The average cost of a basement renovation is € 12,000, although the price can vary between € 4,500 and € 34,000. The factors that mainly affect the budget are the total area of the basement and the type of tasks to be carried out, which will determine the need for an architectural project and the obtaining of certain construction permits.
One of the most important aspects is the state of the facilities since their non-existence or conditioning will represent a good percentage of the budget. In addition, it is convenient to attend to the need for possible waterproofing and insulation tasks and the quality of the materials to be used.
A house with a basement multiplies its potential and value, so it should always be a great advantage. However, the uses of this space can be very varied, depending on the case, so it is convenient to study its real possibilities, which are determined by the structure itself and, depending on it, to what use we want to allocate this space.
When the structure allows some flexibility, the reform can lead to an important annex to the house, even becoming its own and individualized nucleus. On the other hand, when the possibilities of action are less, its reform may mean the configuration of a storage or recreation space.
According to the aforementioned, before thinking about a definitive use, it will be necessary to review the structure to see what conditions we face. On the one hand, it will be necessary to see if the height is sufficient and if it is possible to increase it by digging. On the other hand, if there are conditions for good ventilation, lighting, and heating or sanitation facilities are required. Basements are usually colder and more humid spaces than the rest of the house, so you will have to act accordingly.
The hiring of technical personnel will be essential to determine all the aforementioned aspects and anticipate possible problems.
Before starting to carry out a basement reform, it is necessary to find out the necessary permits for the tasks that will be undertaken. Depending on the entity of the actions, the permit to be issued by the city council may be for minor or major work. In addition, there are a series of additional fees and permits if debris management or partial occupation of the road is required for the placement of structures and other related elements.
The city council will study the project to verify its scope and respect for current regulations and conduct inspections to verify its execution. Inspections are even more rigorous if you want to install a bathroom or kitchen in your basement renovation.
Most of the architecture and engineering companies or professionals that offer the comprehensive basement renovation service are in charge of carrying out the work project, if necessary, and obtaining the pertinent permits.
The cost of the reform project is usually calculated on the total price of the work, generally located between 7 and 10%. The administrative fees that must be paid are the Tax on Constructions, Installations, and Works (ICIO), whose amount is a percentage of between 2% and 6%, on the total value of the work, and the Tax for Provision of Urban Services (TPSU) or Urban License, which will be more or less high depending on the type of work and the affected area.
Depending on the structural possibilities and the existing deficiencies to be solved in the space, depending on the purpose sought, works of greater or lesser importance will be carried out. Thus, for example, a basement can be set up as a living room or recreational space, gym, cellar, bedroom, warehouse … But also as an independent home.
The magnitude of the reform
There are different ways to carry out a basement renovation, depending on your needs and goals. The most comprehensive reforms include electrical and plumbing installations and lifting walls or compartments of the space. At the same time, the simplest will focus on making the necessary finishes to beautify the space, such as preparing the walls and laying floors. In either case, waterproofing and insulation work is highly recommended.
Since basements are often below street level, water seepage and humidity problems can be recurring. Therefore, this aspect must be solved in the initial phases of the reform. To do this, it will be necessary to control the possible origin of the leaks, if they exist, or anticipate them, and review the condition of the foundations.
Depending on the permeability of the basement and its foundations, it may be necessary to protect it by installing double insulating walls, cement mortars, sprayed cork, active electro-osmosis, polyethylene drainage sheets, liquid resin injections, or sump pumps.
The average cost of a waterproofing service is € 70 / m2, although this value, depending on the system used and the size, can vary between € 15 and € 160 / m2. To cite some examples, inserting a waterproof sheet into the wall can cost around € 17 / m2, while chemical injections of silanes and siloxanes can have a starting price of € 90 / m2.
Some of the waterproofing systems can also help thermal insulation in basements. These, in general, are colder and require insulating materials that help maintain a comfortable temperature.
Of the different options, fibrous materials, such as fiberglass or mineral wool, are the least economical. LOS insulating materials such as polyurethane and expanded polystyrene are among the products sold at an average price. Finally, granulated materials from agglomerated particles are somewhat cheaper. Thus, depending on the material, the value of an insulation work can range between € 10 and € 80 / m2.
Wood and cork are materials usually used in these environments. You can also choose to install underfloor heating or carpets. This last option has an average price of € 30 / m2.
Having a good ventilation system is vital when using this part of the house. In cases where you want to install a kitchen or fireplace, you must comply with the safety regulations regarding the extraction of gases.
Thus, kitchens must have, in addition to a simple ventilation system, their own mechanical ventilation system to evacuate the vapors and odors generated by cooking food.
In basements, forced ventilation systems are used when natural ventilation does not allow the air to be kept in the proper conditions. Its installation costs, on average, about € 2,000.
When the structure allows it and the height is low, obtaining an adequate height lies in digging the ground. This operation can be carried out from € 60 / m2.
When the earth cannot be extracted, one way to disguise the low height of the space is to accentuate the verticality through furniture, with low and wide or tall but narrow furniture.
If, on the other hand, the basement has a ceiling that is too high, it may be advisable to install a false ceiling, the average price of which is estimated at € 35 / m2. False plasterboard or plasterboard ceilings are very common, given their easy handling and lightness. Moreover, the wooden ones can contribute to generating a warmer environment, although they are less economical.
