How do you build a room dry

Expand the basement and gain space in the basement

At some point you get tired of the junk rooms in the basement. I want order. Needs space. Would like to build in comfort. Go for it: You need to know that if you want to expand, convert and re-use the basement and thus upgrade the basement.

The living space is becoming scarcer and more expensive, so why not expand the basement? And so create space for the study or children's room, the long-desired sauna? Maybe even a granny flat can be rented out.

First things first - be sure to think about planning permission. A change of use is required if the classic cellar is converted into living space. If you build without it and the building authorities find out about it, it will be expensive.

In order to get a permit, you have to pay particular attention to the floor area number (GFZ). This number regulates the maximum number of square meters of floor space (external dimensions of the building) that are permitted on the property. Example: GFZ 0.7 for a property size of 600 m 2 means that you may have a maximum of 420 m 2 of floor space.

If you have already used your property to capacity, the GFZ could become a problem. Each federal state has its own state building code. This specifies how high the clear room height and how big the windows must be. The requirements for fire protection are also changing. A second escape route must be available, in most cases an external cellar staircase. And the utility cellar must be separated from the living area with an F 90 fire protection wall (offers 90 minutes of fire resistance) and a fire protection door.

Submit a building application for the cellar extension

In order to be able to submit the building application, you need a planner who can submit it to the building authority. At the same time, an architect will help you with a clever room and lighting concept. The planner creates the drawings for the craftsmen and makes an invitation to tender for the work to be done. He also coordinates the trades on the construction site and ensures that the conversions run smoothly.

The craftsmen should also be considered. The order books of the individual trades are currently well filled, making spontaneous, short-term expansion almost impossible. Plan for the long term and ask all craftsmen in good time so that there are no delays on the construction site.

Heating, water and electricity in the expansion of the cellar

If the sewer system is above the deepest drain in the basement, you must install a waste water lifting system. This pumps the water over the backflow level and also prevents the wastewater from flowing back and flooding your basement.

Install their own water meter for a tenant in order to calculate the amount actually consumed. The granny flat must also be equipped with a separate power circuit and fuse box by the energy supplier.

In most cases there are no radiators in the basement, but fortunately the existing heating usually creates the additional output easily. Since the clear room height often does not allow for an installation height for underfloor heating and screed, classic radiators are ideal - or possibly wall heating.

Remember that on an uninsulated floor slab, the basement will remain cold to the feet. You should also insulate the ceiling on the ground floor so that the footfall sound in the basement remains within the tolerance range.

There is a tendency for the air in the basement to be even more, and opening the windows does not always make sense, but rather does harm. A controlled ventilation, tailored to the behavior of the residents, improves the room climate enormously and ensures that mold has no chance.

Ventilate the basement better in winter than in summer

The basement is ventilated the other way around than expected. Because the lack of knowledge of the layman often causes moisture damage, especially when it comes to basement ventilation. That's why the rule is: Not in summer. If you want to ventilate the musty cellar with fresh air in summer, you should get damp walls instead. This is due to the so-called refrigerator effect: if we take a well-chilled bottle out of the refrigerator in summer, water droplets immediately deposit on the surface. Because warm air stores a lot of moisture - and when it hits a cold surface (for example a bottle), condensation automatically forms. This is exactly what happens when we ventilate the cellar on hot days: The humidity in the warm air is reflected on the cold cellar walls. Instead of fresh air, we pump moisture (and mold) into the basement.

So: keep windows in the basement closed on humid summer days and rather ventilate in winter. If there are living spaces in the basement and you also wash, dry and iron in the basement, ventilate early in the morning when the air is still cool. The most effective way to transport existing humidity out of the basement is to heat it up for several hours in winter (the heat draws the moisture out of the wall) and then let in icy (as dry) air. A hygrometer helps you to keep an eye on everything.

Choice of material for the expansion of the cellar

If the rooms in the basement are used for living, you should energetically upgrade the outer walls with insulation panels. These must meet two requirements: be capillary-active and non-flammable. Calcium silicate boards or capillary-active mineral foam boards provide permanent protection against moisture and prevent the formation of mold.

Otherwise a real all-purpose solution, plasterboard has no place in the expansion of the basement. There is too great a risk that the panels will soak up the moisture and thus create a breeding ground for mold.

Sealing slurry is a liquid cement-plastic mixture that is applied with a brush, usually in two layers. It is used to seal surfaces against ingress of water. The sludge should dry out very slowly.

Renovation plaster is a particularly open-pored plaster that enlarges the drying surface and allows the wall to dry out more quickly. In addition, it binds dissolved salts so that they cannot penetrate the wall surface.

Only plaster that does not contain gypsum should be used to finish the basement wall. Because plaster of paris absorbs water and swells. The color used It should be permeable, so it should be able to "breathe". You should therefore paint basement walls with a silicate or lime paint.

Seal and dry the basement

Many cellars in the old building are more like a wetland. The basement wall and floor slab are exposed to more severe conditions and, in addition to the general moisture in the ground, have to withstand pressing and high groundwater. In many older buildings there is a need for action to make the cellars usable as storage space and, above all, as living space. Various options are available for sealing the basement:

The most sensible and best method to keep the damp wall permanently dry. Unfortunately also the most complex, expensive and not possible method for all buildings. The basement walls must be completely exposed, i.e. excavated down to the foundation base. A circumferential drainage should be laid here in order to drain back water. In addition to the usual bituminous or mineral waterproofing (in combination with perimeter insulation), you can also use a method used by the ancient Romans - a clay-clay mixture that does not allow water to penetrate.

A horizontal layer injected below the cellar ceiling prevents the capillary rising of moisture into the masonry. This form of waterproofing is strongly recommended to protect the walls.

In this process, an acrylic gel or a resin is introduced into the wall or into the adjacent soil via drill holes - it hardens and completely seals the substance of the masonry.

If it is impossible to protect the house from the ingress of water from the outside, a multi-layer system is applied to the inner wall and floor. The moisture remains in the outer wall. The seal prevents moisture from penetrating the new surface. This does not solve the problem of the damp wall - but it helps to get the problem under control and to be able to use the basement fully - and the basement shines in new splendor.