Scarfing
As Scarfing refers to the heating of the bottom and welding of roofing felt or bituminous welding paths for the permanent connection and the homogeneous fusion of the butt joints of several welding or sealing web layers, and the subsequent correction of leaks, as used in the sealing of a roof construction or the horizontal and vertical sealing of the foundation is necessary. Flaming is carried out using a propane gas burner . The advantage of this process is that no additional adhesive bitumen is required and work progresses quickly.
Use in construction
Scarfing is used in the construction sector for sealing flat roofs , balconies , terraces or for sealing against pressing water in the foundation area, such as the black tub . Sealing by scarfing is also necessary when building a green roof .
Working on a warm wooden roof construction regularly involves a high risk, as the roof structure can catch fire if the gas flame is improperly used. This is what happened, for example, during reconstruction work in Vienna's Sofiensaal , which burned down to the load-bearing masonry in 2001 due to improper scarfing work.
Alternatives
For the production of a black tank and also in the roof area, the cold self-adhesive process with cold self-adhesive bitumen sealing membranes was developed, which require a shorter processing time and are also used in hazardous areas as a fire protection-safe variant. The special strips are glued to the substrate or to each other by removing the peel-off film on the underside, which makes the use of an additional hot-melt adhesive or the burner unnecessary. The material is, however, more expensive than the conventionally flame-welded sheets.
The oldest method, which is only used by a few roofing companies and which enables void -free bonding, is the so-called pouring and rolling method . Here, a hot bitumen is poured from a can in front of the sealing membrane to be glued in such a way that a bitumen bead runs in front of the roll over the entire width of the membrane when the membrane rolls into the hot bitumen. Lanes with a sanded underside ensure particularly good bonding. Since this method does not use a flame on the roof, the subsurface has to be dry, which means that such installation is only possible when the weather is appropriate.
In the so-called brush coating process, liquid bitumen (oxidation bitumen or polymer bitumen) is applied so abundantly with a brush in front of the rolled-up roofing membrane or roofing felt that an adhesive bead is also formed here when the membrane is unrolled in front of the roll. However, this method has not been used for many years due to the enormous effort involved.
Occasionally, loosely laid seals made of plastic sheets with mechanical fastening or under load are also used.
Hot air welding is a modern but also very cost-intensive alternative . This is a seam-joining technique for plastic sheets in which the at least 5 cm overlapping plastic sheets are thermally softened without the addition of foreign substances, i.e. only with hot air and immediately joined under pressure. Welding temperatures of 450 to 500 ° Celsius and a contact pressure of 5 to 6 kp are required here. Since the welding speed has to be adjusted to the contact pressure of the respective plastic sheets, test welds are carried out. The essential factors for the weldability by hot air welding are above all the material quality, the technical equipment, the type of plastic sheet used, the substrate as well as the ambient temperature, the moisture content and the degree of aging of the sheets to be welded. The work is carried out with a special automatic welding machine.
Similar procedures
- Thermal weed control by flaming in agriculture and horticulture
- Flaming in food production
- Removing udder hair from cows using udder hair remover
- Gassing in textile finishing
- Flame blasting in concrete repairs
See also
literature
- Frank Frössel: Lexicon of building sealing and cellar renovation, Baulino Verlag 2005, 1st edition 2005, ISBN 978-3-93853-705-3
- vdd Industrieverband Bitumen-Dach- und Dichtungsbahnen eV (Hrsg.): Technical rules for the planning and execution of seals with polymer bitumen and bitumen sheeting . abc of the bitumen sheeting. 3. Edition. vdd Industrieverband Bitumen-Dach- und Dichtungsbahnen eV, Frankfurt / Main 2008, ISBN 978-3-9801831-8-5 ( PDF, 3.8 MB [accessed on July 29, 2010]).