10.06.2026

Hoai Core Services: Fundamentals, Process, and Practice

Building design

Textile material in white, green, and brown—a look at natural materials in outdoor spaces. Photo: plhnk

Anyone who commissions architects, engineers, or landscape architects operates within a fee structure that has formed the basis for the compensation of planning services for decades. The HOAI Basic Services are at the heart of this system: They define which activities are part of the standard scope of a planning contract, how these services are divided into phases, and how the fee is calculated based on them. Anyone who understands this system can read planning contracts, evaluate service specifications, and competently assess fee proposals.

What HOAI Basic Services Are and How They Differ from Special Services
How the scope of services is divided into service phases and what each phase entails
How the fee is calculated based on billable costs, fee zones, and service phase shares
What role the HOAI plays in the planning contract and what has been in effect since the 2021 amendment
How basic services are defined, documented, and billed in practice
What typical errors and misunderstandings arise during application
How the scope of services for building design differs from that of landscape design
The significance of the HOAI for tenders, contract awards, and quality assurance

What HOAI basic services are: definition and systematic classification

The Fee Schedule for Architects and Engineers (HOAI) is a German statutory regulation that governs fees for planning services. It applies to all services provided in Germany, regardless of the planner’s nationality or place of business. Within this regulation, HOAI basic services play a central role: They describe the scope of services considered necessary and customary for the proper fulfillment of a planning contract. Basic services are therefore not the minimum that can be provided, but rather the defined standard scope that ensures the client receives complete and professional planning.

The HOAI distinguishes between two categories of services: basic services and special services. Basic services are exhaustively listed in the scope of services for the respective discipline and form the basis for calculating the fee. Special services go beyond this standard scope, are not included in the fee for basic services, and must be agreed upon and compensated separately. Typical special services include, for example, the development of operational concepts, the conduct of economic feasibility studies, or the design of interior spaces, provided these are not already included in the scope of services. In practice, the distinction is not always clear-cut and regularly leads to discussions between clients and planners.

The HOAI applies to various disciplines, including buildings and interiors, outdoor facilities, civil engineering structures, transportation facilities, structural engineering, technical equipment, as well as urban planning and land-use planning. Each discipline has its own scope of services with its own basic services. For landscape architects, the scope of services for outdoor facilities is particularly relevant; it is regulated separately in the HOAI and differs in key respects from the scope of services for building design. Common to all scopes of services is the division into nine service phases, even though not every discipline encompasses all nine phases.

The Nine Service Phases: Structure, Content, and Weighting

At the heart of the HOAI’s basic services is the division of the planning process into nine sequential service phases, abbreviated as LPH 1 through LPH 9. These phases cover the entire planning and implementation process, from the initial concept to commissioning. Each phase is assigned a percentage of the total fee that reflects the relative importance and effort involved in that phase. These percentages are specified in the HOAI and can only be contractually modified within narrow limits.

Service Phase 1 encompasses the preliminary study. Here, the planner clarifies the project scope, advises the client on fundamental issues, and compiles the planning requirements. This involves assessing the existing conditions, clarifying the objectives, and making an initial feasibility assessment. This phase is often underestimated, but it forms the basis for all subsequent decisions. Service Phase 2 involves preliminary planning, during which potential solutions are developed, alternatives are examined, and a coordinated planning concept is formulated. Initial cost estimates in accordance with DIN 276 are also prepared during this phase, providing the client with an early indication of the financial framework.

Service Phase 3 is the design planning phase. It refines the concept into a detailed design that covers all essential parts of the construction project and enables a cost calculation in accordance with DIN 276. Service Phase 4 comprises the permitting phase, i.e., the preparation of documentation for the building permit process or comparable approval procedures. In Service Phase 5, the construction drawings are prepared: drawings and written descriptions at a level of detail that enables the execution of the construction work. This phase is particularly time-consuming and accounts for a correspondingly high proportion of the fee in the “Building” service package.

