Short answer. Have it undone at the tenant's expense. Article 1168 provides that when the obligation consists in not doing and the obligor does what has been forbidden him, it shall also be undone at his expense. Violating a lease condition is also a ground for judicial ejectment.

What the law says

When the obligation consists in not doing, and the obligor does what has been forbidden him, it shall also be undone at his expense.

Civil Code, Article 1168 — Obligations Not to Do. Read the full provision →

Undoing at the tenant's expense

Article 1168 is the negative counterpart of an obligation to do: When the obligation consists in not doing, and the obligor does what has been forbidden him, it shall also be undone at his expense. A clause forbidding structures, partitions or extensions is exactly such an obligation, and the remedy is removal charged to the tenant, not merely damages measured in money. Note the practical restraint in that: it is a remedy the law gives, obtained through the courts, and a lessor who demolishes the structure himself over the tenant's objection turns a strong position into a disputed one.

Or end the lease instead

Article 1673 lets the lessor judicially eject the lessee for, among other causes, violation of any of the conditions agreed upon in the contract, and where the lessee devotes the thing leased to a use not stipulated which causes its deterioration. A prohibited structure sits squarely within the third ground. Article 1659 offers the alternative: where a party does not comply with his obligations, the aggrieved party may ask for rescission of the contract and indemnification for damages, or only damages, allowing the contract to remain in force. So you may keep the tenant and charge him, or end the lease — but choose, and say which in your demand.

Do not let it become an improvement claim

Delay is what costs landlords here. Article 1678 provides that where a lessee makes useful improvements in good faith, suitable to the use intended and without altering the form or substance of the property, the lessor at the end of the lease must pay half their value or let the lessee remove them. A structure built against an express prohibition is not made in good faith, and a landlord who objects promptly and in writing keeps it that way. Silence while the work goes up — or worse, acceptance of an increased rent for it — is what turns a breach into a claim against you.

The letter to write today

Photograph the structure with dates, then send a written demand quoting the clause that forbids it, requiring removal and restoration within a stated reasonable period, and reserving your right to have it undone at his expense and to claim damages. Say expressly that you do not consent to the works and are not treating them as improvements. Keep the lease, the turnover condition report or inventory, and every reply. If the tenant refuses, the same file supports either an action to have the structure removed or one for ejectment.

Cases citing this provision

These Supreme Court decisions cite the provision above. We list them so you can read them yourself; the summaries of what each decided are not ours to give.

Related provisions

Note. Statute text quoted on this page is reproduced from the official enactment and is linked to the full provision. The explanation around it is general legal information from Vivas & Nobles Law Office, not legal advice. Whether it applies to your situation depends on facts only a lawyer reviewing them can assess.