Modernisierung: tenant rights & rent increase (2026)

What does a Modernisierung mean for you as a tenant?

A Modernisierung (modernisation) is building work that permanently improves your flat – for example an energy-efficiency upgrade, a new bathroom, or installing a lift. Unlike pure Instandhaltung (maintenance, keeping the existing condition), the landlord may pass part of the cost of a genuine Modernisierung on to the rent.

The most important point first, in one sentence: your landlord must announce the work at least three months in advance (§ 555c BGB), you must generally tolerate it (§ 555d BGB), and afterwards may add 8 % of the costs per year to the rent (§ 559 BGB) – but capped at 3 €/m² over six years (§ 559 Abs. 3a BGB). Against both the work and the increase, you have clearly defined rights.

How much can the rent rise? The 8 % rule and the Kappungsgrenze (§ 559 BGB)

Once the Modernisierung is complete, the landlord may raise the annual rent by 8 % of the costs attributable to your flat (Modernisierungsumlage, modernisation surcharge, § 559 Abs. 1 BGB). This increase is permanent and follows its own logic – it is independent of the ortsübliche Vergleichsmiete (local reference rent) and the Kappungsgrenze (cap on rent increases) of § 558 BGB.

What matters for you: before the 8 % is calculated, two items must be deducted.

• Saved maintenance costs (ersparte Instandhaltungskosten, § 559 Abs. 2 BGB): if the work replaces a repair that was due anyway (e.g. old, broken windows for new ones), the repair share may not be passed on.
• Public subsidies and low-interest loans (Fördermittel, § 559a BGB): if the landlord received grants or subsidised credit, these reduce the costs that can be passed on.

And above all sits the Kappungsgrenze (§ 559 Abs. 3a BGB):

Your rent before the increase	Maximum increase over 6 years
7 €/m² or more	3 €/m²
below 7 €/m²	2 €/m²

The cap applies per square metre of living space over six years. Even if the 8 % formula yields more, your rent may not rise by more than this.

A worked example

How to check the increase step by step:

1. Modernisation costs for the flat: 12,000 €
2. Deduct saved maintenance (§ 559 Abs. 2 BGB): − 2,000 €
3. Deduct subsidies (§ 559a BGB): − 0 € (none here)
4. Costs that can be passed on: 10,000 €
5. 8 % per year (§ 559 Abs. 1 BGB): 800 €/year → 66.67 €/month

Cap check for a 60 m² flat with a starting rent above 7 €/m²: the maximum is 3 €/m² × 60 m² = 180 € over six years. The calculated 66.67 €/month is below that, so the increase is allowed. If the starting rent were below 7 €/m², the limit would be 2 €/m² × 60 m² = 120 €, and the increase would be reduced.

Achtung: Always check that the saved maintenance was deducted – this is the most common error at your expense. And watch the deadline for the Härteeinwand: notify the landlord in writing by the end of the month following receipt of the announcement (§ 555d Abs. 3 BGB), or the right may lapse.

Do I have to tolerate the Modernisierung? (§ 555d BGB)

In principle yes: for a properly announced Modernisierung there is a Duldungspflicht (obligation to tolerate, § 555d Abs. 1 BGB). You must allow the work in your flat.

But: you may refuse if the work – or the later rent increase – would cause a hardship for you, your family or other household members that cannot be justified even when the landlord's interests are weighed in (Härteeinwand, § 555d Abs. 2 BGB). The grounds can be structural, health-related, personal or financial.

The deadline matters: you must raise the Härteeinwand in writing by the end of the month following receipt of the announcement (§ 555d Abs. 3 BGB). If you miss it through no fault of your own, you can only bring hardship grounds later in exceptional cases, and only if you do so promptly.

When must I pay the higher rent?

After the work is finished, the landlord declares the increase in writing (Erhöhungs­erklärung, increase notice, § 559b BGB). The higher rent is only payable from the start of the third month after receipt of the notice (§ 559b Abs. 2 BGB). If the announcement was faulty, or the announced costs were exceeded by more than 10 %, the payment start shifts by a further three months.

Can I move out? Your Sonderkündigungsrecht (§ 561 BGB)

Yes. As soon as the landlord asserts a Modernisierungsmieterhöhung under § 559 BGB, you have a Sonderkündigungsrecht (§ 561 BGB). You can give extraordinary notice up to the end of the second month after receipt of the increase notice; the tenancy then ends at the close of the month after next. In that case you do not have to pay the higher rent.

Common mistakes

• The saved maintenance is not taken out of the costs – the increase then comes out too high (§ 559 Abs. 2 BGB).
• The Härteeinwand is raised too late and lapses (§ 555d Abs. 3 BGB).
• The higher rent is paid immediately, although it is only due from the third month (§ 559b Abs. 2 BGB).
• The Modernisierungsankündigung is incomplete (e.g. the expected rent increase is missing) – in which case the toleration deadline never starts (§ 555c BGB).

Mit HausMaus geht das einfacher

For tenants, HausMaus is free. If you receive a Modernisierungsmieterhöhung, HausMaus checks the increase against the limits of § 559 BGB – the 8 % on the costs that can be passed on, and the cap of 3 €/m² (or 2 €/m²) – and you can consent or object (Widerspruch) straight from the app. The deadline tracker keeps an eye on the dates for your Härteeinwand and your Sonderkündigungsrecht, and the Mietrechts-Assistent answers your questions about the work – all in one place. That way you can see calmly what is lawful before you respond.

See pricing – 1 % of collected rent, free for tenants →