Service Phases 6 and 7 concern the preparation for and participation in the contracting process. The planner prepares bills of quantities, evaluates bids, and participates in the awarding of contracts. In Service Phase 8, which involves on-site supervision or project monitoring, the planner monitors the execution of construction work to ensure compliance with the planning documents, coordinates the participating specialist planners, and documents construction progress. In practice, this phase is particularly relevant in terms of liability. Finally, Service Phase 9 encompasses project aftercare: the inspection to identify defects before the statute of limitations expires, as well as the supervision of defect rectification.

Fee Percentages and Their Significance for Contract Drafting

The percentage-based fee allocations for the individual service phases are specified separately in the HOAI for each discipline. In the case of building design, for example, a significant portion is allocated to service phases 3 and 5—that is, conceptual design and construction design—while the early phases 1 and 2 together account for only a small portion of the total fee. This has an important implication for contract drafting: If a client commissions only individual service phases, the designer receives only the corresponding portion of the total fee. If service phases are not commissioned or are terminated after planning has begun, questions arise regarding when fees become due and deductions for saved expenses, which are extensively addressed in case law.

It is not mandatory to commission all service phases. It is contractually possible to agree on only parts of the scope of services—for example, only service phases 1 through 4 for permit planning without construction detailing and construction supervision. In such cases, a clear contractual provision is essential, as otherwise ambiguities regarding the scope of services owed may arise, which can lead to disputes.

Fee Calculation: Chargeable Costs, Fee Zones, and Minimum Rates

The fee for HOAI basic services is not set at a flat rate but is calculated according to a defined system based on three parameters: the billable costs, the fee zone, and the fee rate within the fee schedule. The billable costs are the costs of the construction work used to calculate the fee. They do not necessarily correspond to the total construction costs, but rather to a defined portion thereof, which is specified in the HOAI for each discipline. In building design, these are primarily the costs of cost groups 300 and 400 according to DIN 276, i.e., building structure and technical systems.

The fee zone describes the difficulty and planning effort involved in a project. The HOAI generally distinguishes between five fee zones, with Fee Zone I describing simple requirements and Fee Zone V describing very high requirements. Classification is based on evaluation criteria listed in the HOAI for each discipline. For the scope of services related to outdoor facilities for landscape architects, these include, for example, the number of functional areas, terrain modeling, the design of outdoor elements, and integration into the urban context. The fee zone has a significant impact on the fee: A project in fee zone IV can command a significantly higher fee than a comparable project in fee zone II, even with identical billable costs.

Within each fee zone, the HOAI specifies fee schedules that set minimum and maximum rates for different levels of billable costs. Clients and planners are free to agree on the fee within this range. If no agreement is reached, the minimum rate is deemed to have been agreed upon under current law. The question of whether minimum rates are mandatory or whether rates below them are permitted was long disputed and has been redefined by a 2019 ruling of the European Court of Justice and the subsequent amendment to the HOAI in 2021: Since then, the fee schedules are no longer binding in the sense of mandatory pricing law but serve as a guideline from which contractual deviations are permitted. This change has significant implications for the practice of fee agreements.

Special Features of the Scope of Services for Outdoor Spaces

The scope of services for outdoor facilities—which is central to the work of landscape architects and open-space planners—has several distinctive features compared to the scope of services for buildings. The billable costs here include the construction costs of the outdoor facilities, including planting work, but exclude the costs of works of art and special furnishings, unless these are part of the scope of services. Fee zones I through V are determined based on characteristics such as the diversity of usage requirements, terrain modeling, integration into the existing environment, and the complexity of the planting. A simple parking lot is generally classified in Fee Zone I or II, while a complex city square with water features, planting, and lighting is classified in Fee Zone IV or V.

It is important for landscape architects to know that the HOAI’s basic services for outdoor facilities also include services that are taken for granted in the building sector but are often underestimated in the outdoor space sector: the preparation of construction drawings at a scale of 1:50 or larger, the preparation of specifications for all trades involved in the outdoor facility, and construction supervision, including documentation. Those who do not provide these services in full risk not only fee reductions but also liability risks in the event of defects in the completed facility.

