Ballast or protected flat impassable roofs are mainly designed for smaller roofs, in buildings with RC construction.
Characteristic cross-section of this type of roof, from bottom to up would be:
- RC structures in decline or later poured cement screed on the decline
- vapor barrier
- thermal insulation (extruded polystyrene - XPS or polyurethane foam)
- polypropylene geotextile as a separation layer except for TPO and FPO membranes
- PVC, TPO or FPO ballast roofing membrane
- drainage protective layer
- natural gravel (pebble).
Importantly, the roof falls in ballast type roof should be more pronounced, and the recommendation that it has to be minimum 1.5% to the basin level or ideally 2% decline. If RC structures does not have falls, should be approached subsequent preparation of cement screed on the decline.
Thermal insulation in this case ballast roofs recommend closed thermal structure - water-non absorbent structure - extruded polystyrene XPS or sprayed polyurethane foam.
PVC, TPO or FPO ballast roof membranes should be of premium quality, extremely resistant to chemical elements, aggressive compounds in the air, resistant to bacteria and algae. Ballast roofing membranes should be the thickness of 1.5 mm to 2.0 mm and have a distinct ability for each welding..
Protection and drainage layer is a "honeycomb" structure PVC thickness of approximately 1 cm, wrapped in PP filter layer and a protective layer. It serves as a remarkable mechanical protection waterproofing membranes and a fast drainage and storm water runoff.
Roof gravel should be rounded edges (pebble), granulation 16 - 32 mm, washed with water and without air content. The recommended thickness of the fill gravel roof is 6 cm.
In the past, ballast roofs had an advantage over the rooftops with exposed waterproofing membrane, mainly because of technological inability to produce a roofing membrane, which would be a long-term UV-resistant and strong blows. Today this is no longer the case and ballast roofs designed and performed on individual objects for aesthetic reasons, because of the extremely strong winds, higher mechanical protection waterproof cover from falling objects, easier and faster installation of waterproofing membrane without the need for fixing the substrate and the like.
Finally it should be noted that both of these prominent roof system extremely technically justified, long-term and economically advantageous as they rightly more suitable and better solution than any other comparative roof system. The ability to view the roof and relatively easy and inexpensive to repair any inconsistencies, makes these roof systems particularly reliable and long-term.
The exception - except PVC, TPO or FPO ballast roof membrane impassable ballasted roofs like waterproofing covering prefer the quality bitumen membranes ballast in two layers:
- bituminous primer to fully saturate the substrate
- full surface welded SBS bitumen x 2 times.