In short. A self-build mortgage is not paid out in one go. It is released in tranches, against certificaciones de obra — interim certificates of work done — signed by your architect and stamped by the Colegio, the architects’ professional body. The last tranche, usually around 15 %, is held back until the certificado final de obra, the completion certificate.
This page is written from that side: the side of whoever signs the documents that make the bank pay. It is the part no bank product sheet explains, and the part that decides whether the works have cash or not.
How it differs from an ordinary mortgage
| Ordinary mortgage | Self-build mortgage | |
|---|---|---|
| Subject | A house that already exists | A plot and works not yet built |
| How the money arrives | In full on signing | In instalments, against certificates |
| Security | The existing house | The plot plus the future building, valued as if finished |
| Who certifies progress | Nobody: there is no progress | The architect directing the works |
| Grace period (carencia) | Not common | Common while the works run, up to two years |
How the money is actually released
A certificación de obra states how much of the design has actually been built by a given date, and what it is worth; the architect directing the works signs it and the bank pays against it. Bank contracts are explicit once you read them. One we have looked at provides that up to 85 % of the principal is drawn down “in line with the progress of the investment and the rate of execution”, evidenced by “certificates issued by the Architect Directing the works”, and holds back the remaining 15 % until the completion certificate “duly stamped by the Official Colegios”.
Another is clearer about the formal requirement: the degree of execution “shall be evidenced by certificates issued by the architect directing the works, stamped by the respective Colegio”. That stamp is the visado colegial: the Colegio certifies that the signatory is registered, insured and entitled to sign.
| Tranche | Indicative weight | What releases it | Who signs |
|---|---|---|---|
| Initial | 40–50 % | Deed, land registry search and the building under construction registered | The notario (a public official, not a solicitor) and the Land Registry |
| Interim | 35–45 % | A stamped certificación de obra at each milestone: foundations, structure, envelope, finishes | The architect directing the works |
| Final | 10–20 % | Certificado final de obra, stamped, and sometimes first occupancy and registration | Architect and aparejador |
Where the cash flow breaks. The bank pays against work already carried out. The builder tends to ask for money on account, or to invoice at thirty days. That gap is yours to cover, and it is the number one practical problem of a financed self-build. Better agreed with the builder before signing, not after.
Why a stamped design changes the valuation
Valuations are governed by Order ECO/805/2003, updated in 2025. Its article 4 defines the value on the assumption of a finished building as the value a building that is on the drawing board or under construction will foreseeably reach on the date it is finished, if it is built within the estimated timescale and with the characteristics of its design.
The consequence is direct, and few people spell it out:
Only the plot has value
With no stamped design and no permit, the valuer can only value the land. The figure is far lower, and so is the loan.
The finished house has value
With a stamped design and a permit, the valuer issues a value on the assumption of a finished building, and that is the base the bank calculates from. The design is not a formality: it is what multiplies the valuation.
If planning documentation is missing, or the property cannot be inspected, the valuation comes out with conditions or warnings, and with a condition attached the bank does not usually move. The updated rules also require the valuer to hold the stamped design, the permit, and the certificate of work carried out.
What technical documentation you will be asked for
- Design stamped by the Colegio
- Building permit or administrative authorisation
- The builder’s priced tender for the works
- Valuation on the assumption of a finished building
- Stamped certificaciones de obra at each tranche
- Certificado final de obra, stamped
- Deed of the building under construction, registered
- All-risks construction insurance
The ten-year insurance: what the law says and what the bank does
The law exempts you. The second additional provision of Law 38/1999 on Building Regulation (Ley de Ordenación de la Edificación, LOE) leaves out the individual self-builder of a single detached house for his own use, with the well-known exception of a sale within ten years.
The bank is another matter. It cares about being able to resell the property if it has to enforce the mortgage, and there is evidence that many lenders ask for the insurance anyway. That said: we have not found a single official bank website that requires it in writing. It is decided case by case, so ask before you sign rather than assume it is off the table.
