Establish feasibility before the purchase becomes irreversible
Buying to renovate involves two connected transactions: acquiring an existing property and delivering a transformation that does not yet exist. The attractive purchase price may depend on extending the home, converting commercial premises or incorporating a terrace. If that transformation is not permissible, the original financial comparison falls apart. Record the outcome you genuinely need and the improvements you could abandon without abandoning the purchase.
Commission a technical inspection with access to the relevant spaces and provide the available registry, cadastral and municipal records. The professional should distinguish conclusions possible through visual inspection from matters requiring measurements, opening-up work, calculations or administrative enquiries. An initial survey cannot guarantee that no surprises will emerge, but it can separate manageable uncertainties from obstacles that fundamentally change the project, its cost or the completion programme.
Legal framework and sources: BOE — Código Técnico de la Edificación ↗BOE — Ley de Ordenación de la Edificación ↗
Separate the physical building from its lawful position
A garage used as a bedroom still needs its permitted use checked. An enclosed terrace may feature prominently in the viewing without being lawful residential floor space. Compare the physical property with the deed, Land Registry, Cadastre, plans and permissions, then ask the technical adviser to explain the discrepancies plainly. Agreement between the Cadastre and the existing building does not by itself establish planning legality.
The age of a structure also does not automatically confer a right to extend or rebuild it. Territorial legislation and planning rules may restrict conservation, structural works or replacement. If your project first requires an existing alteration to be regularised, identify the procedure, evidence, cost and realistically achievable outcome. Do not purchase an expectation of legalisation supported only by assurances that similar work has always been accepted in the neighbourhood.
Legal framework and sources: BOE — Código Técnico de la Edificación ↗BOE — Ley de Ordenación de la Edificación ↗
Permissions, responsible declarations and protected buildings
The correct procedure depends on the location and intervention. Redecoration raises different issues from structural alterations, new openings, roof replacement, subdivision or a change of use. Some works require a project and licence; others may proceed through a responsible declaration where the competent rules allow it. Filing a form does not turn prohibited work into permitted work or remove technical requirements.
Check heritage protection, sector-specific restrictions and development rules. A protected façade can constrain windows, joinery or external equipment even where internal alterations appear straightforward. Seek a municipal response addressing a concrete description of the proposed works and identify every authority involved. Where feasibility is essential to your decision, negotiate time to obtain that evidence before final commitment and agree which document will count as sufficient confirmation. An informal conversation rarely provides the same certainty.
Legal framework and sources: BOE — Código Técnico de la Edificación ↗BOE — Ley de Ordenación de la Edificación ↗
Common elements and community decisions
In a building governed by horizontal property, owning a flat does not give unrestricted control over everything around it. Structure, façades, roofs, shared pipes and some terraces may be common elements even where their use is exclusive. The Horizontal Property Act allows certain internal modifications without undermining safety, structure, external appearance or others' rights, and requires works to be notified to the community's representative.
Other interventions need specific resolutions and sometimes administrative permission. The required majority depends on the actual work; neither unanimity nor a simple notification is the universal answer. Review the constitutive title, community rules and minutes, then present a sufficiently defined proposal. Organise contractors' access, lift use, waste removal and protection of shared areas within the works programme. These practical arrangements must not be mistaken for the legal approval the intervention may separately require.
Legal framework and sources: BOE — Ley de Propiedad Horizontal ↗
From an indicative quote to the complete cost
Obtain comparable quotations using the same measurements and specifications. Separate demolition, structure, services, insulation, finishes, equipment and supply certification. Clarify exclusions, taxes, professional fees, permit charges, waste management and temporary accommodation. A price per square metre may help an initial comparison, but it does not explain the cost of defects, accessibility improvements or obsolete installations.
Tie your contingency to specific uncertainties, such as an uninspected roof, concealed wiring or ground conditions that have not been investigated. Distinguish committed expenditure, provisional allowances and optional upgrades. Also test cash availability: purchase, tax and construction payments may fall due before finance is released or another asset is sold. A useful budget explains what completion will cost, when money is needed and which amounts still depend on outstanding investigations, rather than presenting a single apparently precise total.
Legal framework and sources: BOE — Código Técnico de la Edificación ↗BOE — Código Civil, contratación, compraventa y mandato ↗
A works contract that controls changes
Identify the contractor, authorised representative, relevant insurance and responsible team. Incorporate the project, quantities, specifications and programme as consistent contract documents, establishing which takes priority if they conflict. Define material supply, key custody, permitted subcontracting and the contractor's required documentation. The agreement should describe the actual commission rather than rely on a broad label such as complete refurbishment.
