How long does a prefab house last? Real lifespan by type

Do they last less than a conventionally built house? No, and the standards say so

In Spain, the structure of a home is designed for 50 years, whether it is prefab or built on site. That is the service period set by the Building Technical Code (Código Técnico de la Edificación) when the project does not ask for another, and the design life that the Structural Code (Código Estructural) takes as the reference for buildings.

That number is not an expiry date. It is the time the structure must serve, with its maintenance, without needing major repairs, and a well kept house goes beyond it.

The same table keeps 10 years for temporary structures and 100 for monumental buildings. And it makes clear that a structure taken apart to be put up again does not count as temporary: being prefab takes no years off.

How long a prefab house lasts by type

The same thing rules all four types: water. What changes is where it gets in and how much care each material asks for.

• •Timber: it lasts as long as it does not get wet inside. Renew the outer protective finish every 4 to 10 years, depending on the sun and rain it gets. See timber prefab houses.
• •Concrete: it does not rot and insects do not attack it; it is enough to seal cracks and joints before water reaches the steel inside. See concrete prefab houses.
• •Steel (steel frame): the galvanising barely wears inside a dry wall, and much faster with condensation or near the sea. See steel prefab houses.
• •Container: it is steel exposed to the weather; it needs anticorrosion paint and a thorough check every 5 to 10 years. See container houses.

In all of them, the roof and the joints are checked every year: water that gets in unseen is the worst enemy of any house. The full schedule is in prefab house maintenance.

What guarantee you have: the law's and the manufacturer's

Lifespan is estimated; a guarantee is signed. There are two, and they add up:

• •The legal one, if the house is real estate (with a project and a permit). The Building Act (Ley de Ordenación de la Edificación) makes the builders liable for 10 years for the structure, 3 for anything affecting habitability and 1 for finishes, just as with a conventionally built house. Those 10 years of structure come with ten-year structural insurance (seguro decenal), unless you develop the house yourself to live in it.
• •The manufacturer's, which is commercial and separate. The most common is 10 years, followed by 5, and the median is 10 years (426 houses). There are 48 houses with 30 years or more.

Get it in writing and check what each period applies to: a long figure may cover only the structure. If the house is sold as movable property (a mobile home or one on wheels), the building law does not cover it; the difference between movable property and real estate is explained in mortgage for a prefab house.

What to ask before buying so that it lasts

Ask about water before asking about the material: almost everything that shortens a house's life gets in that way.

• •What protection the outside timber has. The Building Technical Code requires the structure to be treated for the moisture it will bear (it calls this the use class).
• •Whether the system suits your climate. Near the sea, steel and containers suffer more; where it rains a lot, timber needs a design that keeps it away from water.
• •How it prevents condensation: insulation, ventilation and vapour barrier.
• •What maintenance the guarantee requires, in writing.

With those answers, compare models and manufacturers.