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What Happens to Wood Siding Under Vinyl?

October 3, 2023

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wood siding under vinyl

When it comes time to re-side your home, you may be wondering - what happens to the existing wood siding if I install new vinyl siding right over it? Does the old siding need to be torn off first, or can vinyl simply be installed over the original wood? Many homeowners choose to install vinyl siding over existing wood for cost and convenience reasons. 

So, what exactly happens wood siding under vinyl? When vinyl siding is installed over wood siding, the original wood siding generally remains in place underneath the new exterior vinyl shell, provided the wood is properly prepared, and the vinyl is installed correctly to prevent moisture damage.

Understanding what happens to your wood siding when covered with vinyl can help inform your siding installation decisions and prevent headaches down the road.

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Reasons for Re-siding a Home

There are several reasons why homeowners choose to re-side their homes with vinyl siding over existing wood siding:

  • Wood siding can warp, crack, and rot over time, requiring costly repairs and repainting. Vinyl is more durable and requires less maintenance.
  • Older wood sidings like cedar shakes and clapboards allow air infiltration and are less energy efficient. Vinyl siding improves insulation.
  • Vinyl siding comes in a variety of styles and colors, allowing homeowners to update the look of their homes.
  • Vinyl is cheaper than replacing damaged wood siding with new wood siding.

wood siding under vinyl

Preparing Wood Siding for Vinyl Installation

Before installing vinyl siding over existing wood, the wood siding should be properly prepared:

  • Inspect the wood siding and make any necessary repairs to fix rotted or warped boards, cracks, and gaps. This helps create an even surface for the vinyl.
  • Replace any missing or severely damaged boards. Vinyl siding needs a smooth facade to adhere properly.
  • Scrape off peeling paint and re-paint the wood siding if needed. This protects the wood from moisture damage.
  • Install house wrap over the wood siding. This creates a weatherproof barrier between the old and new siding.
  • Install furring strips vertically over the house wrap if needed to create an even surface.
  • Caulk around windows, doors, and other openings to seal air gaps.

Does the Original Siding Stay Underneath?

In most cases, the existing wood siding remains underneath the new vinyl siding. The vinyl is installed over top, essentially creating a protective shell over the wood. This saves time and money compared to completely removing and disposing of the old siding first.

There are a few exceptions where existing siding should be removed:

  • If the wood is extremely warped, buckled, or rotted beyond repair
  • If the old siding is uneven or lacks structural integrity
  • If hazardous materials like asbestos siding are present

Usually, though, vinyl installers prefer leaving the intact wood intact rather than tearing it off. The existing siding provides extra structure and insulation when covered properly.

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What Happens to Wood Siding Under Vinyl? Potential Moisture Risks and Mold are Concerns

Some homeowners worry that trapping wood siding underneath vinyl may cause moisture issues or mold growth. This is a valid concern, as moisture trapped behind the vinyl could cause rot or decay in the wood.

Installing vinyl siding incorrectly can definitely lead to problems:

  • Failing to properly repair or replace damaged boards
  • Not using house wrap or furring strips to create a gap for ventilation
  • Poor caulking around penetrations in the siding

However, when vinyl siding is installed properly over intact wood siding, the risks of moisture issues are low. Here's why:

  • The vinyl siding forms an airtight barrier, keeping outdoor water from reaching the wood.
  • Vinyl siding "breathes" enough to allow small amounts of moisture vapor to escape.
  • House wraps provide adequate ventilation between the vinyl and wood.
  • The intact wood siding has likely seasoned and dried over time already.

With proper preparation and installation, trapping wood under vinyl poses minimal moisture risks. No more than leaving wood siding exposed to the elements. Periodic inspections are recommended, though.

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Signs of Potential Moisture Damage

If moisture issues do arise down the road, there are signs to watch out for:

  • Bubbling or buckling of the vinyl siding
  • Discoloration or staining on the vinyl siding
  • Mold or mildew visible underneath window edges or siding joints
  • Soft spongy spots when pressing on the vinyl siding

Catching moisture problems early is key to preventing extensive water damage. Some repair options include:

  • Adjusting landscaping and drainage to direct water away from the siding
  • Re-caulking around windows, doors, and penetrations
  • Drilling small drainage holes at the bottom of problem areas
  • Cutting ventilation slots in problem areas and refastening the siding

If moisture damage is extensive, siding removal may be needed for repairs. Catching issues quickly improves chances of saving the wood facade underneath.

wood siding under vinyl

Weighing the Pros and Cons of Installing Vinyl Over Wood

Vinyl siding over wood comes with tradeoffs to weigh:


  • Less expensive than full wood replacement
  • Preserves some of the structure of existing wood siding
  • Provides updated exterior with less maintenance
  • Improves weatherproofing and insulation when installed properly


  • Existing moisture damage or rot could go undetected
  • Ongoing moisture risks if vinyl installed incorrectly
  • Loss of original wood siding aesthetic
  • Full siding replacement difficult if problems arise

In summary, installing vinyl over intact, well-prepped wood can offer cost and aesthetic benefits. It is less risky than trapping damaged or rotting wood underneath. Proper installation and ongoing maintenance help minimize potential moisture issues. Weigh the pros and cons carefully for your specific home.

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About United Better Homes

For over 30 years, United Better Homes has been providing quality vinyl siding installation and home improvement services in the local area. Their experienced team handles vinyl siding projects of all sizes, from small garage remodeling to full home re-siding. To request a free estimate for your vinyl siding project, call United Better Homes today at 401-274-0111.


What goes under vinyl siding on a house?

Typically, the existing wood, aluminum, or other original siding on the house remains in place when new vinyl siding is installed over top. To prepare for vinyl siding, the original siding should be repaired, prepped with primer/paint, and covered with house wrap to create a smooth, waterproof surface for the new vinyl to adhere to.

What is the wood under your siding called?

The wood boards used for the original siding on a house are typically referred to as clapboards or weatherboards. These wooden boards that form the exterior facade underneath new vinyl siding are the original sheathing of the home.

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