Sealing methods

Unlike a pitched roof, the roof waterproofing of the flat roof is not only used to drain rain, but must also be completely waterproof to prevent ingress of water. Which sealing methods you can apply, and what special forms there are, read in this post.

Fundamentals of the seal

The waterproofing of the flat roof always depends on the existing roof pitch. Depending on the defined roof pitch group (in DIN), a flat roof can be assigned to either Group I or Group II.

Flat roofs with inclinations up to 3° fall thereby in group I, flat roofs with inclinations between 3° and 5° fall into group II. Flat roofs with higher inclination are not considered separately in the DIN, but the respective technical rules apply mutatis mutandis, partly with necessary Additions.

Take into account the weather

The amount of rainfall is not the same in all areas. Therefore, the weather must also be taken into account in the flat roof waterproofing:

  • temperatures
  • Rainfall
  • amount of snow

In turn, the snow load plays a role for the roof construction itself.

water resistance

The roof seal must always be completely waterproof. When using webs (as in most cases) it is necessary to ensure that the seams between the webs are permanently and watertightly welded together.

Attaching and fixing the seal

Apart from a few special forms, there are several possible ways of fastening:

  • they can be glued over the entire surface
  • they can be welded together
  • they may be partially glued (eg at the joints)
  • they can be mechanically fastened (rarely)
  • they can be held by a so-called surcharge (such as gravel, usually only in green roofs)

Special forms of sealing

In addition to the usual bituminous seals (with bituminous membranes) or seals with EPDM film, a flat roof can also be sealed with other methods.

concrete sealing

A seal with WU concrete (impermeable concrete, not to be confused with the underwater concrete) is rarely performed. It is a completely watertight reinforced concrete.

Even though the technology is so far only limited and mostly limited to commercial buildings, it offers some significant advantages. On the one hand, there is a much higher level of sustainability, lower remediation costs than with the sealing with membranes (higher durability) and significantly higher safety.

For building owners, a WU concrete seal on a flat roof is therefore worth considering. There are also specialist companies that specialize in this type of roofing, and have years of experience with it. A construction supervisory approval of the method has been in place for many years.

Sealing with clay

In a clay building - especially in ecological buildings - offers as a flat roof and a sealing of the roof with clay. High rainfall is usually problematic for the clay roof, but can also be achieved in many cases with some adjustments. However, construction methods that have been tested to a large extent do not yet exist.

Video Board: 2. METHODS OF SEALING - Jay's 6-Part Series