HOAI Basic Services in Planning Practice: Delimitation, Documentation, and Billing

Applying HOAI basic services in daily planning practice requires a careful definition of the scope of services, comprehensive documentation of the services rendered, and accurate fee calculation. Common errors arise as early as the contract drafting stage: If the contract does not clearly define the scope of services, disputes arise as to whether a particular activity is part of the basic services or constitutes a special service that must be compensated separately. Experts recommend drafting the contract based on the HOAI service profile, explicitly specifying which service phases are commissioned and whether individual basic services are excluded or supplemented by special services.

Documenting the services rendered is important not only for billing but also in the event of a liability claim. If a client later claims that the planner failed to perform a specific basic service, the planner must be able to prove that they did perform it. Meeting minutes, plan delivery lists, correspondence, and handover reports are indispensable in this regard. Service Phase 8, construction supervision, requires particularly extensive documentation: construction logs, photographic documentation, and defect reports are part of the basic services owed and, at the same time, serve as important evidence in the event of a dispute.

The final fee invoice upon completion of the services must determine the billable costs based on the actual construction costs, justify the fee bracket, and itemize the service phases performed along with their respective percentages. If the actual construction costs deviate significantly from the originally estimated costs, the fee also changes because the billable costs must be recalculated. Cost increases therefore generally lead to a higher fee, while cost reductions lead to a lower one. This mechanism sometimes comes as a surprise to clients, but it is an essential feature of the HOAI system.

Common Errors and Misunderstandings in Applying the HOAI

One of the most common misunderstandings is viewing the HOAI as a price list from which one can simply select an amount. In fact, determining the fee is a multi-step process that requires precise knowledge of the billable costs, the fee zone, and the commissioned service phases. Anyone who skips these steps and works solely with flat rates risks either charging too little or entering into a contract that does not reflect the actual effort involved.

Another common mistake is confusing basic services with special services. Many clients assume that everything a planner does as part of a project is covered by the base fee. This is incorrect: Special services such as the development of operational concepts, the design of public art installations, or the conduct of public participation processes are not included in the basic fee and must be agreed upon and compensated separately. If this agreement is missing, a dispute arises that often ends up in court.

The issue of the completeness of basic services is also often underestimated. Basic services cannot be arbitrarily divided: If a planner performs only a portion of the basic services for a phase, they are still obligated to provide the entire phase if they have contractually agreed to do so. Conversely, a client who prevents the planner from providing the full scope of services—for example, by prematurely terminating the project or withholding planning documents—cannot simply reduce the fee. Case law has developed an extensive body of precedent on this matter, which both planners and clients should be familiar with.

Finally, the significance of the fee zone for determining the fee amount is often underestimated or deliberately ignored. Some clients tend to classify projects into lower fee zones in order to drive down the fee. Planners who agree to an incorrect classification without carefully reviewing the evaluation criteria forfeit fees and expose themselves to the risk of working for an effort that is not adequately compensated. The fee zone is not a matter for negotiation, but rather an objective classification based on defined criteria.

HOAI Basic Services in the Context of Contracting, Competition, and Quality Assurance

The HOAI basic services serve not only a fee-related function but also a quality-assurance purpose. By defining the minimum scope of proper planning, they establish a standard against which service delivery can be measured. Public-sector clients who put planning services out to bid in accordance with public procurement law use the HOAI scope of services as the basis for the service specifications. The basic services form the core of the scope of services put out to bid, which can be supplemented by special services.

In design competitions conducted in accordance with the Guidelines for Design Competitions (RPW), the HOAI basic services also play a role: The winner of a competition is generally entitled to be commissioned to perform the planning services, with the fee calculated according to the HOAI. The competition entry itself is not part of the HOAI basic services but is compensated through the competition’s prize money. This distinction is important to avoid double compensation while ensuring that the planner is appropriately compensated for their competition work.

For landscape architects and open-space planners, who are frequently involved in public projects, knowledge of the HOAI basic services is a fundamental requirement for professional practice. Those unfamiliar with the scope of services for open spaces can neither negotiate a fair contract nor clearly communicate their scope of work to the client. The HOAI is not a bureaucratic obstacle, but rather a tool that provides certainty to planners and clients alike: to planners through a defined fee structure, and to clients through a clearly described scope of services.

