Abstract: A roofing underlay with a nail-sealable waterproof membrane and method of manufacturing the roofing underlay are described. The roofing underlay includes a main layer formed of a fibrous non-woven material including a plurality of continuous randomly oriented entangled fibers. An anti-slip layer and an anti-skid layer are bonded to the main layer. The main layer is compressed between the anti-slip layer and the anti-skid layer to create a nail-sealable waterproof membrane via capillary action of the continuous randomly oriented entangled fibers of the main layer.