre above the base of the
trough.
The raised platform at the back of the property could be bridging the
DPC to the lower rear bedroom?

* Possible Remedies *
Relocate the copper drainage pipes slightly lower
Paint a liquid bitumen DPM around edge of trough
Line the trough with a waterproof sheet?

Are there any causes which I have incorrectly identified ?

Any help/advice/criticism would be gratefully received.

As the others have said, but I'd also be looking *very* closely at
what's lining the pebble beds. If they're not draining properly, the bed
will fill with water, and if the waterproof lining on the wall of the
flat is defective, it's like having a pool outside the wall. Take the
pebbles out, take off as much of the original lining as you can, make
good all the mortar joints in the area, and use bituminous damp proofing
to seal the brickwork up to about 100mm above the level of the pebbles,
then apply something to protect the bitumen. If you do it right, you
could replace the pebble beds with small ponds with good results, apart
from the possibility of the occasional drowned child. I'd guess it's a
problem of quite long standing, as an attempt to cure it has been made
by injecting a chemical DPC through the mortar filled holes in the
bricks. Above the floor level, too.....

Is it clay soil? Weather related movement could have caused the damage
shown in the first picture. I can also see the very degraded remains of
what could have been the original damp proofing put in when the raised
beds were added.

--
Tciao for Now!

John.

Dave,

Thanks for your post, I agree with what you say, only a couple of
points.

** Rear Right of Property **

The broken down spout (guttering is the trough that runs along the
edge of the roof) wouldn't help. I'd check the conditionof the flat
roof particularly along the wall.

To be honest it looks OK, the material is neatly tucked in and the
cement all present and correct

On the 3rd photo a couple of the injection holes haven't been filled.

Yes agreed - I will fill those in

I see lots of washing in the lower room, condensation might be the
cause of some of the damp.

Well spotted :-) We've just moved in so I'm not sure this is was the
original cause

Thanks again for your comments

Charlie

Dom,

The guttering and downpipes arrangements around the property looks
"complicated". It could be that other parts can't cope with heavy
rainfall, and tend to spill over sometimes. I would look to modify the
drainage to ensure everything flow freely and has lots of capacity,
and nothing leaks. Also check "where" it drains to - probe with a
hosepipe - soakaways or public drainage? *Does it all work - no
blockages or poor flows?

Good idea I'll also check when we next have a heavy downpour to what's
going on.


The brickwork around the pebble filled troughs is obviously newer than
the original brickwork - and the levels inside look like they
correspond to half way up the walls inside.

Yes it is newer

I would dig out the contents (simple, but hard work!), and maybe
remove those new walls as well. Reason being - your house was probably
built correctly in the first place - but later modifications (may)
have "broken" it.

I had a horrible feeling someone might say that. That's going to be a
simple but big job,
presumably I'll need to replace the steps down to the garden as well?

Thanks for all the rest of your comments - I really appreciate them.
They make a lot of sense.

Charlie

On Wed, 6 Jul 2011 14:16:38 -0700 (PDT), Charlie wrote:

I would dig out the contents (simple, but hard work!), and maybe
remove those new walls as well. Reason being - your house was
probably
built correctly in the first place - but later modifications (may)
have "broken" it.

I had a horrible feeling someone might say that. That's going to be a
simple but big job, presumably I'll need to replace the steps down to
the garden as well?

The steps look orginal with the two walls built onto them. Some of
the paving making up the steps looks a bit broken/uneven. I think you
only have to remove the side walls down to the steps and the two
front ones. Then worry about what is filling up most of the space in
those troughs, if the drain pipes are at the top of that fill.

Some form of rails each side might be useful addition. It looks like
quite drop from the steps to ground level.

--
Cheers
Dave.

On Wed, 6 Jul 2011 11:17:11 -0700 (PDT), Charlie
wrote:

We have just moved into a flat and some potential damp issues have
come to light from:
- Our own inspection
- The initial home buyer report
- A survey by a damp contractor

It looks to be an old building without a cavity wall. Has it has had
double glazing fitted without trickle ventilators? Single brick walls
have poor insulation and are inherently damp. They rely upon a lot of
air changes to prevent internal damp showing. Fitting double glazing
(especially with no ventilation at all) or even new well fitting
windows stops adequate ventilation in the building and also moves the
cold spots in rooms from the windows (where they used to be) to the
walls.

Before looking outside make sure the problem isn't actually the far
more common one of condensation.

On Jul 6, 7:17*pm, Charlie wrote:
We have just moved into a flat and some potential damp issues have
come to light from:
- Our own inspection
- The initial home buyer report
- A survey by a damp contractor

As far as I can tell the damp contractor offered no reason as to the
causes (other than a failed DPC). Surprise, surprise, none of the
suggested work remedies the causes of the supposed damp. *Their work
would involve DPC injection, replastering, CDM tanking, etc...