HOAI Basic Services as the Foundation of Professional Planning Work

The HOAI Basic Services are far more than a set of fee regulations. They describe the process that high-quality planning must undergo, from the initial scoping phase to the final project supervision. Those who understand this process and apply it consistently deliver not only a legally sound service but also a technically comprehensive one. The service phases are not a bureaucratic framework but reflect the actual logic of planning and construction: first clarify, then design, then detail, then put out to bid, then supervise, then document.

The 2021 amendment to the HOAI relaxed the binding nature of the fee schedules but did not fundamentally change the scope of services itself. The basic services remain the benchmark for proper planning services, even though fee agreements can now be structured more flexibly. This flexibility is an opportunity for planners who can clearly communicate the scope and quality of their services and be compensated accordingly. However, it also poses a risk for planners who, under competitive pressure, agree to fees that do not cover the actual effort involved.

For everyone working in planning, the following applies: Knowing the HOAI basic services does not mean memorizing a set of rules, but rather understanding one’s own daily professional practice within a structured framework. Those who know what is required in each service phase, can objectively justify their project’s fee zone, and has a firm grasp of the difference between basic services and special services is not only on the safe side when it comes to fee law but is also professionally capable of presenting themselves transparently and convincingly to their clients. That is the true value of this system.

16.12.2024

The Steinhauser estate in Utting shows exemplary handling of the existing building

Building design

the property of the former Steinhauser department store in Uttinger Bahnhofstrasse on Lake Ammersee to be preserved and extensively renovated. Photo: Leonard Mandl

Historic buildings that are particularly characteristic of the area have an identity-forming quality and can serve as a model for those who are still undecided. Wherever possible, existing buildings should be preserved and linked to existing residual structures. One successful example is the restoration and refurbishment of the Steinhauser estate in Utting am Ammersee in Bavaria We are familiar with the phenomenon from China: faceless and history-less satellite towns that […]

Historic buildings that are particularly characteristic of the area have an identity-forming quality and can serve as a model for those who are still undecided. Wherever possible, existing buildings should be preserved and linked to existing residual structures. One successful example is the restoration and renovation of the Steinhauser estate in Utting am Ammersee in Bavaria

We are familiar with the phenomenon from China: faceless and history-less satellite cities that offer residents nothing to identify with and old, established cities that have completely changed their shape within fifty years, so that old people no longer recognize the city of their birth. Fortunately, things are different in Europe. Efforts are usually made to preserve historic buildings, but all too often old properties stand in the way of rapid economic development. In addition, renovation can be a financial drain. That is why demolition often seems to make the most sense. But old houses have charm, give a place a specific character and reflect the local history. Restoration should therefore always be preferred to new construction, even for buildings that are not listed. However, there is often no getting around a conversion to adapt to modern living conditions.

But how to deal with the difficult-to-calculate costs, especially if the building is already in a rather precarious structural condition? Historic buildings that shape the townscape in particular have an identity-forming quality and can serve as a model for undecided neighbors. We must therefore preserve existing buildings wherever possible and build on existing residual structures. A successful example of this is the renovation of the Steinhauser estate in Utting am Ammersee. The building complex has an eventful past, reports client and architect Bettina Sunder-Plassmann: “In 1885, a Mr. Summer from Inning bought a meadow from a farmer in Utting. Because he was planning an inn on this plot, he made sure that the new train station was built right next to it. The road from the village to the station ran through fields, so the mayor at the time resorted to an unusual means: to create a landmark and encourage development along the road, he borrowed money from the local butcher and built a magnificent house with a turret in 1899. Unfortunately, the mayor was unable to repay his debts and had to sign the building over to his creditor. Unfortunately, the extensions and conversions carried out over the course of time were not always appropriate. In 1934, a flat extension was added to the building for the local bank branch, and twenty years later another house with a store on the first floor was built on the east side. At the same time, the striking tower on the main building was dismantled. Later, the colorful painted wooden sash bar windows were replaced with single-sash windows in the mahogany look of the 1970s, the shutters were removed, openings were bricked up and balconies and dormers were torn down. In the end, the building complex stood empty for more than twenty years, deteriorated visibly and eventually became Uttings eyesore.

