Upgrading Asbestos Siding: Replace It or Install New Siding Over Top?

If your home has asbestos cement siding, you've probably wondered what your options are when it's time for an exterior upgrade.

New vinyl siding being installed on directly top of existing asbestos siding, using exterior insulation - JP Construction Services

Many homeowners are surprised to learn that replacing asbestos siding is not the only option. In fact, if the existing asbestos siding is in reasonably good condition, installing new siding over top of it is often a practical and cost-effective alternative.

So which approach is right for your home?

Let's look at the options.

Option 1: Remove and Replace the Asbestos Siding

The most complete solution is to remove the asbestos siding entirely and install a new exterior wall system. However, this is usually the most expensive option.

While asbestos siding is generally safe when left undisturbed, cutting, breaking, or creating dust from asbestos-containing materials can release fibers into the air. Because of this, removal requires special handling procedures.

Depending on local regulations and project requirements, removal may involve:

• Protective suits and respirators

• Specialized handling procedures

• Careful packaging of debris

• Approved disposal methods

• Additional labor to minimize dust generation

All of these factors increase the overall cost of the project. The advantage of removal is that the wall sheathing and framing behind the siding become fully accessible for inspection and repair before the new siding is installed.

Option 2: Install New Siding Over the Existing Asbestos

Many homeowners don't realize that asbestos siding does not automatically need to be removed. If the existing siding is stable and not falling apart, installing new siding over top of it is often a perfectly acceptable solution.

Because the asbestos remains undisturbed, this approach avoids much of the expense associated with removal and disposal. There are two common methods for installing new siding over asbestos siding.

Method 1: Furring Strips and Insulation

For thicker asbestos shingles, the preferred approach is often to install vertical 1x3 furring strips over the existing siding. Insulation can then be installed between the furring strips before the new siding is applied.

This method offers several advantages:

• Creates a solid and consistent nailing surface

• Helps level out uneven walls

• Allows for the addition of insulation

• Provides excellent support for the new siding system

Because the siding is attached to the furring strips rather than directly through the asbestos, it is often the best choice when dealing with thicker or less uniform asbestos siding.

Method 2: Install Insulation and Siding Directly Over the Asbestos

For thinner asbestos shingles, it may be possible to install insulation and new siding directly over the existing surface without using wood furring strips. This is typically the least expensive option because it requires fewer materials and less labor.

However, it isn't always possible.

The suitability of this approach depends on:

• The thickness of the asbestos siding

• Its overall condition

• Wall flatness

• The type of new siding being installed

Nearing the finish of installing new vinyl siding over existing asbestos siding - JP Construction Services

An experienced contractor can determine whether direct installation is appropriate for a particular home.

Consider the Effect on Windows and Doors

One important consideration when installing over existing siding is wall thickness.

Every layer added to the exterior pushes the finished siding surface farther away from the house.

This can cause windows and doors to appear recessed once the project is complete.

Some homeowners don't mind this appearance, while others prefer to install wider trim around windows and doors to maintain a more finished look.

Additional trim can help keep these areas flush with—or even slightly proud of—the new siding surface. This is largely a design preference, but it's something worth discussing before work begins.

What About Hidden Problems Behind the Asbestos?

One advantage of full removal is that it allows the wall behind the siding to be inspected. When asbestos siding remains in place, any issues hidden behind it will also remain hidden.

For example:

• Water damage

• Wood rot

• Previous repairs

• Structural issues

Example of water-damaged wood under existing siding. While not super common, without removing the existing siding, you simply cannot know for sure if there is water damage or rotted wood.

That said, homeowners shouldn't lose sleep over this possibility. Serious hidden problems behind asbestos siding are relatively uncommon. Most homes with asbestos siding have performed well for decades.

However, it is important to understand that if an issue exists behind the siding, it may remain undiscovered if the asbestos is left in place. It's not something that should automatically drive your decision, but it is one of the tradeoffs between removal and covering.

Which Option Is Right for Your Home?

There is no single answer for every home. If your asbestos siding is deteriorating, falling apart, or if you want the walls fully exposed for inspection, removal may be the better long-term solution.

If the siding is stable and in good condition, installing new siding over top can often provide an attractive, durable exterior at a significantly lower cost.

The best approach depends on the condition of the existing siding, the type of new siding being installed, your budget, and your goals for the project. A qualified siding contractor can evaluate your home's specific situation and help determine which option makes the most sense.

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