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ReiVi · One app, one job

SchimmelLogfor tenants

The landlord says "you did not air the apartment properly," and the rent reduction is off the table.

Document mold, with date, photo and humidity

Record every patch of mold with a photo and its location in the apartment, and the app sets the date and time. You also enter humidity and temperature for each room. Over weeks this builds a record that you give as a PDF to your landlord, a tenants' association or a lawyer.

View on Google Play

For Android · free with ads · PDF report as a one-time purchase

  • No account
  • Entries stay on your device
  • Logging works offline
  • No subscription
Page 1
Mold record · Sample with made-up entriesNov 1 to Nov 30
DateRoomFindingHumidity
Mon, Nov 2Bedroomleft window reveal, about 20 × 30 cm68%
Thu, Nov 12Bedroompatch larger, about 25 × 35 cm66%
Sat, Nov 21Bathroomnew patch in the ceiling corner71%
Mon, Nov 30Bedroomabout 30 × 45 cm, despite daily airing64%
Entries in this period4, landlord informed on Nov 5

All entries are made up and only show what a log looks like.

How your mold record comes together

  1. Photograph the patch

    Create an entry for the room and photograph the mold. The app sets the date and time.

  2. Enter the readings

    Humidity and temperature have their own fields. That way you see for each room how the readings develop.

  3. Record as a PDF

    All entries are listed in chronological order. The PDF report contains photos, readings and dates, and you send it on by email.

What belongs in a mold record

A photo on its own only shows one moment. Only several dated entries show since when and to what extent the mold has been there. For each entry, include:

DetailExampleIn the app
Date it was foundNov 2automatic
Room and spotbedroom, left window revealroom per entry
Photopatch with a folding ruler next to itphoto with date
Humidity and temperature68%, 18 degreesown fields
Extentabout 20 by 30 cmno separate field
Report to the landlordby letter on Nov 5no separate field

You can also write this down on paper. How to decide is covered further down under "Paper or app?"

Rent reduction because of mold: the order matters

Mold in an apartment is, as a rule, a defect in the rented property. In Germany, under § 536 of the Civil Code (BGB), the rent can be reduced for the period in which the defect exists.

First you have to report the mold to the landlord (§ 536c BGB) and give them the opportunity to remove it. If they do nothing, damages or reimbursement of expenses under § 536a BGB may be added in some circumstances.

Whether a reduction is justified, and by how much, depends on the individual case: on the extent, on the cause and on who is responsible for the mold. Whether incorrect airing or a structural defect is behind it is for experts to clarify. The legal assessment is done by a tenants' association or a lawyer, and if you have health problems, medical advice is important.

How to document mold

  • Start with the first patch, not only once it has spread.
  • Take follow-up photos at intervals so the spread becomes visible.
  • Place a folding ruler or a familiar object next to it.
  • Note what you observe about the cause: condensation, a leaky window, water damage.
  • Report the defect in writing and record when you informed the landlord.

Paper or app?

Photos in your gallery and a note with readings cost nothing. But after a few weeks you often no longer know which picture belongs to which room and which day.

The app links photo, date, room and readings to each entry. At the end you get the record as one PDF.

MerkmalPaper templateApp
Costnonefree with ads, PDF as a one-time purchase
Photosseparately in the galleryon the entry, with date
Recordgather it togetherchronological per room
Sharingcopy or scan itshare the PDF

What the app costs

no subscriptionbuy once

Recording is completely free and without limits. The free version shows ads. A one-time purchase in the Play Store unlocks the PDF report and removes the ads. There is no subscription.

Common questions about mold in a rented apartment

Do I need my own record?

Dated photos and humidity readings are your basis when dealing with the landlord. They show since when the mold has been there and what the rooms looked like.

Do I have to report the mold to the landlord?

Yes, in Germany you have to report a defect under § 536c BGB. Record when and how you did this, for example by a dated letter.

Does the record help with a rent reduction?

The dated record shows how the mold develops despite airing. Whether a reduction holds up and how much it can be depends on the individual case.

Does the app replace a building inspector?

No. The app records what you see and measure. In a dispute, an expert clarifies the cause.

Can I share the report as a PDF?

Yes. The PDF report (one-time purchase) contains all photos, humidity readings and dates. You send it by email to your landlord, a tenants' association or a lawyer.

Does the app work without internet?

Yes, recording works offline. Your entries stay on your device, and you do not need an account.

This app is made by ReiVi, the app label of Viktor Reinik from Freilassing, Germany. Every ReiVi app does exactly one job and works without an account. Who is behind ReiVi (in German)

View on Google Play

Legal basis (Germany): § 536 BGB (rent reduction), § 536a BGB (damages), § 536c BGB (reporting the defect). This page is not legal or medical advice. For health problems, ask a doctor; for legal questions, ask a tenants' association or a lawyer. Updated on October 26, 2026.

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