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Inverted Ballasted System
An
inverted system places the thermal insulation on top of the primary waterproofing.
This
results in the insulation providing a protection layer for the waterproofing. However, this requires
a greater thickness and limits the choice of insulant to Extruded Polysterene (XPS).
A
typical inverted construction beneath the ballast will consist of:
- A structural deck
- Cushion
Layer, if required
- Sarnafil
G476-20 TEX or Sarnafil TG66 membrane
- Thermal insulation
- A
filter layer such as Sarnafelt Type T
No
vapour control layer is installed. Instead, the main roofing membrane provides this function.
The thermal insulation board must meet the requirements of BS 6229 : 1982 ‘Code of Practice for
flat roofs with continuously supported coverings’ and will be loose laid over the membrane.
Ballast
typically consists of either 18 – 40mm round washed gravel ballast or paving slabs. A green roof
can be installed over an inverted roof, but thermal performance of the insulation and vapour drive must
be carefully considered.
© 2006 Sarnafil Ltd. Legal Disclaimer
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