What is checked in the floor structure of an old flat after strip-out?
You check the material of the beams, their section and condition, the bearings in the walls, signs of damp and biological attack, cracks and deflection. The inspection is done by a technical architect or architect while the floor structure is exposed, before new finishes go on top.
Before strip-out part of the picture is hidden: false ceiling, screed, plaster. Afterwards, a question gets settled that cannot be discussed from photos: will the floor carry the new load? And in a luxury renovation the load is higher than usual: marble flooring, a stone bath, a heavy kitchen, big aquariums, new acoustic build-ups. So the inspection happens at the start of the works, not the end, and its results shape the project.
What kinds of floor structure exist in buildings of different eras?
In buildings before the late 19th century, timber beams with boarding or with a vault. In the Eixample and buildings from 1880 to 1940, most often steel I-beams with brick vaults (voltas catalanas) or ceramic infill blocks. In the 1940s and 50s reinforced concrete beams and the first precast elements appear. From the 1960s, prestressed joists with infill blocks, and in that period aluminous cement was used, discussed below.
The type of floor determines how it is checked and what is done. Timber fears damp and insects, steel rusts, reinforced concrete degrades through rebar corrosion and, in buildings from 1950 to 1970, also through aluminosis. Eras mix within one building: the bathroom was rebuilt in the 1960s, the kitchen in the 1980s, and the floor in each zone is different.
How can you tell a timber beam is damaged?
Signs: small round holes and fine sawdust under the beam, soft wood that can be pricked with an awl or screwdriver, splits along the grain, dark damp stains, a musty smell and sagging of the floor above the beam. The most vulnerable points are the ends built into the wall and the areas under bathrooms, kitchens and old roofs.
Barcelona has termites, so the technician looks for them too: earth tunnels and beams that look whole but are hollow inside. The affected length is cut out and replaced, the beam is strengthened with a plate or a splice and the void is treated with preservative. If rot has reached the bearing, it is no longer a question of one beam but of the joint and the wall. Without the technician's inspection and a record of the condition in a report, it cannot be assessed.
What is aluminosis and how do you recognise it?
Aluminosis is the degradation of concrete made with aluminous cement (cemento aluminoso), widely used in Spanish residential construction roughly between 1950 and 1970. Over time, in damp, warm conditions, it loses strength, and structural elements can weaken without clear outward signs.
It cannot be recognised reliably by eye. Beams and floors with cracks, rust stains from the rebar, crumbling concrete and a dark colour look suspicious. The exact answer comes from laboratory analysis of samples, ordered by the technician. If a building from 1950 to 1970 has no investigation report, it is done before the project, not after. The result decides whether reinforcement is needed.
Who decides whether reinforcement is needed?
The architect or technical architect who signs the project. Not the contractor and not the owner. They assess the calculation and the condition, write the report and the reinforcement project and, if needed, bring in a laboratory. Structural work requires a project and, as a rule, a major-works licence (obra mayor), which we cover in a separate article.
The decision depends on the loads you plan. For housing, the CTE adopts an imposed load of the order of 2 kN/m², about 200 kg per square metre. A 2 cm marble floor weighs 50 to 60 kg/m², and a full stone bath several hundred kilos on a small area. So before choosing materials, consult the technician: heavy solutions sometimes require reinforcement, light ones do not.
How is a floor structure reinforced?
The methods depend on the type. Timber beams are strengthened with timber or steel plates, with splices in place of the damaged section, or with a concrete topping that acts together with the beams. Steel beams are cleaned, protected with primer and supplemented with sections or plates. Reinforced concrete is strengthened with composite materials, section enlargement or additional supports.
Each method costs something in height and weight. A concrete topping adds height and load, so walls and foundations are checked. Additional sections change the ceiling and the width of openings. There is an upside too: reinforcement often improves acoustic insulation as a bonus. The technician chooses the option according to what you want to keep: exposed beams, vaults, mouldings.
Will reinforcement stop the renovation for long?
It depends on scope: reinforcing a single beam fits the normal work schedule, while the floor of a room or a whole flat can add from a few weeks to a few months, depending on the project, approvals and materials. Figures can only be given after inspection, not from photos.
To avoid losing time, the inspection is done right after strip-out and material orders and permits are prepared in parallel. The budget is set with an allowance for hidden work. BCN YARD comes to the site, records the state of the floors, brings in a technical architect and shows the owner photos and the report before you sign any addendum. We run the project in Russian and Spanish, with one person responsible. We answer every enquiry within an hour.
Frequently asked questions
What is aluminosis and how do you recognise it?
It is the degradation of concrete made with aluminous cement, used in Spanish housing roughly between 1950 and 1970. It loses strength over time. You cannot reliably spot it by eye: cracks, rust stains and crumbling concrete are suspicious. Laboratory analysis of samples ordered by the technician gives the answer.
How can you tell a timber beam is damaged?
Small holes and sawdust under the beam, soft wood that an awl pricks, splits along the grain, damp stains, a musty smell and a sagging floor. The most vulnerable spots are the ends in the wall and the zones under wet rooms. The technician makes the final call after inspection.
Who decides whether reinforcement is needed?
The architect or technical architect who signs the project. They assess the condition and loads, write the report and the reinforcement project and, if needed, order a laboratory. Neither the contractor nor the owner decides. Structural works usually need a project and a major-works licence.
Will floor reinforcement stop the renovation for long?
It depends on scope. One beam fits the normal schedule, and the floor of a whole flat can add a few weeks to a few months, depending on the project and approvals. Exact times come after inspection. To avoid losing time, inspect right after strip-out.