Damp meter reading high moisture - help!!

[dryingout]

Had a leak few weeks ago which insurance are helping sort out.
The team who are drying out the place come back every week to take moisture readings.
These seem to vary considerably and go up or down.

Today they said that one of my walls which doesn't feel wet at all, doesn't look wet is reading 90% and 50% moisture levels in places up to 6ft high !

This is crazy surly?

They are telling me they are suggesting to the insurers that the room needs tanking.
(Solid no cavity brick built 1900's terrace)

The wall that has the high reading is internal wall too!

Wall Damp Meter Readers are notoriously inaccurate especially in period properties. The internet is awash with explanations as to why this is.

If there is no visible evidence of damp, it probably isn't damp. Ask your insurance company to instruct a specialist in dealing with period properties for at least a second opinion before tanking.

Is this in a basement? If not, might be worth asking the 'team' why they think there is damp in the place they are detecting it. What is their view of the cause?

They also mentioned about salts and that the walls need anti salt treatment spray applied to walls first

Thank you.
It's not a basement.
In fact I live as high above seal level as possible and the ground levels surrounding the house are at the correct level and drainage is good.
The subfloor ventilation seems fine too.

Damp Meters work by measuring the electrical conductivity of a material (water conducts water so higher readings are recorded in damp materials than in dry materials).

This means that they also record high readings where other conductors are present in walls (e.g. - some stone naturally contains metal elements and bricks/blocks have been formed using waste products from furnaces, etc which also contain metal elements).

As an example, I surveyed a property recently where a 'damp specialist' had diagnosed high levels of damp behind a fixed mirror. I had to explain to him that his meter was recording the metal in the foil on the rear of the mirror. He wouldn't believe me until I showed him that his meter recorded the same levels on any mirror he chose to check.

Damp meters are a tool which should be used by people who understand building pathology - otherwise they are useless.
The salts they mention are salts which are inherent in the building materials - the flood water brings them to the surface and when the water evaporates the salts are left behind - these are often hygroscopic (meaning they absorb moisture from the air).

I would be very aware that the company who is highlighting this damp is effectively writing their own cheques by recommending tanking, etc.

Chemical DPCs, modern plasters and tanking systems can often actually damage older properties by sealing the surfaces and preventing the building fabric from 'breathing'.

I would recommend that you employ (or the insurer does) a chartered building surveyor with experience in older properties.

hope this helps