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How to Install Undersill Trim with CertainTeed Vinyl Siding: Video Tutorial

Published on: September 21, 2021

Vinyl siding undersill trim helps secure siding securely to your home. It goes around windows, doors and eaves. You must use these trim pieces on every window that sits above the ground line. 

These trim pieces hide the top edge of your vinyl siding. You’ll get a clean and finished look from your siding project when using undersill trim. But you’ll also get strength and durability to protect your home’s structural integrity. 

Video Tutorial Showing How to Install Vinyl Siding Undersill Trim

Installing undersill trim is fairly simple. The most important element is ensuring that your nail slots align to provide a good seal between your windows and trim.

  1. Start by adding the trim pieces around your window or door. 
  2. Nail the trim in place.
  3. Slide the siding up under the window.
  4. Nail the siding piece into place.
Watch the YouTube video: Installing Undersill Trim with CertainTeed Vinyl Siding for a step-by-step demonstration. 

Tips for a Successful Siding Installation Job

Installing vinyl siding requires precision and planning. Take some time to learn more about the process and what to expect before beginning the project. Here’s a look at a few key success factors to ensure a good installation job.

  1. Start with quality underlayment: underlayment is not just some paper that preps for your siding project. It’s an essential element of protecting your home. Don’t skimp when selecting your underlayment. At 2FL, we use quality materials to protect your home long-term so that your siding project lasts for decades. It’s one area that sets us apart from our competitors and allows us to provide you the best quality siding installation.
  2. Leave room for expansion and contraction: siding is your first line of defense against the elements. As such, it sits in the outside temperatures as they fluctuate. The materials will expand and contract as they heat up and cool down. Avoid cracking, buckling and sagging by allowing for some change to your siding. When attaching the siding, center the nails in the slots so that the siding can freely move side to side. Allow a bit of room between the nail head and the hem but be sure that the nail is driven in perfectly straight.
  3. Install each siding piece straight and level: make sure each panel aligns horizontally. Start with leveling the first piece of siding and then every few rows, check how level your siding is remaining. Be especially mindful of this as you go around corners, doors and windows. This tends to be where siding installation can go wrong. 
  4. Consider your fastening materials: much like your underlayment, you don’t want to use just any fasteners. Select these materials carefully. Aluminum or galvanized steel will provide a corrosion-resistant fastener for your siding. If you’re using aluminum siding, be sure to use aluminum or stainless fasteners. Nailheads should be a minimum of 5/16 inch in diameter or 7.9mm. Screws should be size #8. Use staples that are no less than 16-gauge. 
  5. Get a vinyl siding blade for your saw: don’t use the same blades as you do for wood. If so, you’ll likely shatter your siding when cutting it. Using the wrong blade can be very dangerous. Blades designed to cut vinyl siding are not very expensive and are readily available at any home improvement store. 
  6. Nail the siding to studs: while not every nail can be attached to studs, be sure that you have several nails that attach to studs. This will ensure a firm attachment to your home as nails in sheathing could adjust as your siding expands and contracts.
  7. Install longer panels around windows first: once you’ve reached a window, continue installing your siding starting with the side of the window that requires the longest panels. Longer panels don’t stretch as easily as shorter ones, which means you’ll have a harder time adjusting these. Just be sure that you’re staying in line with your panels on both sides of the window so that once you reach the top your panels are even to provide a clean look. 
  8. Ensure a panel overlap of at least an inch: each panel of your siding should overlap by at least an inch. But if you’re installing the siding on a particularly hot day, add an extra 3/8 of an inch because your siding is probably expanded over what it normally is.

Allow the Professionals to Do It

FAQs for Vinyl Siding Around Windows

Get answers to common questions about installing vinyl siding around windows. Before starting any project on your home, you should think through the steps and materials required. That way, you’re prepared and know what to expect. Leaving your home without siding for several days while you troubleshoot an issue could leave your home vulnerable to the elements.

We explain some key details to guide your project and ensure success. Read up on these key questions and answers before starting your siding project and before working with vinyl siding undersill trim.

Should Windows Be Installed Before Siding?

If you need to replace both the windows and siding in your home, you should start with the windows. That way, the siding and windows contractor can secure them properly and place the siding around them to create a tight seal to avoid leaks or wind from penetrating your home. 

Sometimes, it isn’t financially feasible to do windows and siding as one project. In that case, your contractor can help you assess which is the more pressing need to protect your home and make recommendations.

Do You Start Siding from the Top or Bottom?

You start siding from the bottom of your home about 1 inch below the top of your foundation. The lower your vinyl siding sits, the more protection it provides for your home from the elements and pests. 

What Is Undersill Trim for Vinyl Siding?

Undersill trim is also known as cellwood vinyl finish trim. When you come to a window or the roofline of your home, it holds the top row of siding in place. You must have this trim piece for your siding job to ensure a good installation.

Can You Install Exterior Window Trim on Vinyl Siding?

Yes, you can add exterior window trim to vinyl siding. To add it to your home, you’ll need to first remove the vinyl siding and J-channel from around your windows. Be cautious throughout this process because you want to keep your siding in good shape as you’ll be putting it back on once you’ve added your window trim.

Allow the Experts to Do It

Instead of managing the siding installation project alone, call in the experts to complete your home’s siding project. Siding is such an important element of protecting your home that you don’t want to risk one seam being exposed or one missing nail. Such a small error could lead to big problems for your home.

2FL Windows, Siding and Roofing offers reliable contractors who will serve as experts for what your home really needs. We aren’t pushy and allow you to stay in control of your home’s project entirely.

Schedule a free siding installation assessment and consultation now to learn more.

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