General Ballast Roof

Sika Plan roof waterproofing sheets that are intended for use under ballast have to operate in a completely different environment to those that are exposed. Therefore, a different formulation, Sika Plan Type SGmA, was developed for this purpose. 

Ballast laid at a minimum rate of 80kg/m2 is the minimum satisfactory level to resist wind uplift forces. 

Ballast commonly takes the form of large well rounded gravel or concrete pavers. The potential load of the ballast needs to be taken into account when designing the structural supports for the roof construction. Gravel imposes a dead load of approximately 80kg/m2 and concrete pavers 110-125kg/m2 . 

In the case of green or garden roofs, the growing medium and its associated drainage layers, etc form the ballast, the likely dead load, including retained water, will need to be ascertained specifically for each application. Equally important is the dead load in ‘dry’ conditions and whether it will be enough to restrain the waterproofing membrane against the expected wind uplift forces. 

Timber decking is another form of ballast, which is generally not heavy enough to meet the minimum dead weight requirements, so special measures are necessary during installation, see later in this section.