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Warm Ballasted System
In a warm ballasted system, the thermal insulation is placed beneath the primary waterproofing membrane.
This type of system has a number of advantages, including reduced insulation thickness and vapour diffusion.
A typical warm ballasted construction will consist of:
- A structural deck
- Vapour control layer
- Thermal insulation
- Sarnafil G410-EL or Sarnafil TG66 membrane
The vapour control layer will generally be a polyethylene-based product (such as Sarnafil EcoVap E or Sarnavap E), with all overlapping joints sealed with Sarnavap tape. If a bituminous vapour control layer is used, it must be fully adhered to the substrate with either Sarnacol 2142s, synthetic cold bitumen or hot bitumen (if insurance permits the use of this method).
Thermal insulation board, meeting the requirements of BS 6229 : 1982 ‘Code of Practice for flat roofs with continuously supported coverings’ (such as SarnaTherm), will be loose laid over the vapour control layer and the membrane loose laid over this, with all joints overlapped by 80mm and hot air welded. At all perimeters and most penetrations, the membrane is mechanically fastened with Sarnabars attached with SBT tubes and suitable fasteners to either the substrate or the abutting upstand.
On top of the finished waterproofing membrane Sarnafil Ltd recommends the use of a protection fleece (such as Sarnafelt Type T), between the membrane and the ballast, to reduce the risk of damage to the waterproofing by any sharp ballast. The finished surface ballast is typically either 18 – 40mm round washed gravel ballast, paving slabs or roof greening such as SarnaVert. Timber decking can also be used on top of the membrane, but an alternative method of attaching the membrane may be required due to the low weight of the timber.
© 2006 Sarnafil Ltd. Legal Disclaimer
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