Inventory of the framwork
Anyone who buys a half-timbered house will sooner or later have to carry out certain renovation measures on the building.
When planning a building project, one should take a look at the overall condition and get a proper, thorough picture of the general state of the house: What materials were used? What is the insulation condition? What is the most urgent work?
To take stock of the situation, it is initially sufficient to walk through the house and around the outside with watchful eyes. Weak points, which typically show damage, move into the focus of attention. Indicators of damage to the half-timbered house are moisture in places where it does not belong (actually affects every place that has nothing to do with a water supply and drainage), wood damage such as loose parts of the framework and unsuitable building materials.
Inner values
If you find exceptionally smooth walls on the inside of the half-timbered house, you should check the material of this wall.The use of gypsum in half-timbered houses often results in moisture damage, as gypsum stores moisture for quite a long time, but does not release it again. Half-timbered beams plastered with plaster containing gypsum are therefore above average damp and often show signs of damage. Nailed-on gypsum boards, in turn, creates cavities in which the moisture from the room air condenses. In the lower area of ceiling joist supports or sill joists, this also causes moisture damage.
Cement, whether used as plaster or for brickwork, for example in the form of pumice stones, is too hard and too solid a building material to be in the right place in the compartments: on the one hand, it causes the compartment and joists to tear, which in turn allows more water to penetrate, and on the other hand, cement does not absorb moisture. Consequently, the wood has to absorb all moisture and transport it further (moisture from the inside from the room air and from the outside, which acts on the building as driving rain). The wood alone cannot manage this, which is why the combination of wood and clay is optimal, as these two building materials effectively protect the half-timbered house: The wood remains permanently dry because the clay removes the moisture from it.
Literature about that topic
Insulation on beams
Mineral insulation materials such as glass or rock wool or synthetic insulation boards made of petroleum-containing foam in the interior of the half-timbered house often cause mold and moisture damage in the area of the exterior walls. Anyone who finds such insulation materials should urgently examine the condition of the walls behind the insulation. Sometimes it is easy to identify the building material used, for example by removing a light switch or socket and looking into the hole. Otherwise it is possible to inspect the material at hidden places.
Ceiling beams deform over the decades (or centuries) and sag to a certain extent. This is normal and doesn't have to be harmful.
Former wood connections are often visible through drill holes or mortises. If you find several such holes in a beam or in a wall level, this indicates an earlier conversion. These points should be checked for their statics and stability.
Outer facade
Outside, it makes sense to examine the strength of the house and thus determine its stability. Indicators of possible damage to the framework are acrylic paints, varnishes or other sealing paints used.
Critical points that deserve special attention are the lower window connections, especially of windows that were installed with the help of construction foam, the threshold areas and the points of intersection between threshold and stem and the plastering of the compartments.
The plaster must be free of cracks, it must not allow driving rain to penetrate the framework, and the material must harmonize with a half-timbered house: lit cement-based plaster is too hard because moisture penetrates through the cracks that occur, but does not evaporate out again and thus damage the wall can.