The traditional method of installing manhole covers using a mortar joint directly on the manhole is now outdated. It has been shown that this approach is prone to damage under frequent traffic and heavy loads, often resulting in joint failure, surface cracking, and road subsidence.
Thanks to positive field experience, roll-in manhole covers were officially recognized in 2014 by the Federal Ministry of Transport and Digital Infrastructure. They were included in the Additional Technical Contract Conditions and Guidelines for the Construction of Drainage Facilities in Road Construction (ZTV Ew-StB 14), marking them as the current state of the art.
Excerpt from ZTV Ew-StB 14: "Manhole covers in traffic areas must be level. The tolerance for manhole covers is -5mm between the frame and the adjacent traffic surface. For asphalt surfaces, the installation of roll-in manhole covers is preferable."
Advantage of roll-in installation for manhole covers
Level installation of manhole covers—achieved by rolling them into the asphalt pavement—effectively prevents pothole formation. This method minimizes dynamic loads and noise emissions, while also decoupling the cover from the manhole structure. The elimination of the vulnerable mortar joint significantly reduces the risk of damage, and the manhole itself is relieved of excessive stress. Measurements have shown that less than 25% of traffic loads are transferred to the shaft structure.
To further improve stability, the wall thickness of wastewater manholes was increased from 90 mm to 120 mm in accordance with DIN EN 1917 and DIN 4034-1. This adjustment was made in response to the dramatic rise in traffic loads and is now a fundamental requirement for ensuring operational and traffic safety. Roll-in covers complement this development by further reducing structural stress. Today, the use of roll-in manhole covers is standard practice in both new road construction and rehabilitation projects.
But what about road gullies?
For over half a century, road drainage has relied on conventional paved curb gutters with integrated drainage bodies positioned at the roadside. In this setup, the gully tops transfer traffic loads directly into the drain structure below.
In response to increasing traffic loads, some installations have upgraded from Class C 250 to Class D 400 gully tops. However, this reinforcement only addresses the surface component. The underlying structure, often still built with an unreinforced wall thickness of just 50 mm as specified in DIN 4052, remains vulnerable. Damage to the substructure typically goes unnoticed until visible signs appear—such as subsidence around the drain or broken frames—at which point repairs are complex and costly.
From a critical perspective, the current construction method using paved curb gutters is both labor-intensive and costly. A key weakness lies in the direct load transfer from the gully top into the drain body, which accelerates wear and structural fatigue.
Advantage of roll-in installation for road gully tops
The innovative Multitop System Bituplan tops are seamlessly rolled into the road surface, eliminating the need for traditional, labor-intensive paved gutters. Instead, the asphalt is laid directly up to the kerb, saving significant time, material, and labor during installation.
Thanks to this flush integration into the pavement, the top is decoupled from the drain body, preventing direct load transfer. Traffic loads are distributed into the surrounding road structure, significantly reducing stress on the drain. The mortar joint, a known weak point between the top and the drain body, is completely eliminated—resulting in extended service life and lower maintenance costs.
An additional benefit is the integrated PEWEPREN damping insert, which ensures the top remains rattle-free, minimizing noise emissions. This contributes to a quieter urban environment and helps residents enjoy undisturbed sleep, even in high-traffic areas.
