MANUAL

Single-layer membranes

The most simple vapour-permeable membrane used in construction industry is single-layer vapour-permeable fibre. This fibre is extremely vapour-permeable, has wind-insulation factors and low resistance to water penetration. Due to its properties it is suitable for use in building industry only as wind-insulation provided that it is resistant to UV. The application of this material as an initial roofing is a serious mistake – such fibre cannot ensure protection against water. Even small quantities of water will quickly penetrate the fibre and dampen everything that is beneath it. Only after covering of the fibre with special impregnate the resistance to water will be improved. At the same time this fibre will ensure vapour-permeability. The drawback of such solution is the low quality of impregnate coating – when folding the fibre, the impregnate coating cracks what results in damaging of water-proof layer and consequently the fibre will not meet fundamental requirement in case of materials for initial roofing – water-tightness. Moreover, the impregnating coating is relatively thin what results in low resistance to ageing processes.

Two-layer membranes

Application of special water-proof coating (called functional film) ensures that the vapour-permeable fibre is resistant to column of water. It is a special coating that guarantees high vapour-permeability and simultaneously improves the resistance to column of water. Such membranes were quite a popular solution for initial roofing mainly due to their relatively low price. However, because of incidents of functional film mechanical damage, it was decided to protect it with additional fibre layer. The production of two-layer membranes was ceased (with few exceptions) and the common standard become three-layer membranes.

Three-layer membranes

Nowadays it is the most popular solution in membranes based on vapour-permeable fibres. They are structured of three layers – fibre layer, functional film and a layer that functions as a protection for film. Delicate and sensitive film (that has a fibre layer as a protection) guarantees resistance to tearing that can be caused due to the friction of membrane bottom part and the surface of rafters or boarding (which may be rough and uneven). The production of three-layer membrane involves joining of separate fibre layers with functional film. It is commonly described as lamination.

The most common lamination types are: thermo-bonding, ultrasonic and thermal gluing where the active joining element is glue. Application of any technology mentioned above, requires knowledge, experience and suitable machines and equipment.

The least advanced technology is joining of separate layers with glue. It should be noticed that in order to receive laminate which is durable and of high technical parameters, high quality glue shall be used what influences the membrane final price. Lower price may result from use of low quality glue or cheap technology (two-layer). Thermo-bonding and ultrasonic technologies are distinguished for their advancement and the necessity of special machines use (often expensive ones). Appropriate level of know-how and experience enable the production of highest quality membranes. It should be noticed that the lack of suitable technology base or lack of information may result in the low quality of products – such situations take place when the production lines are bought without suitable service and base (that is a team supervised by an experienced technologist). In the market one can find roof membranes of low quality that delaminate before their installation on roof. Such incidents may occur not only in case of improper service of ultrasonic technology but also in thermo-bonging technology service. Fortunately defective product can be easily verified by delamination test.