The origin of ventilation errors in sheet metal standing seam roofs

Why is the ridge often insufficiently ventilated?

The origin of ventilation errors in sheet metal standing seam roofs lies with suppliers of the NAILSTRIP system, or the more commonly known designation KLIK. Their system ventilation contains insufficient airflow that does not comply with current regulations according to standard ČSN 73 1901.

A roof with sheet metal covering (tile sheet or standing seam covering) follows this principle:

“The smaller the slope, the larger the ridge ventilation area must be.”

Elements for proper roof ventilation installation

Hip ventilation
Ventilation under the parapet of a mono-pitch roof
Ventilation ridge
Ventilation strips at the eave
Brackets for fixing the ridge batten (30 x 50 mm) at the ridge

According to DIN 4308 Part 3 (German roofing standard), for a roof length of 10 m, ventilation must not be less than 200 cm2/bm. In our conditions, this means that the height of the counter-batten should be at least 6 cm.

Gable roof from 25 to 45 degrees

slope length 6 metres
ventilation gap height at least 40 mm
ventilation outlet through the ventilation ridge 440 cm2/m of roof/ridge

Gable roof with slope up to 22 degrees

slope length 6 metres
ventilation gap height at least 40 mm
ventilation outlet through the ventilation ridge 660 cm2/m of roof/ridge

Mono-pitch roof

slope length 6 metres
ventilation outlet through the ventilation ridge 660 cm2/m of roof/ridge

What options do we have for ridge ventilation?

carpentry preparation by raising the ridge
system sheet metal elements

The advantage of a system ridge element is primarily faster installation and a slimmer construction, which looks better on a roof than a wide ridge formed by boarding. This system element is made from a single piece and is anchored with screws or rivets.

Manufactured from aluminium material with a thickness of 1 mm and available in all colour finishes to perfectly match the roof covering. Thanks to the grooves, ridge tiles can be quickly and precisely joined without the need for further adjustments. Front ridge end caps and ridge splitter sets are available as optional accessories. A perfect, universal alternative ridge tile that meets all roof ventilation criteria. The UNI ventilation ridge tile is designed to allow efficient air circulation under the roof covering. This extends the lifespan of the entire roof and ensures optimal conditions for the roof structure and thermal insulation. A special feature is the self-supporting labyrinth ventilation opening with a removable cover and a ventilation cross-section of 300 cm²/m. The ridge covering length is 1,220 mm.

Source: Rheinzink, Yuri Nushtaiev

Eave ventilation

Ventilation grille

It is natural that everyone wants to save money when building or renovating a roof. In such cases, the selection of ventilation grilles also comes into play. Many roofers have experience with rodents damaging ventilation grilles and gaining access to the roof space. This is the main argument for using aluminium ventilation grilles on a roof. These are manufactured in natural aluminium, but also in a double-sided colour finish in red-black and brown-white combinations. The advantage is the square perforation, which ensures adequate roof ventilation, and thanks to the narrow openings, the entry of pests and insects into the roof space is prevented.

Technical parameters

According to DIN 4308 Part 3 (German roofing standard), for a roof length of 10 m, ventilation must not be less than 200 cm2/bm.

Ventilation grille 50 mm has a ventilation area of 185 cm²/m
Ventilation grille 80 mm has a ventilation area of 300 cm²/m
Ventilation grille 100 mm has a ventilation area of 393 cm²/lfm

An L-PROFILE can also be made from aluminium grilles. This ensures that the grille is stable along its entire length and will not warp. This has primarily an aesthetic advantage. However, if you install it in the roof as shown in the image below, you will enlarge the ventilation opening and gain a larger ventilation area for the ventilated space. You will appreciate this especially in summer, when the roof needs even more ventilation.