Can you have damp without any visible signs

Biscuit23

Hello everyone i am hoping someone can help me. We are selling our home built 1880. Our buyers surveyor has said there is some damp downstairs and we are really surprised. They now want a damp specialist but we have checked and there is no bubbling paint, loose plaster, wet marks,mould or damp smell anywhere. Can you really have a bad damp issue and have no internal signs? We bought a damp meter and the underfloor wood joists measure 17 to 18% and the we have got 2 wall on 7 and 8% which i know is higher than normal but could we have some minor damp which hasnt affected or damaged internal walls?we are really anxious and confused.

DRP

if a tree falls in the forest and no one is around to hear it ... does it make a noise?

From the specialist damp survey of our c1880 terrace:

Protimeter conductivity meter
This meter measures the conductivity of the base material it is being placed against and is a useful non-destructive tool providing helpful information when used correctly for assessing possible underlying damp and moisture content of timber. When used to record conductivity of masonry and cement-based materials the readings received are not measuring quantitative moisture levels, the meter is measuring the electrical resistance of the underlying material it’s being placed against, producing a theoretical measurement which is referred to as wood moisture equivalent or WME %.
When used on the timber the readings recorded are moisture content relative.
Care must be taken interpreting the readings when using these types of meters, contaminants within plasterwork can be electrically conductive. The readings obtained using these meters cannot be relied upon on their own to diagnose rising and penetrating damp. Conductivity meters are a useful tool helpful in producing potential moisture profiles in order to measure possible underlying damp when used correctly.
Conductivity meter readings taken from plaster and masonry of up to around 18% would generally be considered as dry and within acceptable levels in a property of this type provided there is no impact or consequence as a result of the presence of moisture.
Moisture sensitive materials will hold more free water than hard dense materials such as concrete and cement-based products, natural stone, clay brick and lime / ashlar based mortar as used in the construction of this property can absorb a great deal of moisture over time and therefore I would expect higher readings in materials of this type, particularly from external walls which have been exposed to weathering.
The relative moisture contents of skirting boards and lower door frames should be below 22% as this is the level at which decay can occur, ideally relative moisture content of timber work should be between 12-14%.

Skirting in our problem area (front downstairs hall party wall) was at 25%.


We did however have evidence of rotten woodwork under the floor, damp soil under the floor, very high humidity and damp smell. Green mould grew on clothes and woodwork due to the humdity. All due to penetrating damp from next door and blocked sub-floor ventilation (airbricks) due to a conservatory at the back and block paving at the front.


It sounds like you have none of the symptoms and your 'damp meter' readings are pretty good...

DRP

I would be careful at who you allow into your house.

If by 'damp specialist' they mean a damp proofing company then they *will* find damp ...

TheCyclingProgrammer

Yes, insist the damp specialist is independent and not from a damp proofing company. They will have to pay for it.