Roofing Over an Existing Roof: What You Need to Know

When you start noticing issues with your roof, or when it is nearing the end of its lifespan, it is probably time for some big decisions. You may wonder about the roofing options you have, and which one will be the best solution for you. The best thing to do then is to call in a professional roofer and discuss it with them, as they have both the needed expertise and experience to steer you in the right direction.

If the condition of your roof is such that a few repairs will not suffice to get it back into shape, but it is still functional enough that it doesn’t need to be completely torn off and replaced, then you should think about reroofing, i.e. installing a new roof over your existing one. Reroofing is not the same as roof replacement and there are certain conditions that your roof needs to satisfy in order to be a viable candidate for reroofing.

Keep reading to find out all you need to know about reroofing, including how it differs from a roof replacement and what its main advantages are.

Difference Between Reroofing and Roof Replacement

Roofing over an existing roof is also called reroofing or an overlay. It is the process where roofers install a new roof over your existing one, i.e. add a new layer of shingles, which means that there is no tearing off of the old roof. It is important to know that this process can only be done once because you can only have two layers of shingles on your roof.

Roof replacement is the process of installing a completely new roof that includes tear off of the old one. Roofers will tear everything off, down to the deck of the roof, and basically start from scratch with the new roof, from putting felt paper to installing shingles. Since roof replacement includes tearing everything off, it can be done on every roof, no matter the number of shingle layers – they are all going to be removed in any case.

Roof replacement involves much more time and labor, and is, therefore, more expensive than reroofing. When a roof has no underlying problems, when it is old, and is simply losing its function, reroofing might be a better solution as it involves much less work on your home, as well as less money.

When and Why to Put a New Roof over an Existing Roof?

When your roof starts to fail, but it is in an overall good condition, a reroofing might be the best choice for you. What does it mean to have a roof that is failing but is still in a relatively good state? It means that your roof may be at the end of its life, but its underlying structures and sheathing are in a generally good condition. Your shingles may be losing granules and are worn out due to age or weather, but they are not causing leaks, they are not curling or missing. These are all good predispositions for installing a new layer of shingles over the existing one.

By adding another quality layer of shingles on your roof, you are actually adding one more protective layer to your roof. This will, along with the underlayment, roof deck, and the original layer of shingles, function as combined protection from damages and will stop any leaks from coming into your home. We see this layer as an upgrade, or even a rejuvenation of your roof that boosts your leak protection. It will further help to direct the water from your roof and into your gutters and downspouts, preventing the problem of pooling.

Reroofing can also be done when you simply want or need a change on your roof – you may want a different design or color, or you may be completely renovating your home so you want the roof to match your new style. But even if your main goal isn’t redesigning your roof, it will nonetheless gain a new aesthetic appeal. Installing a new shingle layer will give your roof depth and even a three-dimensional appearance, as it is slightly raised due to the existing layer of shingles beneath it.

When it comes to the financial aspect of reroofing, it is undoubtedly less expensive than a complete roof replacement. The main reason for that is that there is no need for a tear off of the old roof – of the existing shingles and the underlying structures. This means that there is significantly less labor needed, as well as time spent on the project, and therefore the costs are lower. Your roofer can immediately start with the installation of the new roof, without spending time on shingle removal and disposal.

When is Reroofing not a Good Idea?

A professional and honest roofing contractor will and should always warn you if your roof is not a good candidate for an overlay or reroofing. That is what a roofing inspection is for and should always be done before any action is taken on the roof.

After a thorough inspection, a roofer will come to you with his report or a recommendation, explaining why your roof is or isn’t up for reroofing. You can ask for a few roof estimates from different contractors just to be sure that you are doing the right thing, so that you can choose the best roofer for yourself.

One of the main and most straightforward reasons when an overlay is not possible is when you don’t have asphalt shingles. Installing a new roof over an existing one can only be done if you have shingles because you can only put shingles over shingles. It is not possible to mix materials, nor to install a new layer over slate or wood tiles.

Another reason is curling shingles, as you can only install a new layer if the first one is completely flat and level. Shingles can curl over time due to different reasons, so if you still want to go with the option of reroofing, you should first get to the bottom of this problem with your roofer and replace the curling shingles.

Furthermore, if you already have two layers of shingles because you have already reroofed once, another layer is not an option, as the roof can get too heavy. And lastly, if there is extensive and visible damage to your roof, you shouldn’t add another layer to cover it, but tear everything completely off and resolve the source of the problem. 


Reroofing is a great option for those who don’t need a complete roof replacement, who have a generally good roof that is at the end of its life cycle or a roof that is slowly losing its function. As opposed to a roof replacement, it does not involve tear off, which means that it reduces both time and cost for the project.

It is always a good idea to consult with a roofer you trust, who can do an inspection, give you an accurate estimate, and advise you on what the best option is for you.

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