Fixing a Tile Roof Underlay

Fixing a Tile Roof Underlay

Posted By: Fundi Mfalme Blog on 24th of October 2013

Roofing underlays are used underneath the final tile roof covers. They are fixed before laying roofing tiles or shingles so as to prevent any rain water from passing through to the ceiling as the tiles or shingle roof covers may allow water to seep through when broken.  Roofing underlays can be polythene or bituminous in nature or as it is common nowadays plain metal sheets or corrugated iron sheets. The placing of the felt or underlay should be done by a qualified carpenter and with due diligence as this will help to safeguard the ceiling and entire house from any roof leaks. For the roofing felt to function effectively care must be taken when laying it to ensure that it is free from any punctures as these are likely points that water may pass through to the ceiling of the house. When using polythene, it should be heavy gauge and preferably laid in two sheets. This is because the temperature in the roof space may rise thus leading to damages on the felt. The bituminous felt should preferably be the sand blasted type. This is able to take higher temperatures without breaking within the roof space. The felts should be laid smooth from the ridge to the eaves. This prevent them breaking after they become brittle during the cold season. Metal iron sheet has become the most preferred roof underlay in the recent years as it is more durable and reliable. In comparison to polythene underlays it is less susceptible to damage during installation thus preventing the likelihood of any leakages after installation. It is durable, wind- and fire-resistant and practically maintenance-free, but it must be installed properly by a qualified metal roof carpenter as its installation requires specialized skills. However, the options and installation process for metal underlay are largely the same as shingles or other roofing materials. When laying polythene roofing felt, ensure the surface is horizontal and level. The roof structure is first completed then polythene is laid using plastic straps. The straps are nailed on the purlins in a mesh pattern and they should be tight to prevent sagging under water weight.  After completion the polythene underlay is laid on top then the roof battens are nailed onto the purlins according to the tile specifications.  The laying of tiles is then done after testing for sagging or any leaks within the felt.