When contemplating a new roof, many people hope to simply do a shingle over and avoid the extra cost and mess of tearing off the existing roof and starting from scratch. Although that sounds like a good idea, I can assure you that the cons heavily outweigh the pros. In fact, the ONLY pro to a shingle over is the fact that it’s cheaper and cleaner. The problem is, what if there is an unknown leak or bad roof flashing? Will that be fixed? Will the damaged wood be replaced during a shingle over? Unfortunately, the answer is no.
Just the other week, we came across a leak around a dormer that the homeowner never knew about (pic below). Obviously, during the tear off, we spotted the leak and were able to change out the rotted wood and re-flash that area. In a shingle over, if some of the roof decking has buckled and warped over the years, it likely isn’t going to be noticed and fixed. This can lead to increased rot, mold, and decrease the structural integrity of your home.
Long-Term Effects of Shingling Over Shingles
Apart from the problems that can go unnoticed during the actual shingle over, there are long term effects to consider as well. For instance, instead of just one roof on your home, you now basically have two. That’s a lot of weight, putting added stress on the roof decking. Also, two layers of shingles are going to attract a lot more heat than just one layer, which can lead to the shingles prematurely deteriorating. Also, what about all that dark algae growth and bacteria on the original layer of shingles? Now all of that is trapped under a 2nd layer of shingles, again having the potential to shorten the lifespan of the top layer of shingles.
Roofing Over Your Existing Roof Is Not Worth It
If you haven’t noticed yet, we are not fans of shingle overs – not at all. We don’t recommend them and do we do them. Over the years, we’ve seen the problems that can be caused by shingle overs. Does it cost more to tear off? Yes. However, by spending a little more now, you can save yourself thousands in the long run.