How to Install Flashing Under Siding Like a Pro: Expert Tips and Step-by-Step Guide

ByGeorge Orwell Updated

How to Install Flashing Under Siding?

To install flashing under siding, you will need metal flashing pieces or coil stock, flashing tape, shears, and a hand seamer (a siding brake is optional).

First, cut a piece of flashing to the desired length.

Install the siding over the flashing, making sure to leave a small gap at the bottom for water drainage.

Slide the pan flashing under the end of the siding, with the upper leg extending at least 4 inches.

Secure the flashing and siding to the structure using nails or screws.

It is important to use metal flashing behind butt joints to protect against water intrusion and UV degradation of housewrap.

Additionally, Z-flashing should be used over horizontal wood trim and decorative trim bands, while step flashing is needed at roof and wall intersections and should be installed behind the siding.

Key Points:

  • Prepare the necessary materials:
  • metal flashing
  • flashing tape
  • shears

  • hand seamer

  • Cut a piece of flashing to the desired length.

  • Install siding over the flashing, leaving a small gap at the bottom for water drainage.

  • Slide the pan flashing under the end of the siding, with the upper leg extending at least 4 inches.

  • Secure the flashing and siding to the structure using nails or screws.

  • Use metal flashing behind butt joints, use Z-flashing over horizontal wood trim, and use step flashing at roof and wall intersections.

Did You Know?

1. The first known use of flashing in construction dates back to ancient Egypt, where they used a combination of bitumen and reeds called “pupo’adu” to waterproof their buildings.
2. While most flashings are made of metal, such as aluminum or copper, some modern alternatives use synthetic materials like PVC or rubber. These materials offer improved flexibility and durability in extreme weather conditions.
3. The term “flashing” originates from the Old English word “flesc,” meaning “flutter,” which refers to the action of diverting water away from a structure through the use of a thin, flexible material.
4. Flashing serves various purposes beyond water diversion, such as preventing the infiltration of pests, improving insulation, and reducing energy loss by sealing gaps between the siding and the structure.
5. Proper installation of flashing requires a technique called “kickout flashing,” which redirects water away from the intersection between the roof and the siding, preventing potential water damage and maintaining the integrity of the building envelope.

Tools For Installing Flashing Under Siding

Flashing is a crucial component for protecting homes from moisture intrusion during siding installation. To ensure a successful installation, it’s important to have the right tools on hand. Here are the essential tools you will need:

  • Metal Flashing Pieces or Coil Stock: Metal flashing is typically made of aluminum or galvanized steel and comes in various sizes. It is used to create a waterproof barrier between the siding and the underlying structure.

  • Flashing Tape: Flashing tape is a self-adhesive waterproofing material that can be applied to supplement stock flashing. It is especially useful when the stock flashing does not meet the necessary length requirements.

  • Shears: Shears are essential for cutting the metal flashing to the required lengths. Make sure to use quality shears that can handle the thickness of the flashing material.

  • Hand Seamer: A hand seamer is a tool used to bend metal, ensuring a tight fit and secure seal between the flashing and the siding. While a hand seamer is ideal, a siding brake can also be used as an alternative.

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Using Flashing Tape To Supplement Stock Flashing

To address the issue of stock flashing not meeting the 4-inch upper leg requirement for adequate protection, flashing tape can be used as a supplement. Here are the steps to effectively use flashing tape:

  • Cut a piece of flashing tape: Measure the required length to extend the stock flashing, and cut the tape using shears or a utility knife.

  • Prepare the surface: Clean the surface thoroughly to eliminate any dirt or debris. Use a cloth or brush to ensure a proper bond.

  • Apply the flashing tape: Remove the backing from the flashing tape and carefully attach it to the stock flashing, extending it to the necessary length. Press firmly to ensure strong adhesion.

  • Secure the tape: For a secure seal, utilize a hand seamer or siding brake to press down on the flashing tape, creating a tight bond between the tape and the underlying structure.

Steps For Installing Flashing Under Siding

Proper installation of flashing beneath the siding is essential for maintaining the integrity of your home. Follow these steps for a successful installation:

  1. Cut a piece of flashing: Measure the length needed for the flashing and use shears to cut the metal flashing to the appropriate size.

  2. Install the siding: Begin by installing the siding, ensuring it is properly aligned and secured to the structure. Leave a small gap between the bottom edge of the siding and the flashing, allowing for proper drainage.

  3. Slide the pan flashing: Slide the pan flashing under the end of the siding, ensuring it extends beyond the edge by at least 4 inches. This will create a proper overlap and prevent moisture from infiltrating.

  4. Secure flashing and siding: Secure the flashing and siding to the structure using nails or screws. Make sure the fasteners penetrate both the flashing and the siding, creating a secure attachment.

