Termites and woodworm in old Barcelona house renovations: detection and treatment

How do you check a house for termites before buying?

The check is done before signing the arras: an independent pest control specialist inspects the timber elements, measures moisture and opens a few points. The result must be in writing. It costs less than replacing a floor structure and gives you a bargaining argument.

What to ask the inspection to cover. All timber beams and their ends in the load-bearing walls, door frames, skirtings, stairs, window frames, parquet on battens. Moisture readings of the wood and the walls, because termites like damp. Tapping and probing with an awl: sound wood lets the awl in no more than a millimetre or two; infested wood gives way. If in doubt, ask for a drill-resistance probe of the beam or an endoscope. In the purchase contract or the arras, include a condition: the buyer may withdraw or renegotiate the price if the inspection finds infestation. The wording is agreed with a lawyer.

An inspection is not a guarantee. Colonies live underground and inside walls, and sometimes the damage shows only after demolition. So when buying for a full renovation, a reserve is set aside for replacing part of the floor structure. There is more on how to inspect an old flat before buying in a separate article.

How do termites differ from woodworm?

They are different insects with different symptoms. Round or oval holes in wood, usually dry, are left by woodworm (carcoma), not termites. Termites eat wood from the inside and leave a thin outer shell with a hollow interior.

Woodworm: exit holes of 1 to 3 mm, with very fine frass beneath and a faint rustle in silence. It attacks furniture, doors, parquet and beams, but usually works slowly, over years. Termites: the subterranean Reticulitermes (two species are described in Spain, R. grassei and R. banyulensis) live in underground nests and reach the wood through earth galleries. Signs: mud tubes on a wall or beam, wood that sounds hollow, cracks and sagging floors, winged individuals in spring near windows and lamps. They are hard to see, and the damage is often found when they have been at work for months or years (data from Madrid's public health department; link in the sources).

For you the difference is practical. Woodworm is often treated by treating the wood, and the structure is sometimes kept. With termites the whole house and its walls, the neighbours and the ground must be checked, because the colony is not limited to your flat. A suspicion of termites is confirmed by a specialist from a sample, not from a photo found online.

What should you check in an old Barcelona house?

Look where timber meets damp: beam ends in external and party walls, the ground floor and basement, beneath bathrooms and kitchens, by patios, by old risers. These spots are the most affected because damp attracts both termites and fungus.

In Eixample and city-centre buildings put up before roughly the early twentieth century, the floors are often timber: joists (viguetas) with ceramic infill (revoltón), sometimes with timber boarding. Later buildings more often have steel sections or concrete, but mixed solutions occur, and the exact build-up shows once the ceiling is opened. Check also timber doors and frames, built-in wardrobes, skirtings, parquet on battens, the staircase and balcony slabs with timber supports.

Order of inspection. Papers: whether there is an ITE report (the building's technical inspection), owners' community minutes on earlier treatments and leaks. Visual inspection with a torch. A moisture meter. Tapping. Selective opening under the ceiling and at the end of a beam. In a renovation this is done at the inventory stage before demolition and documented with photos; the neighbouring article on beams and floors of an old flat describes what the specialist looks at after demolition.

What if there are termites in the floor beams?

Do not treat it yourself and do not close it up with new finishes. The order is: confirm the diagnosis, assess the structure, treat, replace what is damaged, remove the damp, and monitor.

The diagnosis is made by the pest control specialist: species, extent of damage, source. Then the structural check: the aparejador or a structural engineer assesses how much section remains in each beam. If a beam has lost a lot of section, temporary props (apuntalamiento) go in until it is replaced. Treatment depends on the case: injection of product into the wood and masonry along the beams, a barrier in the ground, bait stations with monitoring. Infested lengths are cut out and replaced with new treated timber, a steel section or reinforcement (side plates). The cause of the damp that started it is removed without fail; otherwise the treatment will not last.

A colony does not know the limits of a flat, so treatment is coordinated with the neighbours and the building manager. After the works you need a written report and a schedule of follow-up inspections over one or two years. Ask the firm for a document of the treatment carried out, the list of products applied and the warranty terms in writing; term and coverage depend on each firm.

Who pays for treatment: the owner or the community?

It depends on where the termites are and what is affected. The community maintains the common parts of the building; the owner maintains the home. In Catalonia the Spanish Horizontal Property Law (LPH) does not apply; book five of the Catalan Civil Code does, and it addresses this in two places: article 553-38 obliges the owner to keep their own unit and the services in it in good condition, and article 553-44 obliges the community to keep the common elements structurally sound and safe, and the owners to bear the necessary upkeep and repair works.

In practice. Structural elements of the building, including floor beams and load-bearing walls, are usually common, while the floor and ceiling finish inside the flat belongs to the owner. If the termites are in a beam between floors, the matter goes to the building manager and is settled under the community statutes and a technical report that fixes the boundary of responsibility. If only a piece of furniture, a door or the parquet in your flat is affected, you pay. If the infestation came from your flat and you knew and did not act, liability towards the neighbours is possible.

What Barcelona City Council requires for termites is confirmed with the district office and the Agència de Salut Pública. Analysing a particular case is a job for a lawyer or the administrador de fincas, not for an article.

Can old beams be kept after treatment?

Yes, if enough sound section remains after treatment. The decision is made by the aparejador or structural engineer from measurements, not from how the wood looks. Often the beam is kept and the weak lengths are reinforced.

Reinforcement options: steel side plates, additional beams alongside (sistering), epoxy-bonded rods, replacing beam ends in the wall with a steel shoe support. After reinforcement the timber is brushed, treated with a preservative and protected from damp, because moisture remains the main source of reinfestation. If the beams stay exposed, they are finished with oil or wax, and fire resistance requirements are checked against the project.

What goes wrong. The ceiling is closed with new finishes without checking the beams: the attack continues hidden and a finished surface has to be opened. The wood is treated and the leak is not fixed. Infested parquet is left on old battens. For a luxury project with historic beams the right order is: opening-up and diagnosis before the concept design, then deciding what is retained. That puts into the budget and schedule what is usually called a "surprise".

How BCN YARD works with old timber in a house

We start with an inventory before demolition: we photograph the timber elements, mark damp spots and open check points. If signs of termites or woodworm appear, we stop work in that zone and call an independent pest specialist and a structural technician, who issue a written report and sign-offs.

Then the decision to keep, reinforce or replace goes into the quote as a separate line, not dissolved into the total. Work is done by our own crew and trusted subcontractors, with one person responsible for the site. Payment is under contract, in stages. We run projects in Russian and Spanish, so the specialists' reports and the community's decisions are read in the language you prefer. If you are choosing an old house to buy and renovate, write to us before signing the arras: we reply within an hour and discuss which points to check and how much to set aside.