Damp on internal wall

Hi All,
I moved into a new house and bought a device to measure moisture level of the walls and all the walls around the house are good except just one.
with_damp_inside.jpg (116.02 KiB) Not viewed yet

In the middle point I am getting moisture level of almost 56%. I went up every 20cm and moisture level goes down and then up again to 27%.
Also from the bottom middle point I went right by 50cm and moisture level was still 52% but then I went another 50cm and moisture level went down to 24%.
I did the same going left but moisture level was not changing at the bottom.
Both right and left but at the height of 120cm moisture level is at normal level that is 19%.
Then I decided to go outside to see how moisture level is and here is a photo how it looks like outside:
with_damp_outside.jpg (383 KiB) Not viewed yet
At the middle point 2 bricks above DPC moisture level is 34% but 4 bricks above DPC is 14%.
I tested 50cm left one brick below and above DPC and moisture level was 37% and 31%
Also testing 50cm right 2 bricks above DPC and moisture level was 15%.
1) I wonder what could cause internal wall to be damp? Can it be caused by waste water pipe outside of it?
2) Also why inside wall is more wet than outside?
3) Why outside bricks above DPC are wet? I thoght DPC is supposed to protect them.
4) Any suggestions how to fix wet wall?
Also note that this was a kitchen once and got converted to a bedroom.

Check those gutters and drains first.

If there's no actual sign of damp or damage then don't worry about it.

The moisture measurements are a bit dubious at the best of times.

Debris in the bottom of the wall cavity? That can cause a band of damp along the base of the wall as the debris can bridge the damp proof course. Especially if the wall is also getting soaked by a leaking gutter.

You are not measuring damp, and your walls don't appear to be damp.

You are measuring conductivity of surface moisture (aka condensation) and it does read higher on cooler walls, and that is not indicative of the walls being damp or there being a problem.

And be aware that your damp meter is calibrated for and intended only for use on bare timber.

^woody^ said:

You are not measuring damp, and your walls don't appear to be damp.

You are measuring conductivity of surface moisture (aka condensation) and it does read higher on cooler walls, and that is not indicative of the walls being damp or there being a problem.

And be aware that your damp meter is calibrated for and intended only for use on bare timber.

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So why would isolated patches of the wall be cooler in September when the internal and external temperatures are similar? Wouldn't be because the temperature is reduced by evaporating moisture from rising or penetrating damp would it?

I don't understand why people get their knickers in such a twist about "damp meters". They are just a tool to identify the pattern of areas of increased electrical conductivity exactly how the OP has done it. There is clearly something going on in that wall and now further investigations are required to identify the cause. Given the pattern of the readings I would be very surprised if it turned out to be condensation.

wessex101 said:

So why would isolated patches of the wall be cooler in September when the internal and external temperatures are similar? Wouldn't be because the temperature is reduced by evaporating moisture from rising or penetrating damp would it?

I don't understand why people get their knickers in such a twist about "damp meters". They are just a tool to identify the pattern of areas of increased electrical conductivity exactly how the OP has done it. There is clearly something going on in that wall and now further investigations are required to identify the cause. Given the pattern of the readings I would be very surprised if it turned out to be condensation.

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The edges - bottom, sides and top of any wall can vary in surface temperature to the inner area due to thermal conductivity of the structure (adjacent walls, floor ceiling), natural air currents, direction/orientation, and other factors.

Cooler walls = lower dew points and then surface condensation. And that does nor mean condensation like streaming down the windows, but just air condensing and the slight moisture being absorbed into the permeable surface, just like every absorbent material contains some moisture if exposed to air.

That's why you don't just put a meter on a wall and cry "DAMP!"

Swwils said:

Check those gutters and drains first.

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That was my first reaction. Just replace underground drains. But I am not sure why wall just under the window is 27% but a few feet down it is 19%?

George_engineer said:

If there's no actual sign of damp or damage then don't worry about it.

The moisture measurements are a bit dubious at the best of times.

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Hm.. I checked the whole house and everywhere is fine just this wall is suspicious.

wessex101 said:

Debris in the bottom of the wall cavity? That can cause a band of damp along the base of the wall as the debris can bridge the damp proof course. Especially if the wall is also getting soaked by a leaking gutter.

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Would I need to remove a few bricks of the wall to check that? Not sure that explains reading just under the window at 27%.

^woody^ said:

And be aware that your damp meter is calibrated for and intended only for use on bare timber.

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How do you know that? I configured it to masonry on the damp meter? Also I am concerned more about reative readings other than absolute what I am more concerned about.

If there's no sign of damp or condensation or damage (dusty paint flaky paint, ropey skirtingboards, damp smell) then why are you spending time on this?

There's a million potential reasons why there's a variable conductivity there.

If there's no damage or visible sign (beyond probing with a meter) - is there a problem?

EugeneKR said:

Would I need to remove a few bricks of the wall to check that? Not sure that explains reading just under the window at 27%.

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I would experiment with one of those cheap borescope cameras you can plug in to your phone before you started cutting bricks out.

Regarding the reading under the window, that could be a secondary issue. Check the gutter isn't leaking then investigate the condition of the tiled window sill and sealant along the bottom of the window.