The Honest Answer: Sometimes, but Not Automatically

The existing wall must provide—or be properly prepared to provide—a smooth, flat and structurally suitable fastening surface. Deteriorated materials cannot simply be hidden beneath new cladding. Water damage, loose boards, unsuitable fastening conditions and poorly detailed openings must be corrected first.

The final decision must follow Gentek’s current instructions for the selected Fairhaven Sound profile, applicable building codes and a project-specific inspection. General industry guidance should never be used to override the manufacturer’s product requirements.

Why the Existing Surface Matters Aesthetically

Fairhaven Sound shakes and scallops use pronounced shadow lines, cedar-like texture and repeating shapes to create architectural character. Those details look most convincing when the courses sit on a flat, consistently prepared wall.

If the surface behind the panels is uneven, the finished elevation may show waviness, irregular transitions or trim that appears overly deep. These effects can become particularly visible in direct morning or evening sunlight.

Scallops require special visual discipline because their curved lower edges establish a strong repeating pattern. Shake courses are somewhat more irregular by design, but they still depend on level layout and orderly transitions.

What PEPA/VSI Guidance Says About Re-Siding

The Polymeric Exterior Products Association’s installation guidance states that siding should be applied over sheathing or another surface that provides a smooth, flat base. For re-siding projects, its guidance also calls for securing loose existing boards and replacing rotten material rather than installing over deterioration.

PEPA’s manual provides general industry practices, primarily for vinyl siding. Fairhaven Sound is identified by Gentek as polypropylene siding. That distinction matters: PEPA specifically advises installers to follow a manufacturer’s instructions when a specialized product has different or additional requirements.

In practical terms, PEPA/VSI information is a useful quality-control foundation. Gentek’s current instructions remain the controlling product resource.

Conditions That May Support an Overlay Installation

An experienced contractor may consider leaving existing siding in place when all relevant conditions can be verified. Those conditions may include:

• The existing wall is dry, sound and free of rot.
• Loose materials can be securely fastened or properly removed.
• A smooth, flat installation plane can be established.
• The new fasteners can reach an approved structural fastening base.
• Window, door and corner depths can be detailed cleanly.
• Flashing can be correctly integrated with the water-resistive barrier.
• The increased wall thickness will not interfere with rooflines, utilities or accessories.
• Gentek’s instructions and local codes permit the proposed wall assembly.

Meeting one or two of these conditions is not enough. The wall assembly needs to work as a complete system.

When Removing the Existing Siding Is Usually the Better Decision

Removal creates additional labor and disposal costs, but it can expose conditions that should be addressed before a new exterior is installed. Removal deserves serious consideration when:

• The existing siding or underlying wood shows rot, softness or moisture staining.
• The wall is visibly uneven, bowed or heavily patched.
• Several previous siding layers are already present.
• Windows or doors have questionable flashing details.
• The homeowner wants to inspect or upgrade the water-resistive barrier.
• Exterior insulation is being added as part of the project.
• The additional thickness would create awkward trim or accessory projections.
• The contractor cannot confirm an adequate fastening base.

The Fastening Base Cannot Be Assumed

The material visible on the outside of a home does not reveal everything behind it. Existing siding, foam sheathing or another nonstructural layer may not provide the holding power required for the new cladding.

PEPA guidance explains that foam plastic sheathing does not count as a nail-holding material. Where foam is present, fasteners generally must be long enough to pass through it and penetrate an approved structural material as required by the manufacturer and applicable code.

Fastener type, length, spacing and penetration are technical specifications—not reasonable places to improvise. They should be established for the actual wall before installation begins.

Water Management Must Remain Continuous

Siding is not the wall’s only defense against water. PEPA recommends installing polymeric siding over a continuous water-resistive barrier, with code-compliant flashing integrated around windows, doors, corners and roof-to-wall intersections.

An overlay can make these connections more complicated. Existing window flashing may not integrate correctly with a newly added water-resistive barrier. Exterior thickness changes can also affect mounting blocks, light fixtures, vents and utility penetrations.

A proposal that discusses only the visible siding panels is incomplete. The scope should explain how water will be managed behind them.

Pay Special Attention to Windows and Doors

Adding material over an existing exterior moves the finished face of the wall outward. Without thoughtful detailing, windows and doors can begin to look recessed or surrounded by oversized trim.

Before approving an overlay, ask to see how the contractor will handle:

• Window and door head flashing
• Jamb and sill transitions
• J-channel or manufacturer-approved receiving accessories
• Existing decorative trim that will remain
• Mounting blocks for lights, outlets, faucets and vents
• Changes in depth where shakes meet horizontal siding

These are performance details, but they are also design details. Clean openings help a shake or scallop exterior feel intentional rather than layered over an older house.

Overlay Versus Removal: A Practical Comparison

Five Questions to Ask the Contractor

1. What is the condition of the existing siding and the wall behind it? Ask how that condition was evaluated and what remains concealed.
2. What material will receive the fasteners? The answer should identify a suitable fastening base rather than merely naming the old siding.
3. How will you create a flat installation surface? Ask whether damaged areas, projections or uneven courses require removal or correction.
4. How will the water-resistive barrier and flashing be integrated? Pay particular attention to windows, doors, rooflines and penetrations.
5. Can I review a window or transition detail before work begins? A drawing or small mock-up can expose bulky or awkward trim decisions before the entire home is covered.

Does an Overlay Improve Resale Value?

No installation method guarantees a particular resale return. Buyers and inspectors may care about the exterior’s appearance, its documented condition and the quality of the work behind the visible finish.

Keeping photographs of the wall preparation, water-resistive barrier, flashing and fastening details can provide useful maintenance records. Documentation is especially valuable when the original siding remains concealed beneath the new exterior.

A lower initial price is not automatically the better investment. The stronger proposal is the one that explains how the wall will remain flat, dry, securely fastened and visually well-proportioned.