Walk-on and trafficable liquid plastic coating systems on wood

The goal of the project is to develop a polyurea-based liquid plastic system that could be applied as durable surface protection for road and walkway surfaces made of wood-based materials, such as bridges.



In the ongoing search for resource-saving construction methods, wood is assuming an increasingly important role as a building material. For the sustainable use of wood in construction to be assured in the long term, there is a need for planning, construction and maintenance specific to this material. In the case of wood, this primarily means long-lasting moisture, weather and fire protection. The project is concerned with the development of a liquid plastic (LP) coating system for roadway slabs made of wood-based materials for use in pedestrian and cycle-path bridges, parking decks or terraces. In the past, LP systems have only ever been used on concrete or steel. They have the advantage that they are significantly lighter than traditional asphalt variants and can also be processed more quickly. This approach to surface protection for roadway or footpath surfaces can be applied to both new constructions and rehabilitation projects. Another advantage is the low processing temperature of approx. 60–70°C compared to asphalt (200–220°C). This prevents the formation of bubbles under the coating, which ensures good adhesion of the coating in the long term. The use of liquid plastic systems provides an eco-friendly alternative to conventional systems and also offers great commercial potential thanks to the wide range of potential applications.

Course of action

The LP system is based on polyurea and is applied to the roadway slabs in a multi-stage process. This creates a 3–4mm coating of plastic that protects the entire slab from the weather and guarantees a high level of durability. After the pull-off adhesion tests of various primers showed very satisfactory results, four coating systems were selected for further testing on this basis. Numerous tests have been performed to date to determine the mechanical and physical properties of various substrate and product combinations, and further tests are ongoing. At least two real-world projects (one bridge and one multi-storey car park made of timber) are currently collecting and evaluating insights on the long-term behaviour of the roadway slab and the coating.


All four systems have demonstrated good applicability on different wood-based materials. The individual values in pull-off adhesion tests to SIA 281/3:2002 were more than adequate for the chosen substrate-system combinations, clearly achieving the target values according to SIA 273:2008, with very good penetration into the substrates. The peel adhesion tests to SIA 281/2:2011 clearly achieve the values prescribed by the SIA 273:2008 standard. Pull-off tests were performed on unweathered test specimens to EN ISO 527-1:2019 and EN ISO 527-2:2012, and on weathered test specimens as specified by the EN 927-6:2006 standard. In addition, the quality of the seal was examined. The tests that have been carried out to date to determine the vapour diffusion resistance according to EN ISO 12572:2016, and to ascertain the thermal conductivity in line with EN 12667:2001, serve the purpose of a building physics simulation to determine the long-term behaviour under various installation conditions and after any damage. Detailed trial results are available from the business partner.

Looking ahead

A directly trafficable test stand will remain installed on the grounds of BFH-AHB on Solothurnstrasse in Biel, for approximately 18 months.