The Bau-Turbo creates new room to manoeuvre: what the change in the law means for Berlin owners

The key points at a glance

The so-called Bau-Turbo law (construction turbo) came into force on 30 October 2025. For the Berlin real estate market, it means two things. On the one hand, protection of rental apartments against conversion into condominiums was extended by another five years. On the other hand, lawmakers added a clarification that is especially relevant for attic conversions.

Conversion protection remains in place, but with an exception

Since 2021, a city-wide rule has applied in Berlin: anyone who wants to convert rental apartments in buildings with more than five units into condominiums needs a permit. This rule was introduced by the Building Land Mobilisation Act (Baulandmobilisierungsgesetz) and was originally due to expire at the end of 2025. The federal government of CDU, CSU and SPD has extended it until the end of 2030.

The decisive change: the permit requirement will explicitly no longer apply to areas where additional living space is created.

What does "additional living space" mean in concrete terms?

The new wording of the law stipulates that a conversion permit is not required if construction measures create new living area. This refers to:

Roof additions

When an existing building is raised by one or more storeys and new apartments are created there, those apartments are not subject to the permit requirement. The newly created units can be designed and sold as condominiums.

Attic conversions

Until now, some borough offices refused to subdivide newly converted attic apartments, citing conversion protection. This practice is no longer permitted under the new rule. Anyone converting a previously unused attic into living space can subdivide it under the Condominium Act (Wohnungseigentumsgesetz) without a permit.

Extensions and additions

Subsequent additions that create extra living space also fall under the exemption. This applies, for example, to side extensions or to converting space previously used for commercial or other purposes into living space.

The logic behind the rule

The protective purpose of the conversion ban is to preserve existing rental housing. Where investment creates new living space that did not exist before, this protective purpose does not apply. Roof additions and attic conversions enlarge the supply of apartments without sealing new land.

In Berlin, attics are often used only for storage or are not converted at all. At the same time, the options for new development on greenfield sites are limited.

Practical effects for owners

For owners of apartment buildings in Berlin, the change in the law creates legal certainty. Anyone investing in an attic conversion can plan the later sale as condominiums.

A worked example: for an apartment building in Charlottenburg with eight existing apartments and a convertible attic, the average transaction price for condominiums is around 5,720 euros per square metre. For high-quality period buildings with good fittings, prices can be considerably higher. Current valuations show figures of up to 7,900 euros per square metre for modernised period apartments in sought-after locations.

An attic conversion effectively creates new-development living space with modern building standards. Attic apartments are particularly sought after because of their location, often generous ceiling heights and attractive views. In Charlottenburg locations, high-quality converted attic apartments regularly achieve sale prices of 10,000 to 12,000 euros per square metre.

For an attic conversion into two maisonette apartments of around 100 square metres each, you should reckon with construction costs of about 3,500 to 4,500 euros per square metre. For both apartments together, that amounts to an investment of 700,000 to 900,000 euros. At a sale price of 11,000 euros per square metre, the two apartments could be sold for a combined 2.2 million euros.

What does not change?

For existing apartments in buildings with more than five units, the permit requirement remains in place. Anyone who buys a tenanted apartment building and wants to convert the existing apartments into condominiums still needs a permit, which is usually granted only under very strict conditions.

The building-law requirements for attic conversions or roof additions do not change. As before, the relevant development plans, fire safety regulations, structural requirements and neighbours' interests must be observed. The change in the law concerns only the condominium-law question of subdivision.

Outlook: densification in Berlin

Whether the change in the law leads to a rise in attic conversions depends on further factors. Construction costs are still high, tradesperson capacity is scarce and financing is expensive. In addition, many attics are technically difficult to convert or are protected by heritage conservation rules.

The legal clarification removes a major uncertainty. According to expert estimates, attic conversions and roof additions could create tens of thousands of additional apartments in Berlin.

Recommendation for owners

If you own an apartment building in Berlin and are considering an attic conversion or roof addition, you should have the technical feasibility checked by architects and structural engineers, obtain a profitability calculation and clarify the building-law situation. The condominium-law side has been simplified by the new legislation.

For potential buyers of apartment buildings, conversion potential becomes an additional valuation criterion. A building with a convertible attic has gained appeal under the new legal situation.

Conclusion

Lawmakers have extended the protection of existing rental housing and at the same time made it easier to invest in creating new housing through densification. The legal conditions for attic conversions and roof additions are in place. Practice will show whether the rule leads to a rise in such building projects.