Failure diagnostics
Why did it go wrong
Every calculator on this site answers “how much”. These pages answer the question that comes after the work, when something has failed.
Each page takes one symptom as somebody would actually describe it and sets out the candidate causes in the order they most often turn out to be the answer — each with the observation that separates it from the others, because a list of possibilities without a way to tell them apart is not much use. Then what to check and in what order, the calculations that relate, and plainly where to stop.
None of it is a diagnosis. Nobody here has seen your building, and a page that spoke with confidence about it would be guessing in a way that sounds like knowledge.
- 60Symptoms
- 360Candidate causes
One from each shelf
60 symptoms
Finishes
Paint, plaster, screed and tiling. Most of these are a bond or a moisture problem, and the failure surface usually says which.
- The paint is peeling off my new plaster5 candidate causes · 5 checks
- My tiles are coming loose or sounding hollow6 candidate causes · 5 checks
- My screed has cracked7 candidate causes · 5 checks
- The edges of my concrete slab have lifted or curled6 candidate causes · 5 checks
- My deck boards have cupped or curled6 candidate causes · 5 checks
- My grout is cracking, powdering or falling out6 candidate causes · 5 checks
- A door sticks, binds or will not close properly6 candidate causes · 5 checks
- My paint is blistering or bubbling6 candidate causes · 5 checks
- My floor squeaks when I walk on it6 candidate causes · 5 checks
- Small round bumps or cracks are appearing over my screws and nails6 candidate causes · 5 checks
- A white powder or bloom keeps appearing on my concrete floor6 candidate causes · 5 checks
- My laminate or engineered floor is lifting, peaking or gapping6 candidate causes · 5 checks
- The joints in my skirting, architrave or coving have opened up6 candidate causes · 5 checks
- My plaster sounds hollow, or has blown off the wall6 candidate causes · 5 checks
- The silicone around my bath or shower keeps failing6 candidate causes · 5 checks
- The paint on my windows or exterior woodwork keeps failing6 candidate causes · 5 checks
- The tiles on my floor are cracking6 candidate causes · 5 checks
- My concrete floor keeps producing dust6 candidate causes · 5 checks
- My worktop is swelling or lifting at a joint6 candidate causes · 5 checks
- My decking is slippery, soft or coming apart6 candidate causes · 5 checks
Services
Electrics and drainage. These are the symptoms where the first useful question is which device or which fixture, because that identifies what was detected.
- A breaker keeps tripping6 candidate causes · 5 checks
- A drain or toilet gurgles when something else is used6 candidate causes · 5 checks
- A radiator is cold at the top, cold at the bottom, or cold all over6 candidate causes · 5 checks
- My boiler pressure keeps dropping and I have to top it up6 candidate causes · 5 checks
- The water pressure is low6 candidate causes · 5 checks
- My pipes bang or knock6 candidate causes · 5 checks
- My toilet keeps running or trickling6 candidate causes · 5 checks
- Smoke comes back into the room from my fire or stove6 candidate causes · 5 checks
- There is a smell of drains in the house6 candidate causes · 5 checks
- My tap drips or leaks6 candidate causes · 5 checks
- My shower runs cold, or keeps changing temperature6 candidate causes · 5 checks
- My boiler is banging, rumbling or whining6 candidate causes · 5 checks
- My cold water pipes are wet, or dripping6 candidate causes · 5 checks
- My toilet flushes weakly, or needs two goes6 candidate causes · 5 checks
- Water is running from an overflow pipe outside my house6 candidate causes · 5 checks
- My lights flicker or dim6 candidate causes · 5 checks
- I have no water, or a pipe has frozen6 candidate causes · 5 checks
- My sink or basin is draining slowly6 candidate causes · 5 checks
- My underfloor heating has cold patches, or never feels warm6 candidate causes · 5 checks
Damp and the building envelope
Where water and cold surfaces meet. Three unrelated problems look alike on a wall, and the remedy for one does nothing for the other two.
- There is a damp patch or mould on an inside wall6 candidate causes · 5 checks
- My gutter overflows when it rains hard6 candidate causes · 5 checks
- There is a water stain on my ceiling6 candidate causes · 5 checks
- There is condensation on my windows6 candidate causes · 5 checks
- There is a white powdery deposit on my brickwork6 candidate causes · 5 checks
- Mould keeps coming back in my bathroom6 candidate causes · 5 checks
- My render is cracking or sounds hollow6 candidate causes · 5 checks
- There is a crack running from the corner of my window or door6 candidate causes · 5 checks
- My loft is damp, or the roof timbers are wet6 candidate causes · 5 checks
- My double glazing has misted up6 candidate causes · 5 checks
- The mortar is crumbling out of my brickwork6 candidate causes · 5 checks
- Tiles or slates have slipped on my roof6 candidate causes · 5 checks
- My ceiling is sagging or bulging6 candidate causes · 5 checks
- My floor bounces or feels springy6 candidate causes · 5 checks
- There is a draught coming from my window6 candidate causes · 5 checks
- My garden or retaining wall is leaning6 candidate causes · 5 checks
- My paving or driveway has sunk in places6 candidate causes · 5 checks
- My fence posts are rotting or the fence is leaning6 candidate causes · 5 checks
- My roof is covered in moss or looks stained6 candidate causes · 5 checks
- The brickwork above my window is cracking or lifting6 candidate causes · 5 checks
- My conservatory is too hot in summer and too cold in winter6 candidate causes · 5 checks
Why these pages do not tell you what is wrong
Because they cannot, and the ones that claim otherwise are the reason this section is written the way it is. A symptom that looks identical in two buildings can have unrelated causes, and the information that separates them — where exactly it is, when it started, what the weather was doing, what is behind the surface — is with the reader rather than with us. So every cause here carries the observation that distinguishes it, and the useful work is done by whoever is standing in front of the wall.
The other half is knowing where to stop. Every page ends with what takes it out of a reader’s hands, and the structural symptoms get no causes list at all. That is not caution for its own sake: an incorrect diagnosis of a structural problem is expensive when it leads to unnecessary work and dangerous when it leads to none.
Where a cause comes down to a quantity — a thickness, a mix ratio, a bay size, a circuit load — the page links the calculator that computes it, with its formula and the standard behind it. That is the loop this site can close and most cannot: the calculation that would have prevented the failure is one click from the failure.