It exists, but it is diagnosed far more often than it occurs. Most low-level damp turns out to be penetrating moisture, a bridged damp-proof course, high external ground levels or condensation — all of which have different and usually cheaper remedies.

Should I get the free survey a damp company offers?

You can, but read it for what it is. A free inspection from a firm that sells injection and tanking has an obvious commercial direction. An independent report costs money and is not tied to a product.

The mould keeps coming back after I clean it. Why?

Cleaning removes the growth, not the conditions. Mould returns where surfaces stay cold and humid, so the fix is usually a combination of ventilation, heating pattern and insulation rather than a stronger cleaning product.

Damp survey (independent moisture diagnosis)

Damp survey

Independent diagnosis of penetrating damp, condensation and rising damp — including why meter readings alone should never justify a chemical injection quote.

Ask KJ about a damp problem 01706 318200

Last reviewed 31 August 2026

What does a damp survey involve?

A damp survey identifies why a building is wet. The surveyor examines the affected areas and the parts of the building that feed them — ground levels, rainwater goods, roof detailing, ventilation, heating patterns and construction type — then reaches a diagnosis. Moisture meters support the assessment; they do not make it. The output is a cause, the evidence for it and a remedy proportionate to that cause.

At a glance

Three broad causes: Penetrating damp, condensation, and true rising damp — commonly confused.
Independence: The report does not sell the remedial work it recommends.
Instruments: Meters indicate. Diagnosis comes from construction, pattern and context.
Frequent finding: Condensation and a maintenance failure, not a failed damp-proof course.

The three causes behave differently

Penetrating damp arrives from outside through a specific defect: a blocked gutter, a cracked render panel, a failed flashing, a bridged cavity, or ground raised above the damp-proof course. It is usually localised, follows the weather and worsens after rain.

Condensation is generated inside. It concentrates on cold surfaces, in corners, behind furniture on external walls and around thermal bridges, and it is a balance of moisture production, ventilation and heating. Mould growth is its signature rather than salt staining.

True rising damp is the least common of the three and the most frequently diagnosed. It shows as a broadly horizontal tidemark low on a wall, with hygroscopic salts drawn in with the moisture. Damage to a damp-proof course, or a bridge across it, has to be demonstrated rather than assumed.

Why meter readings are not a diagnosis

The handheld meters used in most damp inspections measure electrical resistance or capacitance. They respond to salts, foil-backed plasterboard, metal fixings and dense masonry as readily as to water, which is why a high reading on a plaster surface proves very little on its own.

A defensible report says where the moisture is, what pattern it forms, what construction lies behind it and what external or internal conditions explain that pattern. A row of meter readings with a chemical injection quote attached is a sales document, not a diagnosis.

External ground levels, paving and abutting structures
Rainwater goods, roof detailing and render or pointing condition
Construction type: solid wall, cavity, traditional lime, modern cement
Heating pattern, extraction, trickle ventilation and occupancy

Traditional buildings need different thinking

Solid-walled and traditionally built properties manage moisture by allowing it to move through and evaporate. Cement renders, plastic paints and impermeable internal finishes interrupt that, and the resulting trapped moisture is regularly mistaken for rising damp.

In those buildings the remedy is often to remove the impermeable layer rather than add another one. Getting this wrong is expensive and can accelerate decay in embedded timbers.

Who this is for

A good fit if

Owners who have had a damp-proofing quotation and want an independent view
Buyers whose survey has recommended a further damp investigation
Landlords addressing a mould or condensation complaint properly
Owners of solid-wall or period properties with recurring damp

Not the right choice if

Anyone wanting a free inspection from a company that also sells the treatment
Structural assessment of walls affected by movement rather than moisture
Testing or removing suspected asbestos-containing materials

Before you accept a damp-proofing quote

The order in which you take advice determines whether you fix the cause or redecorate over it.

1.Get the diagnosis from someone who is not selling the cure
Independence is the whole value of the exercise.
2.Exhaust maintenance and ventilation first
Clearing gutters, lowering ground levels and improving extraction resolves a substantial share of reported damp.
3.Check whether decay has followed the moisture
Persistent wetness in contact with structural timber is the point at which the problem stops being cosmetic.
Timber surveys
4.Then specify remedial work to the diagnosed cause
Contractors quote reliably when they are pricing a defined defect rather than a symptom.
Defect surveys

When to bring in a specialist

Remedial damp-proofing, tanking and re-plastering: a specialist contractor working to the diagnosed cause.
Structural calculations, load paths and remedial design: a structural engineer. A surveyor describes and diagnoses; it does not design.
Suspected asbestos-containing materials: a competent asbestos surveyor, with analysis by an accredited laboratory.
Liability between neighbours, lease repair obligations and seller disclosure: your solicitor or conveyancer.

Common questions

Limitations and sources

The inspection is visual and non-intrusive. Plaster is not hacked off and floors are not lifted unless separately agreed.
Moisture readings taken on one day reflect the conditions of that day; seasonal and weather-driven damp may need a repeat visit.
Where the moisture source lies in a neighbouring property, access limits what can be established.
Nothing on this page is a professional opinion about a specific property. KJ Surveyors has not inspected your building, and general guidance cannot replace an inspection and report.

Source: RICS · checked August 2026

Source: Historic England · checked August 2026

Source: UK Government · checked August 2026

Last reviewed 31 August 2026.

Where to go next

timber decay investigation — where prolonged damp has reached structural timber.
thermal imaging — to locate cold spots and moisture patterns behind finishes.
a specific defect survey — when one problem needs a focused report rather than a whole-property survey.

Damp you cannot explain?

Tell KJ where the damp appears, the age and construction of the property, and what you have been quoted. KJ will explain what an independent diagnosis should establish.

KJonline

Free surveying guidance across North West England

Hi, I'm KJ. Tell me about the property or the surveying advice you need and I'll help you work out the right next step.

KJ gives general guidance only and has not inspected your property. A professional opinion follows an inspection by a surveyor.