However what I would really appreciate is any advice regarding what
the genuine causes are and how I can remedy them. Here's a summary of
the possible problem areas. I’ve included some photos and a summary of
what I think the possible causes are - which of course may be
completely incorrect.

** Rear Left of property **
Some of the plaster is blown here on the rear wall and on the 3rd
party wall. *There is no smell of damp in the room.
There is external evidence of rising damp - salty deposits on the
brickwork - see photo below
Damp contractor said there were high meter readings here (I realise a
meter reading doesn't equate to damp)
See photo:http://i51.tinypic.com/jzfq53.jpg

* Possible Causes *
The original DPC has previously been judged (correctly/incorrectly) to
have failed and a new chemically injected DPC has been added. *This is
not below the level of the internal floor.
The pebble filled trough has a biggish gap in the corner which may be
allowing water to penetrate.
The two drainage pipes from the trough were very difficult to access
from inside the trough - it seemed that they were covered in very
hardened sand.

* Possible Remedies *
Clear entrances to the copper drainage pipes - done.
Fix up damaged mortar.
Paint a liquid bitumen DPM around edge of trough?
Line the trough with a water proof sheet?

** Rear Right of Property **
Some of the plaster is blown on both sides of the internal wall –
nothing major.
There is no smell of damp in the room
The damp contractor noted high meter readings, claiming there was
"Lateral Penetrating Damp"
See photos:http://i51.tinypic.com/347wnkm.jpgan...com/im13du.jpg

* Possible Causes *
The diagonal section of the guttering had originally fallen out of
place meaning water was discharging directly onto the flat roof, I
have put this back (although it needs fixing properly in the middle as
it’s sagging, which is probably why it fell down in the first place)
The flashing is made of the same material as the flat roof rather than
lead.
The drainage pipes in the pebble filled trough seem a little too high
to be effective, they are at least a centimetre above the base of the
trough.
The raised platform at the back of the property could be bridging the
DPC to the lower rear bedroom?

* Possible Remedies *
Relocate the copper drainage pipes slightly lower
Paint a liquid bitumen DPM around edge of trough
Line the trough with a waterproof sheet?

Are there any causes which I have incorrectly identified ?

Any help/advice/criticism would be gratefully received.

Charlie

Yes, evidence of damp near ground level is not evidence of rising
damp. In the overwhelming majority of cases its one of the other
causes, such as condensation or splash.

DPC failure is unlikely to have anything to do with anything. Almost
all houses built with no dpc functioned jsut fine, dpcs are more
backup devices than functionally necessary.

A big container full of wet material against the all is jsut asking
for trouble. Thre are various other possible causes that I dont know
whether they'd apply here, its just not possible to look around and
check it all out remotely.


NT

On Jul 6, 9:42*pm, John Williamson
wrote:
Charlie wrote:
We have just moved into a flat and some potential damp issues have
come to light from:
- Our own inspection
- The initial home buyer report
- A survey by a damp contractor

As far as I can tell the damp contractor offered no reason as to the
causes (other than a failed DPC). Surprise, surprise, none of the
suggested work remedies the causes of the supposed damp. *Their work
would involve DPC injection, replastering, CDM tanking, etc...

However what I would really appreciate is any advice regarding what
the genuine causes are and how I can remedy them. Here's a summary of
the possible problem areas. I ve included some photos and a summary of
what I think the possible causes are - which of course may be
completely incorrect.

** Rear Left of property **
Some of the plaster is blown here on the rear wall and on the 3rd
party wall. *There is no smell of damp in the room.
There is external evidence of rising damp - salty deposits on the
brickwork - see photo below
Damp contractor said there were high meter readings here (I realise a
meter reading doesn't equate to damp)
See photo:http://i51.tinypic.com/jzfq53.jpg

* Possible Causes *
The original DPC has previously been judged (correctly/incorrectly) to
have failed and a new chemically injected DPC has been added. *This is
not below the level of the internal floor.
The pebble filled trough has a biggish gap in the corner which may be
allowing water to penetrate.
The two drainage pipes from the trough were very difficult to access
from inside the trough - it seemed that they were covered in very
hardened sand.

* Possible Remedies *
Clear entrances to the copper drainage pipes - done.
Fix up damaged mortar.
Paint a liquid bitumen DPM around edge of trough?
Line the trough with a water proof sheet?