The most expensive basement renovation is usually one that takes place in a vacant space. For example, if your basement only has the master pillars and the walls that delimit the space from the outside, you may need to place partition walls to create a variety of rooms, whether they are made of wood, plasterboard, or brick.
A brick or plaster laminate partition can cost between € 12 and € 40 / m2, depending on the type and thickness. The most expensive walls incorporate specific materials for functional purposes, such as fire-retardant coatings or sound insulation.
It may be interesting to include glass blocks to separate some areas or insert some dynamism in isolation on the walls and between floors. Their price varies greatly depending on their shape and color, being possible to find them from € 2 to € 45 / u.
The use of the sunlight is going to be essential since the light is scarce in the basement. If there are windows, it would be a good idea to see if they can be enlarged or new openings. In addition, installing skylight systems can be a satisfactory solution when opening openings is impossible. Another aspect to consider is installing mirrors in strategic areas to try to make the light bounce back towards the interior.
PVC practicable windows are ideal solutions for small openings, as they offer great durability, great insulating capacity, and a moderate price. Its installation price for small windows can range from € 100 to € 200.
The installation of artificial light must be carried out from very careful optics, allowing a homogeneous distribution combined with points of light. Therefore, LED lighting is currently the most sustainable lighting system.
The plumbing installation cost will depend on the number of necessary consumption points, especially if kitchens or bathrooms are installed. If the system does not have access to the basement, it will be necessary to design a plumbing installation for this area. This service may become more expensive depending on the complexity of the installation and could easily reach € 1000.
If we want the basement to have a beautiful aesthetic, the most convenient thing is an interior decoration service. This order can be contracted for a highly variable price that starts from a minimum value of € 200. A decorator will help us, for example, to choose the most suitable wall covering and its combination with the rest of the elements, according to the uses that are given to the space.
Possibly, one of the materials that are being used the most in current basement renovations is micro cement, applied to floors, walls, and other elements. Its greatest advantage is the versatility and the feeling of spaciousness it generates. The average application price of this material is estimated at € 45 / m2. Microcement can be combined well with stone cladding, the cost of which is usually around € 65 / m2, although it can vary depending on the type of stone. There are also decorative tiles made of brick or stone imitation for a price between € 20 and € 70 / m2. Its installation is faster and easier, which reduces costs, and the result is very realistic.
Another interesting resource for these rooms is artistic painting. The design and painting of a mural can be contracted for an average price of € 1500.
A basement can be the ideal place to install a living room, which can be very useful in hot climates. However, a fireplace can also be provided for use during the winter, depending on its ventilation conditions. In addition, they can be very well used spaces for social gatherings and combine their use as a cellar or constitute an appropriate place for the recreation of children and adolescents.
Furnishing this space with one or two sofas, a coffee table, a dining table, and providing the room with shelves and other auxiliary furniture can cost between € 1,500 and € 4,000.
Taking advantage of a basement as a gym can be a beneficial solution. You can insert several machines or leave a space for exercises such as yoga and Pilates, or install a sauna or Turkish bath if the ventilation system allows it.
For a standard workout, installing a folding bench with several positions, a set of dumbbells, a bar and discs, and an exercise bike can cost approximately € 350. It is also advisable to have a floor protector, marketed from € 20, which cushions impacts and reduces noise.
Converting a spacious basement into a movie theater or fitting it out for practicing with instruments can be a dream for many people. For this, it will be convenient to have good soundproofing.
Installing a bedroom in a basement would be recommended when the rest of the house has few spaces for this purpose. Furnishing a bedroom with a double bed, dresser, wardrobe, and bedside tables usually has a starting cost of € 1700.
Converting this space into a storage area is an economical option since it is unnecessary to resort to large facilities, and it will free up space on the floors. However, in this case, beyond the aesthetic component, it will be necessary to tackle possible humidity problems and condition the space with furniture or shelves suitable for the goods to be stored.
Galvanized metal shelves, which are very comfortable and resistant to store objects of all kinds, can be found at a price that ranges between € 30 and € 170, depending on the weight they can support.
Conditioning a basement as an individual home can be very interesting if enough space and its characteristics allow it. However, the reform will be significantly more expensive compared to the rest of the cases. This means having an individualized space with a bathroom and kitchen, either for one-off visits or to rent or segregate the space.
Buying or renting a home has become a luxury, so creating an apartment with the idea of separating it from the original construction can be a solution for the emancipation of children or to obtain some economic compensation through a rental scheme. However, to carry out this procedure, it is necessary to comply with current regulations, specifically the Land Law and the Horizontal Property Law, together with other regulations at a regional and local level, as well as the Technical Building Code, which incorporates the requirements minimum necessary for a home to be habitable.
Building a bathroom in a basement is more complex than building on overhead construction, as special plumbing is required to ensure that the drain is connected to the sewer. In addition, there is a possibility that the sewer is not deep enough to allow the basement bathroom to use gravity in the same way as above-ground toilets.
Therefore, in basement renovation, installing a toilet can be very expensive because it is likely that you will need to invest in an appliance that, instead of using gravity, uses a mash function that disintegrates the waste to avoid clogging or incorporating an evacuation pump. The price of this artifact ranges between € 100 and € 400.
Openings leading to basements can be very accessible to intruders. A solution could be to install bars, which can be found from € 80. However, this can harm the luminosity, so it is recommended to use hinged windows with interior locks that allow them to be blocked, armored glass, or an alarm system.