Timber, steel or concrete frame house: how to choose the system

Timber frame house: three houses with the same name

A house with a timber frame can be three different things, and it is worth knowing which one you are being offered before comparing prices.

• •Light timber frame (in Spanish): timber studs with the insulation inside the wall, light and assembled dry. It is the system with the most manufacturers; the Senmar T3 (in Spanish) is an example.
• •Solid timber or logs (in Spanish): the wall is the timber itself, warm and solid. If you are going to live in it all year, ask what insulation is added: the plank alone is not enough.
• •CLT (in Spanish) (cross-laminated timber): solid panels of crossed layers, very airtight. It is still scarce in Spain: there are few factories (five) and much of that timber is imported.

The models are in timber prefab houses.

Steel structure: from the steel frame to the mobile home

“Steel” covers houses that have nothing in common.

• •Steel frame (in Spanish): the same skeleton as the light timber frame, but with light galvanised steel profiles. As steel conducts heat, ask whether the insulation wraps the profiles on the outside.
• •Steel modules: boxes of profiles that arrive almost finished from the factory, such as the Cube 150 (in Spanish).
• •Mobile home and sandwich panel: panels with an insulating core on a chassis, quick to install. If it is going to be your home, first check how it is financed in mortgage for a prefab house.
• •Shipping container: the same steel, with the shape and size of a shipping container.

The models are in steel prefab houses.

Concrete: the closest thing to a conventionally built house

Precast concrete arrives as panels or as reinforced concrete modules, such as MCCM's 115 m² house with terrace (in Spanish), and it is the closest thing to a traditional house.

• •Its mass stores heat and releases it slowly (thermal inertia): it softens the heat of the day and the cold of the night, and it pays off more where that difference is large than in a weekend house.
• •Before choosing it, check the access to your plot: its parts need a large lorry and a crane, and with poor access the work becomes more expensive or unfeasible.

The models are in concrete prefab houses, and the system, in precast concrete (in Spanish).

Modular house or panels: the other decision

Modular is not a material: it is how the house arrives. A modular house leaves the factory in almost finished boxes (timber, steel or concrete) that are joined on the plot on foundations already built. A panel house arrives as walls and floors that are assembled there.

• •The module leaves very little work on the plot, but each box travels by lorry: if it exceeds the normal road dimensions it needs a special traffic permit, and the lorry and the crane must be able to reach the plot.
• •Panels travel flat and get into a plot with difficult access more easily.

Those that arrive assembled from the factory are in modular houses.

How much the price per square metre changes with the frame

Concrete costs considerably more per square metre than timber (60 % more, comparing turnkey houses). Containers stay at 1,639 €/m² (25 houses from 3 manufacturers).

If you are going to assemble it yourself or with your builder, timber has plenty on offer as a kit: the parts of the house, to be assembled, without foundations or finishes, at a kit median of 403 €/m² (132 houses from 8 manufacturers). Concrete is not sold as a kit: its heavy parts are assembled by the manufacturer with a crane. Do not put the price of a kit next to a turnkey one: it is a different purchase, with the building work still to be paid.

By size and by what each price includes, cross the figures in the price per square metre comparison tool.

Can you live in it all year? Insulation decides

Yes, with any of the three. The Building Technical Code sets every new home the same limits for insulation and air leakage according to the climate of its area, whatever the material. What separates a comfortable house from one that is not:

• •the thickness and quality of the insulation;
• •air not leaking through the joints, and no thermal bridges;
• •the windows and the ventilation.

Ask about the energy rating and the insulation of each wall (more in insulation in timber houses). And how long each one lasts, in how long a prefab house lasts.