** Rear Right of Property **
Some of the plaster is blown on both sides of the internal wall
nothing major.
There is no smell of damp in the room
The damp contractor noted high meter readings, claiming there was
"Lateral Penetrating Damp"
See photos:http://i51.tinypic.com/347wnkm.jpgan...com/im13du.jpg

* Possible Causes *
The diagonal section of the guttering had originally fallen out of
place meaning water was discharging directly onto the flat roof, I
have put this back (although it needs fixing properly in the middle as
it s sagging, which is probably why it fell down in the first place)
The flashing is made of the same material as the flat roof rather than
lead.
The drainage pipes in the pebble filled trough seem a little too high
to be effective, they are at least a centimetre above the base of the
trough.
The raised platform at the back of the property could be bridging the
DPC to the lower rear bedroom?

* Possible Remedies *
Relocate the copper drainage pipes slightly lower
Paint a liquid bitumen DPM around edge of trough
Line the trough with a waterproof sheet?

Are there any causes which I have incorrectly identified ?

Any help/advice/criticism would be gratefully received.

As the others have said, but I'd also be looking *very* closely at
what's lining the pebble beds. If they're not draining properly, the bed
will fill with water, and if the waterproof lining on the wall of the
flat is defective, it's like having a pool outside the wall.

Agreed, it looks like I've got swimming pools leaking into my
house :-)

Take the
pebbles out, take off as much of the original lining as you can, make
good all the mortar joints in the area, and use bituminous damp proofing
to seal the brickwork up to about 100mm above the level of the pebbles,
then apply something to protect the bitumen. If you do it right, you
could replace the pebble beds with small ponds with good results, apart
from the possibility of the occasional drowned child.

This seems like a straightforward solution

I'd guess it's a
problem of quite long standing, as an attempt to cure it has been made
by injecting a chemical DPC through the mortar filled holes in the
bricks. Above the floor level, too.....

Agreed - probably the previous owner had a damp contractor in when he
bought the place
and they told him he needed an injected DPC

Is it clay soil? Weather related movement could have caused the damage
shown in the first picture. I can also see the very degraded remains of
what could have been the original damp proofing put in when the raised
beds were added.

Yes you are right you can see this one of the photos quite clearly.

Thanks for all your advice


--
Tciao for Now!

John.

On Jul 7, 9:40*am, NT wrote:
On Jul 6, 7:17*pm, Charlie wrote:









We have just moved into a flat and some potential damp issues have
come to light from:
- Our own inspection
- The initial home buyer report
- A survey by a damp contractor

As far as I can tell the damp contractor offered no reason as to the
causes (other than a failed DPC). Surprise, surprise, none of the
suggested work remedies the causes of the supposed damp. *Their work
would involve DPC injection, replastering, CDM tanking, etc...

However what I would really appreciate is any advice regarding what
the genuine causes are and how I can remedy them. Here's a summary of
the possible problem areas. I’ve included some photos and a summary of
what I think the possible causes are - which of course may be
completely incorrect.

** Rear Left of property **
Some of the plaster is blown here on the rear wall and on the 3rd
party wall. *There is no smell of damp in the room.
There is external evidence of rising damp - salty deposits on the
brickwork - see photo below
Damp contractor said there were high meter readings here (I realise a
meter reading doesn't equate to damp)
See photo:http://i51.tinypic.com/jzfq53.jpg

* Possible Causes *
The original DPC has previously been judged (correctly/incorrectly) to
have failed and a new chemically injected DPC has been added. *This is
not below the level of the internal floor.
The pebble filled trough has a biggish gap in the corner which may be
allowing water to penetrate.
The two drainage pipes from the trough were very difficult to access
from inside the trough - it seemed that they were covered in very
hardened sand.

* Possible Remedies *
Clear entrances to the copper drainage pipes - done.
Fix up damaged mortar.
Paint a liquid bitumen DPM around edge of trough?
Line the trough with a water proof sheet?

** Rear Right of Property **
Some of the plaster is blown on both sides of the internal wall –
nothing major.
There is no smell of damp in the room
The damp contractor noted high meter readings, claiming there was
"Lateral Penetrating Damp"
See photos:http://i51.tinypic.com/347wnkm.jpgan...com/im13du.jpg

* Possible Causes *
The diagonal section of the guttering had originally fallen out of
place meaning water was discharging directly onto the flat roof, I
have put this back (although it needs fixing properly in the middle as
it’s sagging, which is probably why it fell down in the first place)
The flashing is made of the same material as the flat roof rather than
lead.
The drainage pipes in the pebble filled trough seem a little too high
to be effective, they are at least a centimetre above the base of the
trough.
The raised platform at the back of the property could be bridging the
DPC to the lower rear bedroom?

* Possible Remedies *
Relocate the copper drainage pipes slightly lower
Paint a liquid bitumen DPM around edge of trough
Line the trough with a waterproof sheet?

Are there any causes which I have incorrectly identified ?

Any help/advice/criticism would be gratefully received.

