“Why can’t you just put the new shingles over the old ones?"
“Taking off the old roof just costs extra and makes everything take longer!” If you are a homeowner facing the prospect of a new roof, this thought has probably crossed your mind. If it has, chances are, it is for one of two reasons:
- You are hoping to save money by reducing the work and duration of your re-roof.
- You are nervous about hiring a contractor and are afraid you may be going through the same process again – far sooner than you would like (or should be expected).
These are two understandable concerns- particularly since there are differing opinions in the industry about the subject. There are roofing companies that will roof over your existing shingles (note: this conversation doesn’t really apply to tile or metal) in certain situations. However, there are several reasons why it is always better to remove your existing shingles when installing your new system.
Shingles must be laid as flat as possible to be effective.
Typically, if a roof is in need of replacing, the old shingles are lifting, curling, or are even missing in places. This means the new shingles are not going to lay flat enough to create the watertight seal they need in order to do their job and be effective at protecting your home from leaks and other potential problems.
Shingles add weight to your roof.
Did you know that every 100 square feet of quality roofing add 350 to 450 pounds to your roof?! While homes with tile roofs are structurally engineered to support the weight of a heftier roofing system, most shingle roofs are not. Why run the risk of damaging the structural integrity of your rafter system and plywood decking just to save a bit of money in the short term? Removing the old, damaged roof will ensure your roof is bearing the weight it was intended to handle and prevent any “sagging” in your roof’s appearance.
A tear-off will allow the contractor to inspect the decking.
If your home has a leak, the problem may not be effectively addressed by repairing the shingles. If there are additional challenges with the roof, they may return shortly after the initial attempt at repair. Often, the plywood decking on an aged roof needs to be replaced. If your shingle over the current roof, there will not be an opportunity to inspect (address) the decking and make the necessary replacements. The same can also be said for flashings and other critical components of the roof system. To be truly effective, work needs to be carried out on the wooden decking – rather than just piling more shingles on top.
Does your roof meet the most current building codes?
If your home is needing a new roof, chances are, it has a bit of age on it. Building codes change and, if you are planning on selling your home at any time in the future, it will have to meet the most current code requirements. More so, updating the entire structure of the roof- rather than just adding more shingles on top- is the best way to protect your home when facing a severe weather event.
Your roof could keep growing.
Are there dark streaks on your current roof? This is algae growth. When you install new shingles over this growth, you will provide these algae habitats with optimal growing conditions. The more the algae continues to grow, the more they will break down the new shingles from underneath outward.
The new roof may not last as long.
Are you looking at a 30-year shingle for your new roof? Installing it over your old roof may make that irrelevant. If the second layer of shingles is installed over an older, “dried” out layer of shingles, this can cause the new shingles to “dry out” prematurely. This is likely to cause your new roof to break down a lot sooner than it should.
Incorrect reroofing may void warranties…
or create problems at inspection time. Roofing warranties are typically only valid when installed to the manufacturer’s specifications by a licensed contractor. Those specifications often nullify a warranty if they are installed over a failing (old) roofing system. Additionally, if you are looking to sell your home in the short term, trying to cut corners by installing a new roof over the old one, will be discovered at inspection time and reported to any potential buyers. A potential buyer is probably not going to want the cost and hassle associated with removing two sub-standard roofing systems.
Roofing over your existing shingles: consider the consequences!
Getting a new roof is a major construction project that can be expensive and inconvenient. However, while some roofers are willing to just add shingles over your current roof, there are numerous reasons why this can become more costly and problematic for you in the future. It is important to fully weigh the options, and understand the consequences, before moving ahead with roofing over your existing shingles.