  5. Remember to measure and cut the flashing accurately.

  6. Ensure proper alignment and secure attachment of the siding.
  7. Leave a small gap between siding and flashing for drainage.
  8. Slide the pan flashing under the end of the siding with a 4-inch overlap to prevent moisture infiltration.

“Proper installation of flashing beneath the siding is essential for maintaining the integrity of your home.”

Metal Flashing For Butt Joints

Butt joints are vulnerable areas where two siding panels meet. To protect against water intrusion and UV degradation of housewrap, it is crucial to install metal flashing behind these joints. Here’s how to do it:

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1. Cut a piece of metal flashing: Measure the length needed to cover the butt joint and use shears to cut the flashing accordingly.

2. Install the siding panels: Begin by installing the first siding panel, making sure it is properly aligned. Apply adhesive caulk to the overlapping edge of the second panel that will butt against the first.

3. Slide the metal flashing: Slide the metal flashing behind the butt joint, ensuring it extends beyond the joint at least 2 inches on either side. This will create a protective barrier against moisture.

4. Secure the siding panels: Secure the siding panels using nails or screws, making sure the fasteners penetrate both the siding and the metal flashing. This will provide a firm and lasting attachment.

– Cut a piece of metal flashing
– Install the siding panels
– Slide the metal flashing
– Secure the siding panels

Z-Flashing For Horizontal Wood Trim

Installing Z-Flashing for Horizontal Wood Trim

Step 1: Measure the Length: Begin by measuring the length of the horizontal wood trim that requires protection. Use shears to cut a piece of Z-flashing to the appropriate size.

Step 2: Position and Align: Place the Z-flashing over the horizontal wood trim, ensuring that it extends at least 2 inches beyond the edge. Make sure the upper leg of the Z-flashing slides behind the siding to create a seal that will prevent water intrusion.

Step 3: Securely Nail: Use nails to securely attach the Z-flashing to the underlying structure. Ensure that the fasteners are tightly fastened to provide effective protection against moisture intrusion.

Step Flashing At Roof And Wall Intersections

At roof and wall intersections, step flashing is essential for preventing water penetration. Follow these steps to correctly install step flashing:

  • Install the first row of siding: Begin by installing the first row of siding, making sure it is properly aligned and attached to the structure.

  • Slide in the step flashing: Slide the step flashing behind the siding, ensuring that each piece overlaps the previous one by at least 3 inches. This will create a stepped effect that diverts water away from the joint.

  • Continue installing siding: Continue installing the remaining rows of siding, making sure to insert step flashing as required at each roof and wall intersection.

  • Secure the step flashing: Secure the step flashing to the structure by nailing it in place, ensuring a tight connection. This will provide a durable and watertight seal.

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Installing flashing under siding is a crucial step in protecting homes from moisture intrusion. By following the expert tips and step-by-step guide provided, you can ensure a professional and effective installation, safeguarding your home from potential water damage.

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Frequently Asked Questions

Do I need flashing at the bottom of my siding?

Yes, it is essential to have flashing at the bottom of your siding. Properly integrating flashing with other wall water management details helps to direct water down and out of the wall, preventing moisture damage. By installing flashing under the bottom edge of the weather-resistant barrier, you can ensure that water is effectively directed out of the wall, enhancing the durability and longevity of your siding.

What is the gap between flashing and siding?

In order to prevent moisture intrusion behind the siding material, it is crucial to maintain a gap between flashing and siding. This gap acts as a protective barrier, typically with a minimum width of 1 inch, ensuring that water does not penetrate the walls. By creating this separation, potential damage caused by moisture can be minimized, prolonging the lifespan of the siding and preserving the integrity of the building structure.

Where is flashing necessary?

Flashing is crucial in areas where roof features, such as vents, chimneys, and skylights, are present. It is necessary to prevent water from infiltrating the roof deck by directing it to the shingles instead. By effectively surrounding these roof features, flashing ensures that water flows down the sides and away from the vulnerable areas, safeguarding the integrity of the roof and preventing potential damage.

What are the essential steps to properly install flashing under siding to prevent water damage?

The essential steps to properly install flashing under siding to prevent water damage involve thorough preparation and precise execution. Firstly, it is crucial to ensure that all siding is properly removed and the area is clean and dry. Next, a waterproof barrier, such as a self-adhesive membrane, should be applied directly under the siding to create an additional layer of protection against water intrusion. Finally, the flashing should be carefully installed, making sure it is secure and properly sealed around all openings, corners, and joints. This will effectively redirect any water that may penetrate the siding, preventing it from seeping into the walls and causing potential water damage.

In conclusion, the key steps in installing flashing under siding to prevent water damage include thorough preparation, such as removing existing siding and ensuring a clean surface, applying a waterproof barrier, and securely and correctly installing the flashing to effectively redirect water away from the building’s structure. Adhering to these essential steps will help safeguard against potential water damage and maintain the integrity of the building.

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