Numerous purchase offers from the municipality and other interested parties – including those planning new five-storey buildings with maximum utilization – were rejected by the owners. Until finally, in 2017, the architects Bettina and Benedikt Sunder-Plassmann were awarded the contract for their plan to preserve the property, extensively renovate it and set up their architectural practice on the first floor. “It was clear to us from the outset that we wanted to restore the stately appearance of the Art Nouveau building,” explains Benedikt Sunder-Plassmann. The reconstruction of the balconies and the rotunda, including the tower perched on top, was essential for the planners, builders, owners and users. They used old photos and plans as a guide, but also took the liberty of transferring design and stylistic elements into a modern design language. This approach to the existing building, which respects what is there and carefully adds new elements, structures and perspectives, is known as “building on”. Some interventions were also necessary inside the building. People used to live more simply, in just one room with a washbasin and shared toilet. It was therefore necessary to adapt the floor plans to today’s needs.

In addition to a co-working space, four regular apartments and a vacation apartment were created on the upper floors. An extension was added to the rear part of the Steinhauser property, where the entrance area and bathrooms are now located. Three new pointed dormers on the south side bring light into the rooms on the top floor and even provide an exclusive view of the lake from one of the openings. In addition to the old beams, in which the year of construction is engraved, two steel girders were installed for structural reasons – an architecturally appealing dialog between old and new. The first floor of the main building and the single-storey middle building is home to a furniture store and an architectural office specializing in the renovation of old buildings. The refurbishment is also intended to send a signal to other clients that building with existing buildings is definitely worthwhile. It is also a contribution to genuine sustainability. The façade of the Steinhauser property was insulated with eight-centimetre thick hemp and wood fiber boards, reinforced and then plastered with NHL lime plaster fine from Keim. A special design element is the surrounding, color-contrasting plinth with a coarse comb plaster typical of Art Nouveau, which visually unites the three different buildings. The entire façade was painted in antique white (wall surfaces), sandstone (plinth and cornices) and gray-green (window frames). The new, triple-glazed mullioned windows made of eucalyptus wood are based on the old windows from the 1930s; one arched window from the time of construction in 1899 was preserved and upgraded, while another from the 1930s was converted into a box window. The interior also focused on quality and appropriate, ecological refurbishment. In many rooms, wall and ceiling paintings worth preserving from the time of construction were discovered under layers of paint and wallpaper.

A piece of architectural identity for the town

Conclusion: With the revitalization of the site, the owners are sending a clear signal of their architectural approach and at the same time giving the location back a piece of its architectural identity. The once run-down Steinhauser estate has become a real gem in the village. An ugly duckling has been transformed back into a proud swan thanks to the successful restoration.

Reading tip: Architects usually try to create finished houses, i.e. coherent works of architectural art for eternity. But does this claim stand up to reality? Should that even be the claim? Inspired by references from architectural history, art and anthropology, the young Stuttgart-based studio Kaiser Shen has developed various theories and tested them on the basis of its own projects. From next Wednesday, these will be presented in an exhibition at the architekturgalerie am weißenhof in Stuttgart (until October 3, 2022).

13.01.2025

Project

A water plan for Rotterdam

Building design

Waterplan 2 was intended to make Rotterdam safe from flooding and inundation and attractive at the same time.

Is it possible to see water not as an enemy, but as a friend? And what measures can be taken to ensure that Rotterdam is prepared for the future? In recent years, the city has taken a number of important steps to address these questions. The Municipality of Rotterdam, the water authorities

Hollandse Delta, Delfland and Schielend & Krimpenerwaard have jointly drawn up the “Waterplan 2”. The adaptation program “Climate Security Rotterdam” has been established and the first results of the water plan are already visible. Rotterdam used the omnipresent risk of flooding as an opportunity to create a safe, economically strong and attractive city.