How much they lend
| Lender | What it states | Source |
|---|---|---|
| Santander | Up to 100 % of the priced works, capped at 70 % of the replacement value of the finished construction. It does not finance the land. Grace period up to two years | Its website, consulted in August 2026 |
| BBVA | Drawdown in instalments against a stamped certificate. Publishes no percentage or maximum term in the contract | Its official loan contract |
| Another lender consulted | 85 % available in phases and 15 % held back until the completion certificate | Its official contract |
Why we do not publish a table with every bank. Tables circulate with percentages and rates for a dozen lenders, taken from comparison sites. We have not been able to confirm them on each bank’s own website, and publishing as a lender’s condition something that lender does not say strikes us as wrong. These three we have verified from a primary source.
And note what these figures are: commercial conditions each bank sets for itself, not something Spanish law fixes.
The eight real problems
Cash flow gap
The bank releases against work carried out; the builder asks for money on account. You fill that hole.
Final retention blocked
Some contracts tie the last tranche to registration at the Land Registry, not just to completion. Worth reading before you sign.
Drawdowns cut back
If the valuation falls, or you skip items that were priced, the lender can trim the tranches to come.
Budget overrun
Cost above the tender that was valued is not financed.
Design changes
They mean amending the permit, and can force a revaluation.
Late certification
Every certificate that slips is a month of interest with the works not moving.
Maximum period for the works
Contracts set one, and going past it entitles the bank to suspend drawdowns.
Works left unfinished
With no completion certificate there is no last tranche and no registration of the completed building, and the loan already drawn is repaid anyway.
What the studio can do. Almost all of these are managed from the direction of the works: certifying on time and with the visado in order, anticipating design changes instead of discovering them, and scheduling the certificates with the bank and with the builder before starting. Articles 12 and 13 of the LOE put two technicians on every Spanish site: an arquitecto for the design and an arquitecto técnico, or aparejador, for the execution. Fran Cortés holds both qualifications. A certification schedule agreed three ways heads off most of the surprises.
Frequently asked questions
Does the bank hand over all the money when I sign?
No. It comes in tranches: an initial drawdown, interim drawdowns against a certificate of work done, and a final tranche held back until the certificado final de obra. In one contract we have seen, that final retention is 15 %.
Who signs the certificates that release the money?
The architect directing the works, and the bank contracts say so expressly: “certificates issued by the architect directing the works, stamped by the respective Colegio”. Without that signature and that stamp, no tranche is released.
Do they finance the land?
It depends on the lender. Santander states on its website that it does not: it requires proof that you own the plot. Comparison sites say others include it, but we have not confirmed that bank by bank, so we do not take it as read.
How much do they lend?
The ceiling is usually the lower of a percentage of the finished-building valuation and a percentage of the works budget. Santander publishes that it finances up to 100 % of the priced works, capped at 70 % of the replacement value of the finished construction. That percentage is each lender’s commercial decision, not something the law fixes.
Do I need the ten-year insurance?
The LOE exempts the individual self-builder of a single detached house for his own use. Whether the bank asks for it anyway is another matter: it cares about being able to resell the property. We have found no official bank website that requires it in writing, so it is a case-by-case demand.
What is the carencia?
A grace period in which you repay no capital and pay interest only, and only on what you have drawn down. Santander states up to two years. It overlaps with the building period, when you are also paying rent wherever you live.
Can I apply for one without a permit?
Not with any certainty. Without a stamped design and a permit, or at least an administrative authorisation covering much of the budget, the valuation comes out with a condition attached and the bank cannot value on the finished-building assumption. That is where a stamped design multiplies the valuation.
What if the budget runs away, or the works stop?
Cost above the tender that was valued is not financed: you put that in. And works that have stopped stop generating certificates, so they stop receiving money. With no completion certificate the last tranche is not released and the completed building is not registered.
The certificates that release your bank’s money are the ones we sign
As dirección facultativa, the technicians legally in charge of the works, we issue the stamped interim certificates and the completion certificate — the documents the bank pays against. And we set up the certification schedule with the builder before work starts, so the site does not stop waiting for money.