Charlie

Yes, evidence of damp near ground level is not evidence of rising
damp. In the overwhelming majority of cases its one of the other
causes, such as condensation or splash.

DPC failure is unlikely to have anything to do with anything. Almost
all houses built with no dpc functioned jsut fine, dpcs are more
backup devices than functionally necessary.

A big container full of wet material against the all is jsut asking
for trouble. Thre are various other possible causes that I dont know
whether they'd apply here, its just not possible to look around and
check it all out remotely.

Agreed, I'll fix this up as per John Williamson's suggestions


NT

On Jul 7, 9:40*am, NT wrote:
On Jul 6, 7:17*pm, Charlie wrote:









We have just moved into a flat and some potential damp issues have
come to light from:
- Our own inspection
- The initial home buyer report
- A survey by a damp contractor

As far as I can tell the damp contractor offered no reason as to the
causes (other than a failed DPC). Surprise, surprise, none of the
suggested work remedies the causes of the supposed damp. *Their work
would involve DPC injection, replastering, CDM tanking, etc...

However what I would really appreciate is any advice regarding what
the genuine causes are and how I can remedy them. Here's a summary of
the possible problem areas. I’ve included some photos and a summary of
what I think the possible causes are - which of course may be
completely incorrect.

** Rear Left of property **
Some of the plaster is blown here on the rear wall and on the 3rd
party wall. *There is no smell of damp in the room.
There is external evidence of rising damp - salty deposits on the
brickwork - see photo below
Damp contractor said there were high meter readings here (I realise a
meter reading doesn't equate to damp)
See photo:http://i51.tinypic.com/jzfq53.jpg

* Possible Causes *
The original DPC has previously been judged (correctly/incorrectly) to
have failed and a new chemically injected DPC has been added. *This is
not below the level of the internal floor.
The pebble filled trough has a biggish gap in the corner which may be
allowing water to penetrate.
The two drainage pipes from the trough were very difficult to access
from inside the trough - it seemed that they were covered in very
hardened sand.

* Possible Remedies *
Clear entrances to the copper drainage pipes - done.
Fix up damaged mortar.
Paint a liquid bitumen DPM around edge of trough?
Line the trough with a water proof sheet?

** Rear Right of Property **
Some of the plaster is blown on both sides of the internal wall –
nothing major.
There is no smell of damp in the room
The damp contractor noted high meter readings, claiming there was
"Lateral Penetrating Damp"
See photos:http://i51.tinypic.com/347wnkm.jpgan...com/im13du.jpg

* Possible Causes *
The diagonal section of the guttering had originally fallen out of
place meaning water was discharging directly onto the flat roof, I
have put this back (although it needs fixing properly in the middle as
it’s sagging, which is probably why it fell down in the first place)
The flashing is made of the same material as the flat roof rather than
lead.
The drainage pipes in the pebble filled trough seem a little too high
to be effective, they are at least a centimetre above the base of the
trough.
The raised platform at the back of the property could be bridging the
DPC to the lower rear bedroom?

* Possible Remedies *
Relocate the copper drainage pipes slightly lower
Paint a liquid bitumen DPM around edge of trough
Line the trough with a waterproof sheet?

Are there any causes which I have incorrectly identified ?

Any help/advice/criticism would be gratefully received.

Charlie

Yes, evidence of damp near ground level is not evidence of rising
damp. In the overwhelming majority of cases its one of the other
causes, such as condensation or splash.

DPC failure is unlikely to have anything to do with anything. Almost
all houses built with no dpc functioned jsut fine, dpcs are more
backup devices than functionally necessary.

A big container full of wet material against the all is jsut asking
for trouble. Thre are various other possible causes that I dont know
whether they'd apply here, its just not possible to look around and
check it all out remotely.

NT

Agreed, I'll fix this up as per John Williamson's suggestions

Agreed, it looks like I've got swimming pools leaking into my
house :-)
Take the
pebbles out, take off as much of the original lining as you can, make
good all the mortar joints in the area, and use bituminous damp proofing
to seal the brickwork up to about 100mm above the level of the pebbles,
then apply something to protect the bitumen. If you do it right, you
could replace the pebble beds with small ponds with good results, apart
from the possibility of the occasional drowned child.

This seems like a straightforward solution
I'd guess it's a
problem of quite long standing, as an attempt to cure it has been made
by injecting a chemical DPC through the mortar filled holes in the
bricks. Above the floor level, too.....

Agreed - probably the previous owner had a damp contractor in when he
bought the place
and they told him he needed an injected DPC
Is it clay soil? Weather related movement could have caused the damage
shown in the first picture. I can also see the very degraded remains of
what could have been the original damp proofing put in when the raised
beds were added.

Yes you are right you can see this one of the photos quite clearly.
Thanks for all your advice