How to remove ceilings drywall

Secure connection between wall and ceiling without cracks

For a long time, surface qualities for filling work on plasterboard surfaces have been precisely defined in leaflet No. 2 of the Federal Association of the Gypsum Industry in order to protect and strengthen specialist contractors. But what use is the best surface if the wall and ceiling connections tear off a few weeks after installation. Because who does not know the unsightly detailed images that you often see in corner and connecting areas between walls and ceilings or sloping ceilings. Therefore, joints and connections must be carried out properly according to the current state of the art.

Basic requirements for joints and connections

Before going into detail and starting to carry out the work, you should always be aware of certain basic requirements. Because joints and connections must always be planned and carried out in accordance with the following principles:

Plasterboard surfaces must be structurally decoupled from other components (for example from wood or concrete components).
Suspended plasterboard ceilings must be structurally separated from integrating supports and built-in parts (such as ceiling lights).
If movements are to be expected in the shell (e.g. variable traffic loads, subsidence, etc.), sliding wall and ceiling connections must be made.
In the case of pronounced changes in the cross-section of the plasterboard surfaces (for example, hallway bulges or re-entrant walls), joints must be built in.
A sufficiently long and moderate drying and heating phase must be planned in order to avoid a very rapid drop in relative humidity.

Joints and component connections in the interior

Experience has shown that there are particularly critical areas at component connections and in the attic. Here the craftsman must pay particular attention to correct execution. In practice, connections between a wall covered with plasterboard and a wooden ceiling are often made with an acrylic joint. However, one must consider that with such a component connection there are two completely different components. If there are fluctuations in humidity, they move to different degrees and in different directions.

In practice, this effect is often visible through the formation of cracks in the connection area if the room air is relatively humid at the time the components are installed (for example due to residual moisture escaping from concrete foundations or screed) and then (for example, when the underfloor heating is started up) is heated up significantly within a few hours . The relative humidity drops sharply within a very short time, which leads to the shrinkage of the various components. Since, for example, wooden components shrink ten times more than plasterboard, such high shear forces occur in the area of ​​the connection.

The DIN allows such connection joints to be made with acrylic, but it is essential to ensure that the acrylic compound adheres to two opposite flanks of the joint and can stretch sufficiently. Assuming that an acrylic mass can expand by about 20 percent when pulled, the joint would have to be about 5 to 8 mm wide when the components move by 1 to 1.5 mm. With a standard board thickness of 12.5 mm, a relatively large amount of acrylic mass would be required.

Usually, however, an acrylic joint on the construction site is not executed as required by DIN. Gypsum boards are often mounted flush with each other or flush with wooden components in the connection area. The material thickness of the subsequently applied acrylic mass is inevitably too small to be able to stretch accordingly at all. In addition, with this type of processing, the acrylic adheres to two touching flanks, which means that the acrylic is simply sheared off with small movements.

But even with correctly executed acrylic joints, it is important to remember that the joint is usually painted over. Usual colors (for example emulsion paints) form a rigid film on the plasto-elastic acrylic material after they have dried out. If there is a difference in humidity, the length of the adjacent components changes. The acrylic mass is stretched or compressed, which then leads to flaking and tearing of the immovable and rigid layer of paint on it. That looks ugly and is usually claimed by the customer as a crack.

Separation strips - the safe solution

This crack problem can be avoided by separating adjacent components. In addition to the freely movable ceiling construction via a shadow gap, which is particularly recommended for larger ceiling areas, the installation of a separating strip such as "Knauf Trenn-Fix" is a safe solution. The separating strip consists of a thin, 65 mm wide Silicon paper with a 1 cm wide adhesive strip on one side. No filler adheres to the separating strip. In addition, a few special adhesive dots are applied to the rest of the surface, which enable it to adhere to the substrate while at the same time being easy and residue-free to remove. As a result, the separating strip can be attached in a dimensionally stable manner without the well-known wave formation in the component connection, even with very high building site moisture.

"Trenn-Fix" is stuck with the adhesive strip directly next to the profile on the adjoining component so that the weakly adhesive area protrudes to the side. The plasterboards are then, as is customary with separating strips, installed at a distance of about 3 to 5 mm from the strip and then leveled with joint filler. After the filler has dried out, the protruding separating strip is cut off. With the adhesive strip (gypsum board thickness), which is only about 1 cm wide, and the few additional adhesive dots, you can easily remove the cut-off remnants of the strip. In this way, a permanently functional sliding ceiling connection is created, which does not appear as a jumping "jagged" crack, but as a mostly imperceptible clean hairline similar to a shadow groove. This means that even permanent movement of the components with respect to one another is possible without cracking.

Joints in the attic

The connections in the attic extension between the pitched roof paneling and the solidly built gable or partition walls should be carried out in the same way. The airtightness required there must be ensured with the properly implemented vapor barrier below. The transitions from the jamb to the sloping roof should be firmly connected. In addition to stabilizing and fixing the transitions by backing them with a flexible corner profile (such as "Knauf Flexible Corner Profile"), the joints should be filled with a high-strength filler (such as "Knauf Uniflott") and with a foldable, high-strength joint tape (such as "Knauf Kurt") become.

Author

Petra Stöcklein is team leader drywall market management at Knauf Gips KG in Iphofen.

From Petra Stöcklein