102E: treated damp, resulted in rot, as neighbour’s gutter blocked

This is house that was treated for rising damp but damp continued. The actual root cause was found to be a neighbour’s blocked gutter and downpipe. Rot resulted from this defect not be correctly identified.

Surveyor Tips:

  • Colourless dampness, at base of wall and ceiling – after stain block applied.
  • The monopole camera confirmed suspicions that dampness coming from neighbour’s gutter.
  • Neighbour quick to doubt findings.
  • Rot found in loft.
  • Condensation in kitchen on metal lintel and French doors from drying clothes and cooking.


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There are signs of dampness in the front right-hand corner of the ground floor reception.

The dampness is visible over 1M off the ground.

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The external wall was very damp as measured with the radio-frequency damp meter.

I tested walls for damp with a Protimeter in radio frequency mode. Water reflects radio waves at a set frequency similar to mobile phone shields. Meters can’t differentiate moisture from other dense matter such as metal and concrete. They help trace damp in a normal, homogeneous wall. Readings below 300 REL indicate that a wall is dry below the surface, 999 REL is the limit. These meters are for scanning, mapping and profiling, see surveyor.tips/profile. 

Looking outside we can see you a damp patch in the corner of the wall.

The lower section of the external render looks like it has been disrupted with injection holes used to chemically damp proof – this was later confirmed. Typically chemical damp proofing involves replacement of the original plaster with damp proofers impermeable slurry. This would account for the peculiar shape of the internal dampness. Note the render crack, that should be filled.

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There is a plastic bag on the neighbour’s side splashing rainwater onto the wall. 

Rainwater was pouring off the edge of the gutter onto the plastic bag and from there onto the wall making the wall damper than it would otherwise be. This is not the root cause but has become part of the problem.

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Upstairs in the first floor master bedroom there is dampness on the front wall and adjoining party wall.

Penetrating damp is normally accompanied by a tea bag like stain form of discolouration caused by water passing through brick or timber. I understand stain block has been used to hide darkness in the wall. The colour still visible behind the stain block.

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Using a damp meter, identified a semi-circular area of dampness centred on the corner of the room.

This points to penetrating damp up at the top corner of this room.

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Looking above the corner of the room we can see that there is some rot and mould on the section of roof timber.

I tested the timber for strength and determined that it is still strong. However, if water continues to pour onto the wall and timber, eventually the joist will disintegrate, causing many thousands of pounds worth of damage to the roof.

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I removed a piece of rot from under the joist.
The reverse was mouldy, which show that the fruiting body is longer active.

The fruiting body appears to come from Coniophora puteana, or cellar rot, a brown wet fungus, see surveyor.tips/rot. Rot requires water to grow. Remove the water at source and rot will stop destroying timber.

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The potential for rot extends about 1.5M in from the corner.

There is also surface mould, this is an indication of excess humidity caused from moisture drying from the wet brick. Mould does not cause rot.

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Looking immediately outside at the top of the room we can see dampness on the brick.

This image was taken after the rain had stopped. However I saw the gutters operating during a rainstorm. Water was clearly flowing out of your neighbours gutter onto your wall.

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Looking above we can just about see that the neighbours gutter it’s full of water.

During the rain storm, water was flowing from the top onto the party wall a section of your roof and wall.

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Looking immediately down at the neighbour’s gutter and downpipe we see that the gutter is blocked.

From experience I would guess that it is a tennis ball or similar shape that is blocking your neighbours’ gutter and downpipe.

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A clip on the last section of your gutter has come free.

You can see from this image that your gutter and downpipe is free-flowing. However also note that the clip has come off the final section of your gutter. A small amount of water was leaking from your gutter at this joint. I don’t believe that this is the root cause because it is below the damp timber in your roof. However, it should be clipped back in position and tested to make sure that there is no ongoing gutter leak.

Other matters

That was dampness in the corner of your kitchen below the lintel.

Typically lintels are composed of concrete and metal, and therefore lose heat rapidly when it is cold outside, increasing the risk of condensation.

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When I visited the property on Tuesday morning condensation was visible on the metal of the French doors.

There is clearly excess vapour been produced in the kitchen and/or insufficient ventilation.

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When I returned the second time I found clothes drying in the kitchen.

I also note that there is no externally ducted extractor fan in the kitchen or bathroom.

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