Changes need a written procedure stating the proposed variation, reason, cost, timing impact and prior approval by an authorised person. Distinguish a genuinely unexpected condition from an item omitted from a fixed quotation. Agreeing this process avoids a later argument about whether an informal site conversation authorised thousands of euros of additional work. Where the contractor requests a substantial advance, examine its commercial justification, any security available and the resulting financial exposure before accepting it.
Legal framework and sources: BOE — Código Civil, contratación, compraventa y mandato ↗
Link payments to verified progress
Arrange payment certificates against work actually completed and checked by the person supervising the project. An invoice and the contractor's photographs are useful evidence, but they do not replace proportionate verification of quantities and quality. Avoid paying almost the entire price while essential installations, testing or documents needed to use the property remain outstanding.
A defects retention or other security can be negotiated with a proportionate amount, duration, claims process and release conditions. There is no automatic statutory retention figure for every refurbishment. Define delay, justified extensions, suspension and termination as well. If the programme depends on permissions or specialist materials, convert it into realistic milestones. Check that your payment obligations do not require funding stages the contractor cannot yet perform, and identify who can approve a certificate when you are away.
Legal framework and sources: BOE — Código Civil, contratación, compraventa y mandato ↗
Handover, defects and completion documents
At completion, inspect the works, test installations and prepare a defects schedule. Describe each issue, responsible person and correction date. Avoid unqualified acceptance where significant matters remain unresolved. Collect final drawings, certificates, manuals, warranties, invoices and required administrative records. If floor area, legal subdivision or use has changed, investigate the corresponding registry, cadastral or occupancy updates.
The Building Act distinguishes structural damage, habitability defects and execution or finish defects, with different periods and conditions. Not every minor repair automatically falls within that regime, and those periods are not all deadlines for issuing proceedings. Contractual remedies may matter alongside statutory ones. For a serious defect, preserve evidence and obtain advice promptly. Repairing everything before documenting the condition can make it harder to establish the cause and responsible party, even when immediate protective work is necessary.
Legal framework and sources: BOE — Ley de Ordenación de la Edificación ↗BOE — Código Civil, contratación, compraventa y mandato ↗BOE — Certificación energética de edificios ↗
Example: inexpensive premises are not necessarily a viable home
Fictional example: a buyer finds commercial premises for €140,000 and receives a €55,000 quotation to convert them into a home. The combined figure appears lower than the price of a finished apartment. However, the proposal needs a change of use, adequate ventilation and alterations to a shared façade. None has been confirmed, and the quote excludes professional fees, permit charges and drainage adaptations.
The sensible next step is a technical feasibility study and municipal enquiry, a review of community approval, and a complete budget. If the purchase remains attractive, the agreement can include an objective feasibility condition and an appropriate investigation period. If the seller will not agree, the buyer must assess the purchase as commercial premises with an uncertain conversion possibility, rather than as a home whose only outstanding decision concerns the finishes.
Legal framework and sources: BOE — Código Técnico de la Edificación ↗BOE — Ley de Ordenación de la Edificación ↗BOE — Ley de Propiedad Horizontal ↗
Your purchase decision should also consider the eventual exit
Consider how the renovated property will eventually be sold or financed. An attractive refurbishment with incomplete documentation can reduce the buyer pool, complicate valuation or reopen problems thought to be resolved. Keep properly identified invoices and distinguish maintenance from improvements to assist later tax reviews, without assuming that every expense receives identical treatment.
Before committing, request an integrated conclusion covering the feasibility of the intended result, necessary permissions, technical risks, complete cost and programme. It should identify established facts and conclusions that remain conditional. Buying to renovate works best when uncertainty is located, understood and budgeted, rather than hidden behind an appealing image of the finished home. The documentation you create during the project becomes part of the asset you will later need to demonstrate and defend.
Legal framework and sources: BOE — Código Técnico de la Edificación ↗BOE — Ley de Ordenación de la Edificación ↗BOE — Código Civil, contratación, compraventa y mandato ↗
Sources & further reading
BOE — Código Técnico de la Edificación ↗BOE — Ley de Ordenación de la Edificación ↗BOE — Ley de Propiedad Horizontal ↗BOE — Código Civil, contratación, compraventa y mandato ↗BOE — Certificación energética de edificios ↗Editorial preview: professional legal review is pending. This guide provides general information and does not determine the legal position of a particular property.
Have a property in mind?
Bring the documents and questions from this guide into your property analysis.