Geotec lead underlay is an essential part of your roof structure. Needle punched and non-woven, geotextile polyester materials do not rot or cause adhesion.
First and foremost, its main use is to isolate the lead from the substrate layer, ensuring that the roof structure benefits from the best conditions, providing you with many years of problem-free service.
By creating a gap between the substrate layer and the lead, Geotec lead underlay ensures that there is an adequate amount of airflow between the roof elements. With the airflow ventilating the layers in the roof, any moisture that may have formed is dried effectively, preventing the detrimental effects of damp.
Underlay reduces the drag caused by thermal movement between the substrate layer and the lead sheet. It also allows the lead sheet to expand and contract as temperatures rise and fall, which means the roof structure can move freely without damaging.
Another benefit for lead underlay is it protects against the corrosiveness of the moisture that may leach from concrete/stone and some timbers. If this damages the lead, it may weaken the structure and compromise your roof.
Finally, the lead underlay protects against imperfections in the timber substrates, such as nail heads or knots, ensuring that the structural integrity of the roof and the lead is not compromised.
It also adds a further layer of protection against rain and other forms of precipitation. However, if the roof has been laid properly, it should not be required for this function.
With a roll width of 1 metre and roll length of 25 meters, you have all the information you require to work out how much material you will need for your roof. The constitution of the non-woven polyester felt underlay is 220g per metre squared, making it much lighter in weight than bitumen felts. Even though it is lighter in nature, it does not compromise on water resistance.