Bitumen sheeting: this is how you lay a welding sheeting on concrete

With the right instructions, a bitumen welding line can be laid comparatively easily on concrete. The material is very cheap, seals well and has a long service life. When attaching, however, some basic requirements must be observed. We offer the relevant knowledge through tips and instructions.

Bitumen sheeting: advantages and disadvantages

The decisive advantage of the bitumen sheeting compared to self-adhesive or cold-adhesive bitumen sheeting is the price - the material is significantly cheaper. In addition, the hot gluing or welding ensures a high level of tightness. As a result, bitumen sheeting can also be suitable for laying on flat roofs, from which rainwater cannot drain off too quickly.

disadvantage

A possible disadvantage, however, is that the bitumen welding sheets have to be attached using a gas burner. They are therefore not suitable for laying on wooden roofs or other combustible materials, as the burner can cause a fire. However, this problem can be avoided by using an intermediate length or a cold-bonded bitumen layer. In addition, there is no danger with a concrete base anyway.

difference

Another crucial difference between cold-glued and welded bitumen sheets is the effort involved in attaching them. Self-adhesive sheets can be rolled out and attached after the roof has been prepared. All that is required is to pull off a film. In the case of the cold-adhesive strips, an adhesive bed is applied and the strips that have been cut to size are aligned and pressed into place.
Tip: In the hot process, seams and entire strips have to be processed with the gas burner. As a result, the effort is significantly higher.

preparation

Before laying the welding line, a few preparatory steps must be taken. These include:

1. The roof needs to be cleaned thoroughly. Soiling can reduce the adhesive strength of the membrane. In addition, pointed pebbles or other sharp or pointed objects can drill through the bitumen sheet from the inside and thus cause the roof to leak.

2. Before installation, the roof must be dry and free of grease. In wet weather, you should therefore refrain from laying the sheets. Alternatively, the concrete surface can be carefully dried with the gas burner.

3. The bitumen sheets are cut to size. Ten centimeters are planned as an overhang at the roof edges and around eight centimeters as an overlap between the strips. Sharp and strong scissors or a cutter knife with a hooked blade are suitable as cutting tools.

4. So that the rolls or sheets can be laid out, they will be spread out on the roof for a few hours. If the sun is shining very strongly, the bitumen sheeting should already be correctly aligned, as the adhesive could heat up and adhere.

Note: The bitumen rolls should never be stored lying down. Heat can liquefy the adhesive and the strips stick to one another or stick to themselves. It is therefore better to position the patient standing up. Even here, however, the individual roles should not be too close to one another.

Instructions for laying - step by step

Once the preparations have been completed, the sheets can be laid. The following sequence must be observed:

1. The sheets are laid from bottom to top. So it starts at the bottom of the roof. If the roof has no slope, start on the leeward side.

2. The first sheet is placed, aligned and weighted - so that it cannot slip during welding. It should protrude ten centimeters on each side of the roof.

3. The edges of the web are heated with the gas burner. The heat melts the material and sticks to the substrate, i.e. to the concrete.

4. The bitumen sealing membrane can be pressed on with a broom and glued on without creasing. Since the broom can no longer be used afterwards, either an old broom or a cheaper one should be used.

5. The second bitumen sheet is laid in such a way that the edge overlaps the first sheet by about eight centimeters. Again, the edges are heated with the gas burner and pressed down with the broom and smoothed out.

6. Step 5 is repeated until the entire roof is covered.

7. Afterwards, the individual strips can be evenly heated completely again with the gas burner and smoothed out with slight pressure. This step is not necessary if a second bitumen layer is to be applied.

After the first bitumen layer is ready, the protruding bitumen edges are also glued to the roof edges with a gas burner and broom. For a particularly long service life and a high level of impermeability, it can make sense to apply a second layer of welding strips. If you want to lay the material in two layers, you do not have to heat the first layer throughout. It is sufficient to just weld the seams. In the case of the second layer, the material is then continuously heated and smoothed to create a tightly sealed layer.
Tip: With the gas burner, it is worthwhile to compare rental and purchase prices. The rental fees are sometimes very high. This is especially true if the device is needed for several days. Therefore, buying a simple gas burner can actually be cheaper than borrowing it from a hardware store.

Caution: risk of fire

When processing the bitumen sheeting, there is a risk of fire and injury due to the use of a gas burner. Therefore, the following three safety precautions should be taken into account:

1. Fireproof roofs only

The above instructions are aimed solely at laying welding tracks on concrete roofs. If it is wood or other combustible materials, either self-adhesive bitumen sheeting or bitumen sheeting for cold bonding should be used - at least for the first layer. Even then, great care should be taken when welding the second layer and work should be done with brisk movements so that the roof is not overheated in certain points and goes up in flames.

2. Protective clothing and devices

Protective gloves and appropriate work shoes are just as much a part of handling the gas burner as a fire extinguisher is within easy reach. To be on the safe side, the sheets should not be laid and welded alone, so that an assistant can intervene when the fire is extinguished. Anyone who feels that this is overly cautious should bear in mind that even with experts, roofs can catch fire due to unfavorable conditions.

3. Swift work and controls

To avoid excessive heating of the bitumen sheeting, the gas burner should be guided over the material with swift and even movements. A stick or stick can then be used to check whether the edges of the bitumen sheet are already soft enough to bond with the substrate and the following sheet. Usually the control only has to be carried out on the first few lanes, after which a feeling for how quickly develops or how slowly the gas burner has to be guided over the seams and strips in order to achieve the right consistency obtain.