Laying a vapor barrier: how far does the vapor barrier have to go?

Vapor barrier and vapor barrier are important elements in the construction or expansion of rooms. You can find out how far they are to be moved here.

Vapor barrier or vapor barrier?

Although the terms are often used interchangeably, they are different materials. A vapor barrier is used when the sd value is between 0.6 and 1,500 meters. The vapor barrier is used from 1,500 meters.

The sd value stands for "water vapor diffusion equivalent air layer thickness" and indicates the resistance of the material to water vapour.
Before laying, it must therefore be clear what value is given in order to make the right decision.

function

Whether lock or brake: It is a material that prevents the penetration of water vapor or humidity into the insulation of the walls. It should therefore be installed in every room that is exposed to increased humidity. This includes:

• bath
• Roof
• Kitchen
• laundry room

This can also include rooms with a large number of leafy plants, indoor fountains or aquariums. The roof should definitely be equipped with it, since warm and therefore potentially more humid air rises and spreads there in the building fabric. The possible consequences of this are:

• Building materials rot
• rot
• Mold

On the one hand, this can result in substances that are hazardous to health and spread through the room air. On the other hand, the building fabric suffers. This can generate high costs and also entail immense effort.

Possible materials

Various materials can be used for the locks and brakes. These include, for example:

• aluminum
• Plastics such as polyethylene or PVC
• OSB3 and OSB4
• Paper

Often these are foils, but plates can also be used in the case of aluminum and OSB. Both variants have advantages and disadvantages.

foil

The advantages of film vapor barriers are:

• easy cropping
• lower weight
• easier attachment

Another advantage is that the film can be attached more flexibly. In the case of difficult sloping roofs, bay windows or other special structural features, this makes work easier and can significantly reduce the effort. The disadvantage, however, is that foils can be damaged more quickly than plates and may therefore have to be replaced more frequently.

plates

Fixed plates have the following advantages:

• provides a good base for attaching the cladding
• durable
• stable

However, they are heavier and less flexible when it comes to attachment. Cropping is also more difficult.

Laying foil

In order to create an effective barrier against steam and humidity, a number of factors must be taken into account when installing. But first you need the right tools. These are:

• scribing pen
• cutter knife
• foil
• staples if necessary
• duct tape
• Glue
• Measuring tools, such as ruler and scaled square
• spatula

Once the equipment is ready, the following steps are required:

1. cleaning

The surface is swept before laying. It should be smooth and swept clean.

2. Lay out the foil

The foil is unrolled so that it extends from one rafter to the next and overhangs both walls and rafters.

3. Measure and cut

The vapor barrier should protrude by at least two centimeters on walls. It even has to be ten centimeters on the rafters. Also take into account any cut-outs that may be necessary, such as for load-bearing beams.

4. lay out

After cutting, the film is laid out and aligned again. It should also be smoothed out well with the spatula.

5. Fasten

You can staple the vapor barriers to the rafters at regular intervals. On the other hand, they are glued to walls and other vertical surfaces. To do this, fold two centimeters of the edge upwards as a fold. The adhesive is applied between the wall and the foil and smoothed out with a spatula. There should be no air bubbles underneath.

seams

The vapor barrier seams must overlap each other by four inches. They also have to be glued together. However, only adhesive tape is required for this. Be sure to seal the edges tightly and evenly.

lay plates

If you are laying slabs, the process is similar. After measuring, cut them accordingly. In contrast to the film, however, a saw and not a cutter knife is required for this. They can also be bolted to the rafters to provide more stability.

Put

In the case of panels as a vapor barrier, overlapping of the individual elements is of course not possible. Otherwise unevenness would occur. They must therefore be aligned in such a way that the resulting gaps are as small as possible.

In addition, it is necessary to glue the joints between the panels and the gaps to the walls. Otherwise, water vapor could still penetrate the insulation. Parquet floor adhesives and assembly adhesives are suitable for this.

Learn more about roof / attic