Re-roofing or Layover is a process in which the second set of shingles is layered over an existing set of shingles on a roof without taking off the existing layer of old shingles on a roof. A roof can only have one layover done. Therefore, if your roof already has two layers of shingles (layered separately) you cannot have a layover done on top of it.
Since you do not tear off old roofing shingles, a layover can be done much faster and it is supposed to be a cheaper alternative to complete roof replacement.
Layover may be a good option for those homes whose asphalt shingled roof is old enough to be replaced but the overall structure of the roof is sound. The layover may be a choice if there have been minor leaks, but no significant damage due to leaks and there are no issues with mold, mildew, moss, fungus or other growth. However, it is critical to understand that in order for a layover to work you must be replacing or covering your entire roof and not just doing a layover on parts of your existing roof.
However, layover may not always be your go-to option. Without removing the existing layer of shingles, it is often impossible to tell what you will find lurking under them. How much if any of the felt underlayment is covering the decking and if the decking itself is dry. While it is possible to gauge some of the issues by looking through the attic at the underside of the roofing, it is difficult to diagnose a rot or sagging decking from the underside.
When you add a second layer of shingles upon the first you are not only covering up an existing problem instead of fixing it, you might be making it worse by leaving it untreated.
As mentioned above, a layover is only feasible when done on the entire roof. If you will try to do a layover on a portion of the roof, it can cause some unexpected problems with the overall integrity of your roof. Since the reroofed areas of your roof are now thicker than other areas the reroof areas will not match other areas especially at the ridge cap.
It is often a bad idea to do a layover if you already have two separate layers of shingles on your roof. Although you can do it as a DIY project or even find a jack-of-all-trades roofer do it for you, you may be risking a major waste of money since a third layer of shingles may not be secured properly by nailing them to the decking, which can become undone any time any inclement weather hits your house. This may also mean you are simply covering over some existing issues with your roofing rather than addressing them. At American Construction, we will deal with the problem correctly and treat your roofing project, big or small, like it is our own.
The best thing about a complete roof replacement rather than doing a layover is that it could be done at any time. Total replacement should always be the default option when you have more than one layer of shingles on your home’s roof. It is also highly recommended when you suspect the decking to be the main problem with the roof rather than the shingles. If the shingles on your roof are in a bad shape, the more likely scenario is that the decking underneath it is in poor shape as well and is in dire need of inspection and repair rather than being covered up.
In conclusion, layover might be a good option for a roof that has no major issues with leaks or rotten or soggy decking. However, it is impossible to know this for certain without removing the old shingles and homeowners who choose to do a layover without knowing the problems lurking underneath get a rude awakening when those problems crop up after the layover has been done. Your best option is to tear-off your existing roof and have a new roof put on after a thorough examination and eradication of underlying problems.