Do prefab houses need different maintenance?

One check a year, whatever the type

Any house, prefab or conventionally built, needs a check once a year: the roof, the gutters and downpipes, and the joints and seals of doors and windows. Use it to look for damp patches inside as well.

It is the task that pays off most, because water that gets in unseen is what shortens a house's life the most. Everything else depends on the material and, above all, on what the house has on the outside. How long each type lasts with this care is in how long a prefab house lasts.

Exposed timber: the protective finish, every few years

If the timber is left exposed, its outer protective finish is renewed every 4 to 10 years. The Spanish association of timber house manufacturers (AFCCM) and AMYC speak of 4 to 5 years with an open-pore stain (lasur); GoPrefabricadas gives 5 to 10, depending on how exposed the house is. The façade that gets the most sun, rain and wind is the one that needs it first.

• •Every year: outer finishes, joints and seals.
• •Every decade: a check of the structure.
• •Always: watch for damp and for signs of wood-boring insects.

The factory treatment against fungi and insects is not repeated. More in timber prefab houses.

Not every timber house needs staining: it depends on what it has on the outside

Timber can be the structure without being the façade, and what you maintain is the façade. If it is clad in fibre cement, render or external insulation (ETICS, an insulation layer on the outside with its own finish), there is no timber to treat.

• •The Vitoria by Daype (in Spanish) is sold with pine boards and one coat of stain, or with Canexel or fibre cement, which the manufacturer describes as maintenance free: the same house with two schedules.
• •The Duero by American Building System (in Spanish) covers its timber walls with ETICS and single-coat render or cement boards.
• •The other way round, the Lara 102 by SORT-7 (in Spanish) has a steel frame and stained fir boards on the outside: that one does follow the timber schedule.

A timber porch or shutters still need their protective finish. Ask what is on the outer face of the wall.

Concrete: seal before water gets in

Concrete needs very little: it does not rot, insects do not attack it and it has no fixed schedule. The job is to leave water no way in.

• •Clean and seal the façade so that damp and mould do not build up.
• •Seal cracks and joints as soon as they appear: that is how water reaches the steel inside, which is what really damages it.
• •Check the roof waterproofing during the yearly check.

Brands that work with this system are in concrete prefab houses.

Steel (steel frame): the structure is not painted, it is kept dry

The steel in a steel frame is galvanised and sits inside the wall, so it is not painted: it is kept dry. For it to rust, moisture has to stay trapped inside, from a leak or from condensation.

• •Every year: clean gutters and downpipes, check flashings and the edges of doors and windows, and make sure there are no damp patches inside.
• •Every 3 to 5 years, renew outer seals that have aged and go over paint, cladding and the fit of doors and windows.
• •Always: make sure the vapour barrier and ventilation keep doing their job.

Near the sea, salt wears the galvanising away faster. More in steel prefab houses.

Container: rust, every six months

A container house is steel exposed to the weather, and it is the one that needs most watching. Rust starts at the weak points: welds, corners, door frames and the corrugated roof.

• •Every six months, a rust check; every three if it is near the sea, and always after a storm.
• •Every 5 to 10 years, a thorough inspection.
• •Every 8 to 10 years, a full repaint: epoxy primer and a polyurethane or marine enamel finish, with extra coats on edges and welds.
• •Always: insulation, vapour barrier and ventilation, so that condensation does not stay inside, because steel does not breathe.

Options in container houses.

What the law and the guarantee expect from you

In Spain, the Building Act (Ley de Ordenación de la Edificación) requires the owner to keep the house in good condition through proper use and maintenance.

• •Ask for the building logbook (libro del edificio). If the house is real estate (with a project and a permit), it is handed over when the works finish, with the instructions for use and maintenance: that is your schedule.
• •Keep the invoices. The legal guarantees (10 years for the structure, 3 for habitability and 1 for finishes) do not cover damage caused by the owner, and maintenance that was never done can fall under that.
• •The manufacturer's guarantee is separate: SORT-7, for example, hands over its guarantee certificate with maintenance rules. Ask for them in writing before signing.