At times, a new shingle roof can be laid over an existing one without sacrificing strength, durability or aesthetic appeal. The building must be able to bear the weight of two systems, and the layers down to the sheathing must be in good condition. Since the installation requires no tear off or disposal procedure, the cost of the new roof is very reasonable. Building codes usually let property owners have two layers of asphalt shingles on flat roofs and three when the pitch is higher than 4:12. Most Fort Worth roofing companies are willing to lay shingles over old roof coverings if the circumstances allow it. Whether the units are organic or fiberglass based, technicians can position them by using either the bridging or nesting method.
The bridging process begins at the roof's lower edge and follows a basic pattern according to the manufacturer's exposure recommendations. Metric size shingles are placed on top of standard ones. For the starter strip, the tabs are cut from the shingles so that the installed segments are just under eight inches wide. All the following courses require full width shingles. Since the tops of the new shingles rest on the butts of the older, smaller ones, telegraphing may occur. The unsupported area where the large shingle bridges the bottom of the existing one can be easily damaged by the impact of hail, strong winds and flying debris.
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Nesting helps to prevent the existing shingles from telegraphing through the above units and becoming visible on the roof surface. The tops of the new shingles are fitted along the bottom edge of the above course. The starter strip consists of shingles that are five to six inches wide. For the first course, the roofer should use ten to twelve inch units. From there, full width shingles and increased exposure are appropriate. The system's total shingle exposure, however, is less than that of the bridging method. The nesting approach also requires more materials than the bridging technique and is used when the old and new shingles are the same size.
If the job is done correctly, then the new roof should last a long time. Although multiple shingle layers sometimes increase the amount of heat radiated into the building's interior, they also reduce the likelihood that water will seep into the attic space. The installation of a new roofing system on top of an existing wood surface does not always work well because it can appear to be lumpy. Shingles laid over shingles is normally the best bet for the property owner who wishes to avoid the liability and expense of a complete tear off.