Every patch of mould.
Dated as evidence.

Why you should document mould yourself

Mould spreads on the wall, you air the room every day, and still the landlord says: "Your fault, you didn't ventilate." Without dated photos and readings it is only your word against theirs — and the rent reduction falls through. That is exactly what SchimmelLog is for: your documentation that records the condition while you can still see it.

You log every patch with a photo and its spot in the flat, each entry with an automatic timestamp. You also record humidity and dew point per room. That builds a trend over weeks showing how the mould develops despite airing — which is exactly what convinces on a rent reduction.

All entries stay only on your device. No account, no server, no cloud, no sharing. SchimmelLog documents the condition with proof and turns it into a PDF report for your landlord, tenants' association or solicitor on request; the app is not a substitute for legal advice.

Documenting mould: what belongs in every entry

A photo on its own is not yet proof — only a record you can follow makes mould a solid basis for a claim. For your documentation to hold up in front of a landlord, a tenants' association or a court, every entry should capture at least the following:

• Date of discovery — the starting point for working out any deadline
• Room and exact spot — the window reveal, a corner of the room or behind furniture
• Extent of the affected area, ideally with a rough size
• Photo with a date, ideally with an everyday object as a scale
• Likely cause — a leaky window, water damage, condensation or an unclear source
• Notice to the landlord — whether and when you reported the defect
• Accompanying signs — a musty smell, damp marks or affected furniture and clothes

Photos scattered across your phone are almost impossible to place later on. SchimmelLog walks you through the same fields on every entry and files the images, date and location automatically — so a dated timeline builds up that shows since when and to what extent the mould has been there. It is precisely this connection over time that a loose pile of photos can never give you.

Rent reduction for mould: what matters legally

Mould in a rented flat is, as a rule, a defect of the let property. Under § 536 BGB the rent may be reduced for the period the defect exists. The order matters: you must first report the mould to the landlord (§ 536c BGB) and give them a chance to put it right — whoever keeps the defect quiet risks disadvantages of their own.

If the landlord stays inactive, damages or reimbursement of expenses under § 536a BGB may come into play. This is exactly where a complete, dated photo timeline is your strongest argument: it proves onset, spread and duration — and turns a disputed impression into a record you can follow.

Whether a reduction is justified, and by how much, depends on the individual case — on the extent, the cause and the question of who is responsible for the mould (wrong ventilation versus a structural defect, for example). Analysing the cause and assessing it legally is a job for a surveyor, a tenants' association or a lawyer; for health complaints, seeing a doctor is important. SchimmelLog gives you the ordered evidence — not legal or medical advice.

How to document mould properly

Good photo evidence is built early and regularly, not once the dispute is already on. Here is how to go about it:

• Start early: photograph the first spot instead of waiting until it has spread.
• Re-photograph regularly: fresh shots at intervals show the spread over time.
• Use a scale and context: a folding ruler or a familiar object makes the size easy to judge.
• Note the cause: moisture, condensation or a structural defect — record what you observe.
• Report the defect in writing: document when and how you told the landlord.

That way, if it comes to it, you have no vague recollection but a dated chronicle — from the first spot to its removal. That is the basis a tenants' association or a lawyer needs before they can even assess your claims. And even if it never comes to a dispute, a clear timeline helps you move the landlord to act on the facts and the evidence, instead of leaving things at vague complaints.

More help for tenants

Mould is only one of many tenancy issues. Whether you need to log neighbour noise, secure your deposit with a handover report or check an owner-occupancy eviction notice, the principle is the same: only complete, timely documentation protects your rights as a tenant in the end.