Contrary to common beliefs that new can not be made to old, is a complete myth regarding mastic asphalt. This is one material that, with the right preparation and application, can be identified and rectified easily. Impact damage and movement cracks are readily seen in this totally seamless waterproofing.
A hot poultice of mastic asphalt can be applied around the defective area heating the old existing enabling to cut out a patch with a trowel down to roof structure. Equally, this can be achieved with a small hand-held battery grinder.
Either option takes away the health and safety hazard of a gas bottle and torch and hot work permit.
Once patch is removed, a break joint can be cut out using mastic asphalt as to lay 2 coats. Sheathing felt will be cut in to patch as a separating membrane. A first coat will be made good to first break joint, then when cold, top coat will be installed, warming and cleaning the old existing lifting and making good with a sand rubbed finish leaving flat and completely waterproofed.