Building a house in Spain: how to work out the full budget

Check what the plot allows before choosing the house

Before buying land or committing to a house model, establish the plot's planning status and what can be built on it. Its access, slope, ground conditions, available utility services and restrictions can all affect the design and cost. An empty plot is not necessarily ready for construction.

Obtain the relevant municipal information and technical advice, with studies and checks that relate to the intended project. Spain's Ley de Ordenación de la Edificación sets out roles and responsibilities in building projects, including those of the promotor, the person or organisation commissioning the development. Planning a home therefore involves decisions and responsibilities beyond selecting a design from a catalogue.

Official source: BOE · Ley 38/1999 de Ordenación de la Edificación

Establish which floor area and specification the price uses

Check whether each rate is based on usable floor area, built area or another measurement. Ask how porches, terraces, garages and basements are counted. Two rates per square metre cannot be compared directly if they use different areas or cover different types of space and work.

Ask what will be complete at handover: the structure, external walls and roof, heating, plumbing and electrical systems, finishes, kitchen, lighting and other equipment. A turnkey offer still needs an itemised specification. For a prefabricated house advertised at a factory price, establish the cost of transport, assembly, access and work on the plot before comparing it with a complete building proposal.

A worked example: costs left out of a €180,000 quote

In this hypothetical example, the initial construction offer is €180,000. Four groups of necessary costs, totalling €38,000, sit outside that offer. Adding them and a chosen contingency of €18,000 produces a budget total of €236,000. These figures illustrate the method; they are not current market prices or costs from a completed customer project.

Land purchase, taxes and finance are still excluded from this total and would need to be assessed separately. The extra items are added only because the example assumes the initial offer leaves them out. Check your own contract so that an included cost is not counted twice.

• Add the plot purchase and associated expenses if you do not already own the land.
• Calculate the project's applicable taxes, municipal fees and other charges separately.
• Allow for financing, temporary accommodation and any choices still awaiting a price.

Keep agreed prices, estimates and unknown costs separate

Use three columns for the budget. The first contains work with an agreed scope and contract price. The second contains estimates, each with the assumptions behind it. The third lists decisions or checks that have not yet been priced. Keep that last column visible; leaving unknown costs out of the total does not make them disappear.

Specify materials and measurable performance, quantities, anything left out of the price, dates, payment stages and the process for changes. Ask what happens if ground conditions require a different solution or you choose different finishes. Before a variation is carried out, its reason, cost and effect on the timetable should be set out and agreed.

Have the relevant tax treatment checked for each type of cost. Land, professional fees and construction cannot simply be grouped together under an assumed single tax rate. Confirm municipal costs too. The aim is to establish the full amount you must pay, using clearly separated costs and the correct treatment for each.

Adjust the design if the complete budget is too high

With the technical team, compare a smaller floor area, a simpler building shape or postponing work that can be completed later without redoing finished parts. For each change, identify the saving and what you would lose in use or space. Cheaper visible finishes may do little to offset an unnecessarily complex design, and cuts made without considering the whole project can create costs later.

Keep a version you can fund under prudent assumptions. Show desired upgrades as separately priced options. Use the contingency for uncertainties, while including known necessary work in the main budget. A reserve cannot make an incomplete proposal reliable if substantial requirements have simply been omitted.

Compare prefabricated and conventional homes on equal terms

Compare proposals for the same plot, equivalent performance and the same level of completion. A general claim that one construction method is cheaper is not enough. For a prefabricated option, identify what is completed in the factory, what remains to be done on site and what access, transport and assembly require.

Establish who is responsible for each part and how the designers, suppliers and contractors will coordinate. A catalogue price can be a legitimate starting figure while leaving out substantial costs specific to the land. Have those costs explained before using the headline price to choose a building system.