Shrinkage cracks - allowable width

Concrete in the attic? I think there is a misunderstanding! If you have a good relationship with the construction company, just ask which shrinkage cracks are meant. I guess it’s the joint between the drywall ceiling and the exterior masonry. That will only become stable very late, and any acrylic joints applied during construction will reopen. However, that is something completely different from the quality / crack class of a [WU Beton] basement! If this is defined too vaguely in the specifications, I would recommend simply changing it, and if that is not possible there, I would include it as an additional agreement in the contract.

Hello house seller,

You are absolutely right. Sometimes you sit in front of it and can't see the forest for the trees.

Of course, the attic has a wooden beam ceiling.
The ceiling of the ground floor will be "a reinforced concrete ceiling according to static requirements as a system ceiling with a cast-in-place concrete layer."
The walls will be made of Ytong blocks.

Regardless of that, the question remains as to which shrinkage cracks are permissible.


Do the shrinkage crack dimensions you posted also apply to other materials or are, for example, Ytong blocks also susceptible to shrinkage cracks.
Somehow, I can't get a grasp on this topic.

Shrinkage cracks can always occur when the material changes (contracts) due to the drying progress. This is normal.
If a damp plaster surface is connected to a drywall panel, a small gap forms. However, the plaster surface continues to dry out and changes its dimension. The gap becomes larger. If I had previously inserted something into this gap, it no longer fills the gap completely. A shrinkage crack has formed. Whether this crack is 2 or 3 mm wide is actually a minor issue. It simply needs to be resealed. Ask around among acquaintances, people who have built stone on stone and have already lived in the house for a year.

You will hardly find a construction company that gives you a warranty on this gap/joint because it will always open up. All promises that this will not happen and all the immaculate constructions that are supposed to prevent this are worthless. Many drywall installers have sworn to me that they always build in a way that the joint does not open. Nobody has succeeded yet. The simplest solution is a trowel cut in the plaster to keep the joint open. This should then be sealed very late (painting work) with acrylic. The joint that later opens again can then simply be permanently sealed with acrylic.
Please also pay attention to the joint connections of the floor coverings. The screed will also change during drying out and the baseboards will have to be reworked later. Of course, you can agree for a corresponding fee that the construction company closes all joints and modifies the baseboards again after a defined period. There will certainly be no warranty for this either. However, you save yourself the trouble of doing it yourself.

There are also permissible widths for shrinkage cracks in plaster or masonry. If you want to discuss all this with the building partner and try to change the contracts because of it, it will become very complicated and your building partner will become very suspicious. The consequence may be that he decides against the contract because he certainly does not want to spend his time on "endless debates about possibly occurring cracks and their permissible width."
It is best to require your building partner to build your house according to the recognized rules of technology and the respective valid DIN standards. In the event of damage, it is then clearly defined what is a defect and what is not. You can rely on that and, if necessary, also argue about it. Furthermore, the roof truss should be made of structural solid wood (KVH) and the lathing of the gypsum board ceiling should be made of aluminum profiles. (This should actually be in every contract)

I forgot to mention that cracks in the aerated concrete block are not allowed! This material must be processed crack-free. Otherwise, there will be major issues with the structural integrity!

Hello,

Of course, the attic has a wooden beam ceiling.
The ceiling of the ground floor will be "a reinforced concrete ceiling according to static requirements as a system ceiling with an in-situ concrete layer." The walls will be made of Ytong blocks.

So, not a "modern" construction in the sense of the Brussels planners after all; I was already wondering. There have long been single-family houses that are made entirely of concrete; accordingly also in the attic. These do not necessarily come across as a "squeaky house" either.

Do the shrinkage crack measurements you posted also apply to other materials, or are, for example, Ytong blocks also prone to shrinkage cracks?

If significant cracks occur when using aerated concrete, Poroton, or also sand-lime bricks, errors were already made in the foundation of the construction project. There can be load-dependent as well as load-independent causes; explaining all of this would not help you further, as it can only be described very technically. Search the web under xxx.DIN-Bauportal.de/Index.php?mid=121; here you will find a – in my opinion – layman-friendly explanation of how cracks in masonry occur and why.

Somehow I can’t get to grips with this topic.

Your question shows that you talk too much with the person from the Builders’ Protection Association. In the end, exactly what I don’t appreciate about their offers happens. You as the builder are more unsettled than enlightened, and on top of that, you pay for it.

**The causes leading to the formation of cracks in ceilings and walls are very complex. Often, cracks in conventional building materials are not entirely avoidable. Therefore, the mere fact of a visible crack in a component does not in principle allow the conclusion that there is a defect or damage has occurred. Generally, a completely crack-free surface cannot be produced or only to a limited extent. This applies particularly to mineral exterior renders. The plaster standard (DIN 18550-2) therefore states that "isolated hairline cracks" (definition: crack width < 0.2 mm) are not to be criticized, as they do not impair the technical value of the plaster. The decisive criterion in the question of whether cracks in the plaster are acceptable is thus not the mere presence of cracks but rather the consequences of the cracks for the required optical and technical functions of the plaster.

**Source: Gänssmantel, publicly sworn & appointed expert

As the user "Hausverkäufer" correctly wrote, your contractor will hardly agree to a verification in the contract. This is also not necessary as long as the following sentence is recorded in the BB or as an addition to the contract: "the contractor undertakes to execute the construction project according to the currently valid rules of technology." This still does not protect your construction project from cracks – it cannot – but it obliges your contractor to repair cracks >0.2 mm.

Fundamentally, earlier contractors were right when they said that a new building needs its time, a shell should stand quietly for a while before interior trades begin. Nowadays, and with the demands of many builders to be in the house as soon as "yesterday" after signing the contract, this has brought planning stones into play and thereby other reactions => the material always wants to avoid stress through movement. If this movement is not possible (how could it be?), an obstruction occurs and the external forces (loads) build up stresses within the material. This causes cracks which – as the DIN states – are allowed within narrow tolerances, as they cannot be prevented.

Rhenish greetings

Hello construction expert.

Where has the link to the PDF of [Gänssmantel] actually gone? Are you not allowed to insert links in this forum?

Greetings from Berlin