The first figure is almost never the right one. When a client asks how much it costs to design a home, they are actually asking several things at once: how much a well-executed idea is worth, how much it costs to coordinate it until it works, and how much the level of customisation influences the final result. It is not a fixed fee, because not all homes require the same things.

Designing a home is not just about drawing plans or choosing materials. It involves reading the space, identifying its potential, organising circulation, adjusting proportions, working with light, solving storage issues, integrating services, and turning a series of scattered decisions into a coherent proposal. That is where the price varies: not solely by square metres, but by complexity, ambition and scope.

How much does it cost to design a home depending on the brief

The most accurate way to understand the cost is to separate the design service from the construction cost. They are two distinct items, although they are closely related. The design defines what is to be done and how it is to be done. The construction brings that decision to life.

In Spain, design fees for a home tend to vary across several models. Some practices work on a price per square metre. Others apply a percentage of the construction budget. And for very well-defined projects, a fixed rate broken down by phases may also be considered.

As a rough guide, an architectural and interior design project can account for between 8% and 15% of the construction budget, depending on the level of service. If it is a partial project, with less technical complexity and less detailed development, the percentage may be lower. If we are talking about a bespoke home, with custom-made furniture, intensive coordination and full project management, it may be higher.

When calculated per square metre, many residential commissions fall within a range of approximately €40 to €120 per square metre for design fees alone. This range is deliberately broad. It does not cost the same to reorganise an 80 m² flat using standard solutions as it does to design a detached house with a bespoke layout, material research, custom joinery and comprehensive project management.

What the price actually includes

When comparing quotes, the most common mistake is to assume that all firms offer the same thing. This is not the case. Two proposals may have similar prices yet cover completely different scopes of work.

A basic commission usually includes data collection, a layout proposal, general plans and an initial definition of materials. It is useful for a simple project or for a client who wishes to take charge of part of the process themselves.

A more comprehensive service incorporates concept design, technical development, visualisations or supporting documentation to visualise the project, interior design, specification of finishes, joinery, bathrooms, kitchen, lighting, measurements, coordination with contractors and site supervision. Here, the value lies not only in the drawings, but in reducing the need for last-minute decisions and ensuring the final result is not compromised.

The more detailed the project, the less room there is for ambiguity during execution. This does increase fees, yes, but it also tends to improve control over deadlines, actual costs and perceived quality.

Basic design, full design or comprehensive service

Not all clients require the same level of support. In an investment property, for example, it may make sense to optimise timelines and focus the design on layout, durable materials and a clean, uncluttered aesthetic. In a primary residence, however, personalisation, everyday comfort and meticulous attention to specific uses usually take precedence.

The comprehensive service is more suitable when a coherent vision of the whole is desired. Architecture, interior design and construction cease to function as separate elements and begin to respond to a single spatial logic. That continuity is evident in the result.

The factors that most influence the cost of designing a home

Size matters, but not as much as it seems. A small, heavily modified flat may require more design hours per square metre than a larger, simpler home. The real challenge lies in the number of decisions and the level of precision the project requires.

The type of property is one of the primary factors. It does not cost the same to design a new home as it does to renovate an existing one. With new-builds, there is greater freedom to structure the space from the outset. With renovations, however, there are pre-existing constraints: structure, old installations, ceiling heights, the owners’ association, regulations and potential surprises during the build. This context adds to the time required for planning and coordination.

The layout also carries significant weight. If the brief is simply to update finishes, the scope of work will be more limited. If it involves completely reconfiguring the kitchen, bathrooms, and day and night zones, the technical complexity increases. The same applies to lighting, climate control, or the design of bespoke elements.

Another decisive factor is the degree of customisation. A home with well-chosen standard solutions can be excellent whilst keeping design costs in check. But when the project relies on exclusive details, built-in furniture, bespoke joinery or a very defined aesthetic narrative, the development hours increase.

Communication also plays a part. Some clients are very clear, quick to make decisions and aligned with a design direction from the outset. Others need to explore more options, compare alternatives or adjust the project in phases. Neither situation is better or worse, but they do affect the time invested and, consequently, the cost.

Renovation or new build: price differences

In terms of design, a renovation is usually less predictable. For this reason, for the same floor area, it often requires more intensive work. It is necessary to measure precisely, understand the existing structure, identify limitations and make decisions that reconcile aesthetic ambition with construction realities.

In new-build projects, the design may be cleaner from a technical point of view, though not necessarily cheaper. If the property is being built from scratch and a highly bespoke solution is sought, the number of decisions to be made is enormous: volume, orientation, structure, materials, interiors and the relationship between architecture and use.

The real difference lies not only in whether you are renovating or building from scratch, but in how much detail is expected from the practice and the extent of its role within the process.

How to read a quote without focusing solely on the figure

A well-structured design quote should explain the phases, deliverables and scope. If you do not understand what is included, it will be difficult to compare. The useful question is not just how much it costs, but what problem that amount solves.

It is worth checking whether the fees cover site surveys, alternative proposals, technical development, material selection, site visits, coordination with consultants and the number of revisions. Also, whether administrative procedures, structural calculations, licence management or project management are excluded, where applicable.

Sometimes a lower quote ends up costing more on site. This happens when the project is poorly defined, solutions are improvised on the fly, or constant changes arise due to a lack of foresight. In homes with certain standards, design should not be seen as an upfront cost, but as the tool that organises everything else.

The balance between investment and value

It is not always advisable to opt for the most comprehensive package, but rather the right one. If the aim is to optimise a property for sale or rent, a precise and well-targeted intervention may suffice. If the home is intended to reflect a specific way of living, entertaining, working or relaxing, the project requires greater depth.

It is in striking that balance between investment and value that a specialist studio makes the difference. Good design does not add unnecessary layers. It selects, simplifies and shapes a space that functions better and is perceived better.

So, how much does it realistically cost to design a home?

If you’re looking for a quick figure, the honest answer is this: it depends on the scope, but it should rarely be assessed solely by square metres or a standard rate. For a small home requiring partial work, fees can start at a few thousand euros. For a comprehensive renovation or a highly customised home, the cost rises in proportion to the work involved in definition, coordination and detail.

For clients who value design, spatial quality and consistent execution, the useful question is not how much a plan costs, but how much it is worth making good decisions before building. That is the difference between a decent home and a home that has truly been thought through.

In practices such as FFWD Arquitectos, where architecture and interior design are understood as a single project, the cost reflects this logic: bespoke solutions, functional clarity and a spatial language that is not improvised. That investment translates into order, identity and a better experience of the space.

If you are evaluating your project, the most sensible approach is to request a proposal tailored to your specific situation. Not to obtain a generic figure, but to understand what the home needs and what level of design it deserves. When the approach is precise from the outset, the budget ceases to be an unknown and begins to become a criterion.