INSTALLATION OF LAYERS OF NON-WALKABLE FLAT ROOF WITH PVC ROOFING MEMBRANE
1. Relevant standards
EN 13984 (2013) Flexible sheets for waterproofing - Plastic and rubber vapour control layers - Definitions and characteristics
EN 13162 (2012) + A1 (2015) Thermal insulation products for buildings - Factory made mineral wool (MW) products - Specification
EN 13956 (2012) Flexible sheets for waterproofing - Plastic and rubber sheets for roof waterproofing - Definitions and characteristics
and other standards mentioned in these standards.
CEN/TS 1187 (2012) Test methods for external fire exposure to roofs
EN 13501-1 (2018) Fire classification of construction products and building elements - Part 1: Classification using data from reaction to fire tests
EN 13501-5 (2016) Fire classification of construction products and building elements - Part 5: Classification using data from external fire exposure to roofs tests
The roof layers should be in accordance with the architectural design and fire protection design. The layers should be compatible with each other.
The vapour barrier should meet the following requirements:
- Water vapour transmission properties, water vapour diffusion equivalent air layer thickness Sd (EN 1931): unless otherwise defined by the execution design, Sd ≥ 200m
- Tensile strength / Elongation: ≥130N/50mm (EN 12311-2)
= Tear resistance: ≥60N (EN 12310-2)
Hard rock wool boards should be non-combustible, class A1 or A2 according to EN 13501-1 (Reaction to Fire Classification). The required thermal conductivity coefficient (λ) and thermal insulation thickness are defined in the architectural design.
Thermo insulation boards should be declared by the manufacturer for flat roofs, which means that the density is 150-185 kg/m3 and compressive strength (EN 826) not less than 50kPa.
If two layers of thermal insulation boards are used, the upper layer with a thickness of 40-50 mm should have a density of 175-205 kg/m3 and compressive strength not less than 70kPa and the lower layer should have a density of 105-135kg/m3 and compressive strength not less than 35kPa.
PVC membrane should meet the following requirements:
- Water tightness: in accordance with EN 1928
- Visible defects: in accordance with EN 1850-2.
- External fire exposure: Broof (T1) (CEN/TS 1187, EN13501-5)
- Joint peel resistance: ≥300N/50mm (EN 12316-2)
- Joint shear resistance: ≥500N/50mm (EN 12317-2)
- Tensile strength / Elongation: ≥1100 N/50mm / ≥10% (EN 12311-2)
- Resistance to impact (Method A and B): ≥600mm (EN 12691)
- Resistance to static load (Method B): ≥20kg (EN 12730)
- UV exposure: in accordance with EN 1297
- Tear resistance: ≥150N (EN 12310-2)
- Dimensional stability: ≤ 1.0% (EN 1107)
- Foldability at low temperature: ≤ -20°C (EN 495-5)
- Hail resistance: ≥25m/s (EN 13583)
The roof areas where people walk to service the equipment on the roof, should be covered with an additional non slip membrane, at least 1m wide, which is also based on PVC (compatible with the basic roof membrane). This additional membrane should have enhanced mechanical characteristics and resistance to weather conditions, it should be welded to the basic roof membrane using hot air welding equipment and protect roof membrane from damage.
Before the start of work, contractor is obliged to submit manufacturer's certificates for all materials to the Supervisor for approval, through the Submittal process.
Contractor is to submit manual for maintenance and cleaning.
Before starting the works, the contractor should check whether all previous works have been completed (installation works, installation of equipment, drains, auxiliary structures, antennas, lighting protection etc.).
The surface where the works are performed should be dry, undamaged, without cracks and cleaned. It should be checked that all unnecessary openings are patched. The edges between the horizontal and vertical surfaces should be prepared for the installation of a vapour barrier or waterproofing membrane (the radius should be in accordance with the requirements of the manufacturer's technical instructions).
Rolls of waterproofing material should be stored in the conditions recommended by the manufacturer. Until installation they should be protected from direct sunlight, rain, snow and mechanical and chemical damage. Thermal insulation boards should be protected from rain before and during the execution of works.
After the slope layer is done, it should be carefully checked whether the falls towards the drains are in accordance with design.
It is forbidden to walk on the materials for insulation works during and after the works, while the materials are still not protected, except for the workers who perform the works.
Vapour barrier is placed on a profiled load-bearing trapezoidal steel sheet or a slop layer made over a reinforced concrete slab. The overlaps of the vapour barrier should be not less than 5 cm and connected with appropriate adhesive tape for connecting the foil.
