Renovating an underground car park in a WEG: damage, process and who pays

Why the underground car park ages so expensively

Every car that drives in during winter brings road salt with it. The meltwater drips onto the floor slab, evaporates and leaves chlorides behind, a little more every year. At some point they reach the reinforcement. From then on the steel rusts, the rust takes up more space than the iron, and the concrete spalls from the inside.

The treacherous part is the order of events: the damage forms years before anyone sees it. By the time the first rust streaks appear on the columns, the reinforcement is often already affected over large areas. The driving lanes, the ramp, the base of the columns and every spot where water stands are particularly at risk.

If there is a courtyard, garden or playground on top of the car park, a second risk comes in: the waterproofing of the deck. It cannot be repaired from below. If it leaks, everything above has to come off — planting, paving, play equipment. That is usually the most expensive part of renovating an underground car park.

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How to tell that renovation is due

At the next inspection, look at these spots:

• Rust streaks or spalling on columns, walls and the underside of decks
• White deposits (efflorescence) along cracks — water is moving through the concrete here
• Damp or dark patches on the ceiling, especially under courtyards and green areas
• Puddles that no longer dry out, and blocked drainage channels
• Worn, cracked or blistered coating in the driving lanes and on the ramp
• Exposed reinforcement — at that point it is no longer a question of planning but of safety

Each of these findings is a reason to bring in a specialist. None of them is a reason to ask straight away for a coating quote.

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Who owns what

Since the WEG reform, parking spaces can be separately owned in their own right; the law treats them like rooms (§ 3(1) sentence 2 WEG). That changes nothing about the structure: parts required for the building's stability and safety are always common property (§ 5(2) WEG).

For the car park, that usually means:

Common property	Separate ownership (if set up that way)
Floor slab, decks, columns, walls	the individual parking space as an area
Waterproofing and surface protection
Ramp, driving lanes, drainage
Ventilation, gate, lighting, fire protection

How it is set up in your complex is stated in the declaration of division (Teilungserklärung). Some associations hold the car park as one unit with many co-owners; others run it as a sub-association with its own cost allocation.

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Who pays

The default. The costs of maintaining common property are borne by all owners by co-ownership share (§ 16(2) sentence 1 WEG) — including those who have no parking space at all. That surprises many people, but it is the statutory rule.

The community rules. Many declarations of division assign the car park's costs to the parking space owners or set up a sub-association. Where the community rules validly provide for this, the parking space owners can also resolve on a special levy for the car park on their own (Federal Court of Justice, BGH, judgment of 12 November 2021 – V ZR 204/20).

A resolution. Since 2020, the association can resolve by simple majority on a different allocation for individual costs or particular types of costs (§ 16(2) sentence 2 WEG). The BGH has since confirmed this in both directions:

• The association may place the costs of a measure solely on those who benefit from it (judgment of 22 March 2024 – V ZR 81/23).
• It may equally lift an agreed separation between building and car park and spread the renovation costs across everyone (judgment of 14 February 2025 – V ZR 236/23).

Either way, the resolution must amount to proper management: it needs an objective reason and must not burden individual owners arbitrarily. Because large sums are at stake, this resolution in particular is prone to challenge. Have the cost allocation checked before the meeting and give the reasons in the wording of the resolution.

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How a renovation runs

1. Survey by a qualified planner. Concrete repair is not a painting job. Where structural safety is affected, the technical rules require a qualified planner (sachkundiger Planer); the Bavarian Chamber of Civil Engineers recommends bringing one in at the latest before cracks are closed (guidance note on car parks, in German). The planner measures how deep the chlorides have penetrated, how much concrete cover is left and where the reinforcement is already corroding.

2. Repair concept with options. Good planners show more than one solution: for example, local repair with a coating compared with a crack-bridging system, with costs today and over the service life. For the owners' meeting, that comparison is worth more than any single figure.

3. Resolutions. Usually in two steps: first, appointing the planner for the survey and concept; then the measure itself, with a cost framework, financing and cost allocation.

4. Tender. Using the planner's specification, so that every bidder quotes for the same work. Only then are quotes comparable.

5. Works in sections. The whole car park is almost never closed at once. Plan replacement parking, information for tenants and access for the site early on.

6. Acceptance and care plan. After acceptance, maintenance begins: visual checks of the coating, a thorough wet clean every spring to remove salt residue, care of drainage channels and joints. Surface protection only lasts as long as it is looked after.

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Which surface goes where

Under the technical rules, the systems are called OS 8, OS 11 or OS 14. For the owners' meeting, the basic idea is enough:

• Rigid systems (OS 8) protect floor slabs where no new cracks are expected. They are robust and comparatively inexpensive.
• Crack-bridging systems (OS 11, OS 14) are needed where the structure moves and cracks can open, such as intermediate decks and trafficked decks. They cost considerably more.

Which system fits is decided by the planner after the survey, not by the coating contractor's quote.

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What a renovation costs

To be honest: nobody knows before the survey. Per-square-metre prices found online vary many times over, because the real cost driver sits invisibly beneath the surface — how much concrete has to be removed and how much reinforcement replaced.

What to budget for:

• Planner and survey — a manageable amount that prevents the biggest wrong decisions
• Concrete repair — the variable part, depending on the damage
• Surface protection — depending on the system and the area
• Ancillary costs — replacement parking, site setup, drainage, lighting and markings
• Contingency — with concrete repair, the true extent often only shows once the concrete is opened up

The good news: survey early, and the renovation is usually smaller. The bad news: every year of waiting in a chloride-contaminated car park enlarges the area that eventually needs extensive repair.

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Inspection duties in Bavaria

The Bavarian Garage and Parking Ordinance (GaStellV) distinguishes small, medium-sized and large garages by floor area. For medium-sized and large garages, the Safety Systems Inspection Ordinance (SPrüfV) applies: ventilation and CO warning systems required by building law must be tested by certified inspectors before first use, after significant changes and then again within three years on a recurring basis; defects found must be remedied without delay (§ 2 SPrüfV).

Not every residential garage needs mechanical ventilation. Enclosed single-storey underground garages with little traffic can, under certain conditions, manage with natural ventilation (§ 14 GaStellV). Which systems your garage requires follows from its building permit. It belongs in every property file — and if it is missing, finding it is the first item on the list.

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Plan for charging

A renovation is the cheapest moment for the electrical infrastructure. Every owner can demand reasonable structural changes that serve the charging of electric vehicles (§ 20(2) WEG). Plan conduits and a basic installation while the car park is open, and you save cutting it open a second time later. More in our article on wall boxes and balcony solar in a WEG.

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Large complexes: a car park under several buildings

In residential complexes, the car park often lies beneath several buildings and the courtyard between them. Then more depends on it than the parking spaces: the waterproofing under the courtyard, the drainage of the outdoor areas, sometimes the access to the stairwells. This is where it is decided whether an association can plan a renovation or is caught out by it.

If your complex has one, it belongs in the multi-year maintenance plan — as its own item and, where the community rules provide for it, with its own reserve. How we manage large complexes is set out under property management for residential complexes.

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Ravenica has underground car parks in the associations it manages surveyed before every renovation and tenders using the planner's specification — so the owners vote on the right measure, not on the first quote.