Skip to main content

«  View All Posts

Roof Installation | Asphalt Shingle Roof

Can You Install New Shingles Over an Existing Asphalt Shingle Roof?

December 22nd, 2023 | 6 min. read

Can You Install New Shingles Over an Existing Asphalt Shingle Roof?

Print/Save as PDF

Getting a new roof is a huge project and, more importantly, a costly one. That’s why homeowners on very tight budgets always ask if they can simply install shingles over their existing asphalt shingle roof. 

The answer to this question is actually a simple one. However, there’s much more to learn before deciding if it’s a good idea. 

For over 30 years, the team at Bill Ragan Roofing has helped homeowners find the right roofing solutions for their problems in a way that fits their budget. Now, I’ll do the same for you.

This article covers the following:

  • Can you install new shingles over an old asphalt shingle roof?
  • 6 things to know before installing new shingles over an old asphalt shingle roof

Can you install new shingles over an existing asphalt shingle roof?

Yes, you can install new shingles over an asphalt shingle roof (called a nail-over reroof) under the right circumstances. Your current asphalt shingles need to be near the end of their lifespan and lying down pretty flat (no lifted or cracked shingles, blisters, or bumps) to get a nail-over reroof. 

Your roof can also only have a few penetrations, a small amount of flashing, and no walls that butt up against your shingles. The truth is that most roofs will not be a good candidate for a nail-over reroof.

However, you won’t know until after a roof inspection from a local roofing contractor

6 things to know before installing new shingles over an old asphalt shingle roof

Now, you know that installing new shingles over an existing roof in the right conditions is possible. However, there are some things you need to consider before setting your mind on this type of reroofing. 

Below are the 6 things you need to know before installing new shingles over an old asphalt shingle roof. 

1. It’s cheaper than a full roof replacement

The main reason homeowners consider installing new asphalt shingles over their roof comes down to cost. This is because a nail-over reroof bypasses a lot of the roof replacement process and roofing components. 

It doesn’t require a full tear-off, dump fees, underlayment installation, new flashing, or new decking. This brings the labor and material costs down, which makes it much cheaper than a full roof replacement. 

Look, I understand everyone has a budget, and a full roof replacement is a huge investment. But if a nail-over is your only option, investing in quality is crucial over picking the cheapest price you can find.

2. A roof can only have a certain amount of shingle layers

You already know that your roof must be in the right condition to install new asphalt shingles over an existing roof. However, the condition of your roof means nothing if your roof already has too many layers of shingles. 

In most states, you’re only allowed to have 2 layers of shingles for fire safety reasons. Even with these restrictions, I still see roofs with 3 or 4 layers today.

This is obviously not recommended, and reputable roofing contractors will always recommend a full replacement if you already have 2 or more layers. 

3. You’ll have a lumpy roof if you upgrade your shingles

If you’re trying to install new asphalt shingles over an existing roof, you probably have 3-tab shingles. Well, if you want to upgrade your 3-tab shingle to an architectural shingle, getting a nail-over roof creates an aesthetic issue. 

This is due to 3-tab shingles running on a 5-inch exposure (you see 5 inches of the shingle out of the full 12 inches), while architectural shingles run on a 5 ⅝ inch exposure. The size difference may seem incredibly small, but it creates a hump on your roof every 8 shingles. 

Because of this, I recommend using the same type of shingle when nailing over existing shingles.

4. Your current roof flashing has to be reused

Roof flashing is metal placed anywhere shingles butt up against something, such as a wall, chimney, or in open valleys. It’s one of the most important roofing components to prevent water from getting into your home. 

rusted and damaged roof flashing

When installing new shingles over old asphalt shingles, you have to rely on the past roofing contractor’s flashing job. If the metal’s integrity is compromised or the work was done poorly, do not consider a nail-over reroof. 

Reusing old roof flashing is just asking for leaks, so I always recommend replacing it when getting a new roof. 

5. Future roof leaks are harder to track

It takes skill to find, track, and repair roof leaks under normal circumstances. But installing another layer of shingles over old asphalt shingles makes it even harder. 

If water gets under the new layer of asphalt shingles, it goes down your old, finds the path of least resistance, and leaks inside your home. Well, the problem is that the leak could be coming from two different parts of two different roofs. 

This makes it incredibly hard to find the leak's origin, which makes it harder to repair and ensure the roof leak is taken care of the first time. That’s why it’s best to avoid installing new shingles altogether if your current asphalt shingle roof already has roof leaks.

6. Rotten or compromised decking can’t be replaced

Roof decking is the foundation and framework on which your entire roof is installed. After tearing off your old during a full roof replacement, your roofing contractor has a chance to inspect the decking’s integrity.

roof decking after compromised and rotten wood was replaced

If there’s rotten wood or the integrity is compromised, the decking must be replaced before installation can begin. Well, there’s no opportunity to inspect your decking before installing new shingles over old ones. 

If any wooden boards break during installation, the old shingles must be removed to replace the damaged decking and put back on before installing the new shingles again. 

If a lot must be replaced, it adds to the time it takes to complete the project and can even add to the final cost of the job.

How much does a new asphalt shingle roof cost?

After reading this article, you know you can install new shingles over old ones, the right circumstances to get a nail-over reroof, and 6 things you need to know about a nail-over reroof. Just know that I always recommend tearing off your old roof and getting everything replaced.

I understand wanting to save money, especially considering how expensive a new roof is. But as I said at the beginning, most roofs won’t be a good candidate for a nail-over reroof. 

That’s why you need to know how much an asphalt roof replacement actually costs. This helps you prepare for a budget and know how much you’ll need to finance if you want to go that route. 

Check out How Much an Asphalt Roof Costs to learn the budget you’ll need for a full asphalt roof replacement.

New call-to-action

Table Of Contents