Breathable Membrane is a triple layer fabric, which ensures full moisture vapour permeability, whilst maintaining the highest levels of water resistance. A high performance breather membrane it is made from high tensile spun bonded polypropylene layers, around a micro-porous poly propylene film. Designed for use in a fully supported or unsupported tiled, slated or metal roof system. KDB Breathable Membrane has a printed grey upper surface and white underface.
The high vapour permeability and waterproof nature of the membrane, combined with excellent tensile/tear strength, make Breathable Membrane an ideal product for use in both warm and cold roof applications. Breathable Membrane is equally suitable whether draped unsupported over rafters or laid directly over insulation. It will allow the escape of water vapour from within the roof structure whilst protecting against wind driven rain, snow and dust, which may penetrate the main roof waterproofing, providing a permanent quality breather underlay, which will last the life of the roof construction.
Cold and warm roof application- Three layer spun-bonded membrane
- Clean and easy to use
- Lightweight and Flexible
- Excellent tensile strength
- UV Stable for up to 4 months
- Grey surface prohibits glare
- Requires no ventilation
| Roll Weight (kg) | 6.2 |
| Weight g/m² | 115 |
| Roll Length (m) | 50 |
| Roll Width (m) | 1 - 1.5 |
| Roll Area m² | 50 - 75 |
| Colour | Grey |
| Tensile Strength MD | 26 0N / 50mm |
| (ISO 9073 - 3:1989) TD | 17 5N / 50mm |
| Elongation MD | <43% |
| (ISO 9073 - 3:1989) TD | <73% 14 0N |
| Nail Tear MD | 14 3N 15% |
| (MO AT 27) | 15 9N 15% |
| Hydro static head (BS EN 20811) | > 15 000 mm |
| Water (Moisture) Vapour Transmition | 1258 g/m² / 24h |
| Fire Rating (BS 3177) | B2 (Pass) |
| UV Resistance | 4 months |
Breathable Membrane must be installed in accordance with the relevant sections of BS 5534: Part 1:1997 and KDB fixing instructions.
Breathable Membrane when installed as a fully supported system, is laid over the support and secured with counter battens, alternatively the membrane can be installed over counter battens and fixed at 200mm centres using corrosion resistant straps or galvanised clout nails. Tiling battens are fixed to the counter battens leaving an airspace between the roof sheet underlay and the tiles for drainage and ventilation.
Abutment flashing should be wedged into a mortar joint 25mm deep and at least 150mm above the level of the slates or tiles.Breathable Membrane underlay should be turned up behind the flashing at least 100mm to prevent rain and snow being blown into the roof-space. Lap joints in the membrane should be generally in accordance with the table set out below. 600mm reinforcing strips should be fixed at hips, ridges and valleys.
Breathable Membrane has UV resistance for up to 4 months. Correctly installed it will provide temporary weather protection, prior to the application of the main roof finish. If Breathable Membrane is to be dressed into a half round external gutter we recommend an eaves protection strip be used.
| Roof Pitch | Min. Horizontal Lap Partially Supported (mm) | Min. Horizontal Lap Fully Supported (mm) | Minimum Horizontal Lap (mm) |
| 12.5° - 14° | 150 | 225 | 100 |
| 15° - 34° | 100 | 150 | 100 |
| 35° + | 75 | 100 | 100 |