If the thermal insulation boards are laid in two layers, the boards of the upper layer must be moved by half of the board in relation to the boards of the lower layer, both in length and width, i.e., the joints of the top and bottom layers must not coincide.
If lean concrete slope layer is applied above thermal insulation boards, PE foil with 5 cm overlaps should be placed over the thermal insulation. PE foil joints should be sealed with waterproof tape. Geotextile felt 300gr/m2 should be laid over the slope layer and under the waterproofing membrane.
PVC membrane can be mechanically fixed or not (if a ballast layer, such as gravel, concrete tiles, ceramic tiles on the screed etc, is provided over the waterproofing membrane).
If the PVC membrane is not fixed mechanically and unless otherwise required in the manufacturer's instructions, the overlaps should be 5 cm and welded by hot air welding machine. The homogenous seam should be as strong as the membrane itself.
For hot air welding there is no general limit for working at lower temperatures. It is crucial that the sheet can be rolled out without wrinkles and the temperature difference between the single membrane and the hot air does not become too great (this leads to wrinkles outside the welding zone). If material is stored in a warm location and have temperature of at least +5°C - 15°C, when the waterproofing is installed roll by roll, work can proceed at low temperatures.
If the PVC membrane is mechanically fixed to the supporting trapezoidal sheet or reinforced concrete slab, the overlaps should be at least 10 cm unless otherwise required in the manufacturer's instructions. A combination of a plastic tube and an integral washer in conjunction with the steel fasteners, appropriate for the existing base, should be used for fixing. The edges on which the fixing was performed should be overlapped by the adjacent membrane sheet and weld with a hot air welding machine.
A wind uplift calculation should be carried out to determine the quantity of fasteners required per m2 with regards to corners and perimeters.
Vertical PVC membrane on the roof attic walls is placed over the vapour barrier and thermal insulation boards. The thickness of thermal insulation should be in accordance with the design, the thermal insulation boards should be mechanically fixed. Corner profiles prepared for membrane welding should be placed on the edges between the attic wall and the horizontal surface of the roof.
PVC waterproofing membrane must be separated from all incompatible materials. Joints of PVC waterproofing membrane and EPDM waterproofing tapes from the aluminium-glass facade system, where it is necessary, should be made by welding a tape which is compatible with EPDM, not less than 15 cm wide, for the PVC membrane at the top of the attic wall. EPDM tape from the facade system is then connected to this tape.
If PVC membrane is covered with gravel, PE foil should be placed over the membrane. The thickness of the gravel layer must not be less than 5 cm. Gravel granulation should be 8/16 and 16/32mm.
In order not to damage PVC membrane when cleaning the snow, a layer of snow with a minimum height of 10 cm should be left on the roof.
4. Supervision and measurement of works
All executed works should be regularly checked before they are covered. Control inspections should be performed and the checklists signed by the responsible person previously appointed by the contractor. Supervisor to be notified of each inspection at least one day in advance.
The seams should be checked after the completion of works in a certain zone of the roof. Welded seams must be pre-cooled to ambient temperature. The seams are checked with a seam probe, which should slide continuously along the seam with little pressure. When a deficient weld is detected, it should be immediately visibly marked and repaired as soon as possible.
Works on laying thermal insulation boards and hydro insulation material on flat roofs are calculated per m2 of actually covered area. Laying on vertical surfaces is also calculated per m2 of covered area, noting that waterproofing up to a height of 20 cm is calculated as horizontal waterproofing and the rest (above a height of 20 cm) as vertical waterproofing.
When measuring and calculating the waterproofing material, the openings are not rejected if they are smaller than 3 m2. For openings larger than 3m2, an area over 3m2 is deducted.
Please note that the technical specifications on this web site are templates only, information provided should be carefully checked and aligned with your project needs.
Sd value is simply a measure of how much resistance to moisture diffusion the medium has, when compared to a meter of air. The unit of measurement is meters.
Resistance to roof penetration (for green roofs): in accordance with EN 13948
EN 1847 prescribes methods for testing membranes for certain chemical agents, if there is a need for such tests.
Water vapour resistance factor of a material (µ-value) is a measure of the material’s relative reluctance to let water vapour pass through and is measured in comparison to the properties of air (it has no units).
The warranty period for this type of work should not be less than 10 years. The contractor should be licensed for installation by the material manufacturer.