1. Rising
    2. Penetrating
    3. Condensation
    4. Black mould
    5. White salts
    6. Tannin stains
    7. Gas appliances
    8. Design alteration
    9. Hidden histories
    10. Source to symptom




Leaking supply pipes, blocked or broken drains are simple to diagnose. However, moisture rising up a wall defies gravity and has been shown more likely to be moisture drop out caused at the cold base where the wall meets the high mass of the ground. Is it cold, is there a suitable skirting or plinth?




Perpetual drenching from the simulated driving rain of controlled synthetic testing allows for the prediction of failure when applied to modern building materials and junctures.

The traditional hygrothermal envelope performs well at defusing moisture. No cost diagnoses can determine whether internal weather should be considered.




Did it fall out of the sky or drop out of the air? When water is running down the walls a roof leak seems so plausible, remediation begins without properly investigating and diagnosing the problem. The symptom is tackled, but not the cause.

It’s easy to diagnose broken drains, blocked gutters, leaky lead pipes, penetrating and rising damp, but more often than not the problem is condensation. Condensation can literally run down the walls when it’s raining or before, looking like a roof leak or the result of a broken gutter. But what is the real source of the symptom?



Black mould

Black mould – is where pure clean distilled water (condensation) is condensing on the surface which would imply that there is a vapour impermeable layer which could be a layer of vinyl paint; PVA; or damp stopper all of which can be concealed by matt paint or paper not visible on the surface.



White salts

White salts – is effervescent salts, moisture is condensing in the wall (interstitial) and evaporates back through the fabric it deposits the salts as it leaves the surface (as moisture vapour)



Tannin stains

Tannin stains – are where moisture has arrived from the substrate to the surface as a liquid, not vapour, and has carried the tannin that is naturally occurring in the masonry. It can be caused by water penetration but it can also be caused by condensation.



Gas appliances

The combustion of natural gas produces water.

  • 1m3, of natural gas (100,000 BTU, 3 kWh) can produce 2 litres of water.
  • 1m3, of natural gas (100,000 BTU, 3 kWh) can produce 1.5 litres of water.

First answer has mislaid reference, second answer from here


scroll down through the thread, author stands corrected.
100,000 BTU = 1m3 gas
water = 3.25 pounds 1.474175kg

Clarification required




Design alterations

Alterations, extensions, conversions and going open plan. Mitigating modern building layouts and designs.

Downstairs emancipation, an open plan kitchen has increased moisture. Upstair modernity, double glazing and loft insulation have made the walls relatively colder. Moisture is no longer dissipated, it’s condensed on the walls.



Hidden histories

Remediation and decoration. Retail therapy, denial and failure demand.

Removing vinyl paint and cement render exposes an uneven surface that needs putting straight on a budget.



Source to symptom

Vapour is invisible and adds buoyancy to air, creating convection currents.