Rotterdam was built on the Rotte, where it flows into the Maas. Water and Rotterdam are inextricably linked. Water has always played an important role in Rotterdam’s urban development. The streets along the canals, designed by the architect Rose, Kralingse Plas and Delfshaven are sought-after residential areas. Water is also very important for Rotterdam in economic terms. Thanks to its geographical location in the delta to the North Sea, the port has developed into an important economic engine in Europe. More and more is now being invested in innovation and the development of expertise in the field of delta technology.

As far as water is concerned, the city has a unique position. Rotterdam is surrounded by water on all sides: by the sea and by rivers; in addition, rain and groundwater levels influence the city. Two developments stand out: the higher water level as a result of rising sea levels and changing river flows; and flooding due to increasing rainfall. By 2050, 800,000 cubic meters will have to be dealt with. The city of Rotterdam wants to achieve its goals with the help of water. Its mission is to create a safe, attractive city with a strong economy. Water can make an important contribution to this. Three aspects are important here:

Rotterdam is one of the safest cities in the Netherlands. This safety is very important for the region and must be maintained. Rotterdam has chosen a strategy of adaptation, which means that the city adapts to the situation at hand. Therefore, resources are currently being saved in order to be able to strengthen the water defense later on. Water managers, urban planners and landscape architects are working on using dykes as connecting elements: as parks, as balconies with views over the Meuse or as footpaths and cycle paths. When building outside the dykes, rising water levels must be taken into account. Innovations such as floating constructions or buildings on piles can take this development into account.

International city of water knowledge

Rotterdam has a unique concentration of knowledge and economic activities in the field of delta technology. The city wants to strengthen its role as a city of knowledge. Knowledge should be further developed, combined and shared. The city also wants to distinguish itself as an international laboratory for experiments in the field of climate adaptation.

Attractive residential areas

Rotterdam is using water to make the city even more attractive. Waterplan 2 outlines what Rotterdam could look like in twenty years’ time. The characteristics of the water system and the urban structure divide the city into three areas. The first is the city on the river, which consists of the areas outside the dikes. The most characteristic feature is the river Maas, which gives Rotterdam its identity. The waterfront areas with Kop van Zuid, the Lloyd Quarter and those areas that offer space for a dynamic living and working environment characterize the city. The second area is Rotterdam North.

Many sought-after residential and working areas are located there. The aim is to further develop existing features. The canals and drainage basins are to be extended where possible and innovative solutions implemented. In the case of the third area, Rotterdam South, extraordinary solutions are needed for extraordinary problems. The area is rich in water, but it could be better utilized. A comprehensive strategy is therefore needed. The aim is to improve the water structure of Zuiderpark, open up new waterways and connect Rotterdam South with the island of IJsselmonde.

Rotterdam – the city of water

Conventional solutions are not sufficient to achieve these goals. In the dense city center and in the old districts, it is not possible to expand water reservoirs. The costs are astronomically high and existing buildings cannot simply be demolished. Here, innovations such as water squares, green roofs and alternative forms of water storage are essential for the development of the city. The water square is a central point where rainwater can be temporarily stored. After the rain, the water is slowly returned to the drainage systems, surface water or groundwater. Water squares are dry most of the year, but as soon as it rains, their appearance changes drastically.

In this way, an extraordinary public space can be created. Green roofs not only store water, they also insulate, bind fine dust and increase the ecological value of a city. They should therefore be implemented on a large scale. Until now, it has not been common practice in the Netherlands to use green roofs to retain water. In Rotterdam, around 4.6 million square meters of roof area are suitable for greening. In this way, the various water problems can contribute to a safe, attractive and competitive port city.

Rotterdam is protected now and in the future. Rotterdam strengthens its position as a city with knowledge about water. Water is used to create attractive residential areas. Through practical and long-term solutions, concrete projects, innovation and intensive cooperation between institutions and disciplines, Rotterdam will become the water city of the future.

Published in Garten + Landschaft 11/2008 – Designing with water.