How To Install Hardie Siding Around Windows

Kirstin Harrington
by Kirstin Harrington

If you’ve wanted to spruce up the exterior of your home, adding James Hardie siding is a great way to do so. It can make your house look new, and thankfully, the installation is rather easy. Just like any other siding, it’s available in a variety of beautiful finishes that will fit your preferences.

It’s important to install siding correctly, especially around windows and doors. If you’re a beginner, it can be tricky, but you’re in luck. The simplistic way of putting it would be cutting the proper size siding piece and nailing it to the exterior wall.

Installing siding properly can save you stress, time, and money during a home improvement project like this. Hardie siding is durable and will last for decades if you follow the directions below.

Do You Need Siding Installation or Repair?

Get free, zero-commitment quotes from pro contractors near you.

Get Everything You Need

Before you start tearing off the old siding and replacing it with the new stuff, it’s important that you have everything you need. Read the related materials that come with the siding in case you have to pick up anything from the hardware store. Some of the more commonly required tools are:

  • Stapler
  • Drill bit set
  • Air compressor
  • Hammer
  • Jigsaw
  • Safety goggles
  • Sawhorses
  • Cordless drill
  • Chalk line
  • Caulk gun
  • Dust protection mask
  • Kick-out flashing
  • Trim nailer
  • Siding nail gun
  • Siding gauge
  • Speed square 
  • Level 
  • Air hose
  • Fiber cement siding blocks
  • Stainless steel nails
  • Mounting blocks

This may seem like a lot, but you may own the majority of this list already. Have everything out and lined up when you’re ready to begin. This will save you time and hassle, so you’re not in the middle of the project scouring for a tool.

Following Safety Measures

Not all types of siding and trim require safety gear, but Hardie does. You’ll want to make sure your eyes are protected with glasses or goggles. This is essential when cutting or nailing the siding panels.

You’ll also want to use an N95 mask while cutting the panels as well. There can be excess dust and debris flying around. Wearing one will prevent you from inhaling anything dangerous.

Lastly, consider using ear protection. When you’re using a circular saw during this project, it can create an intense, loud noise. Taking the extra step to protect yourself with these three things is a great way to practice safety measures.

Make a Detailed Plan

Something else you’ll want to do before getting started is to make a detailed plan. Applying siding around windows can be complicated, but with a proper plan in place, it will be much easier. Write down how many windows your home has and jot down the dimensions of each one.

Then, pick out how many windows you’ll be installing the sidings around. Factor in how much square foot area of siding you’ll need per window. Ask yourself whether or not you plan on painting the siding after it’s installed as well.

When you feel confident in your plan, you can move forward towards getting the project done.

Detailed Instructions for Installing Hardie Siding Around Windows

This is the ultimate guide for installing Hardie siding around your windows. You don’t need any special skills to take on this home renovation project.

Step One: Removing Existing Trim

The first step isn’t necessary for all homeowners. By no means do you have to remove your old trim, but in the event you do, I wanted to include it. Take a razor knife and cut from the edge of the trim where it meets the wall.

If you don’t start there, it could strip away caulking and paint. Cut all the way around the window using that method. Eventually, you’ll make a gap that you’ll pry up with a pry bar. Do this carefully to avoid cracking at the junctions where nails meet.

You can then take a putty knife and pull the nails out of the wall. Make sure you put these in a container to ensure no nails are loose in your yard.

Step Two: Measuring the Trim Around Windows

Once you’ve completed the first step, all of your old trim should be off the windows. It’s essential that there aren’t any nails sticking out. If there are any you can’t remove, take a hammer to level up the nail heads that are leftover.

Now, measure the window to get an accurate number for the size of the trim you’ll need. Take a measuring tape and pencil to double-check that the measurements are correct.

Step Three: Cutting Hardie Trim Boards

Take the measurements you wrote down from step two and get ready to cut some Hardie trim boards. Remember to wear your safety gear for this step, especially a mask and goggles. If your saw is loud, it’s suggested to wear ear protection as well.

Next, cut the trim boards using a conventional saw. It’s best to use fiber cement blades that are designed for cutting trim boards. These blades have fewer teeth and offer a faster cut with less of a mess.

Take a speed square or layout square to place on the measured lines. Using the saw or power shear, cut the boards. If you do decide to use a saw, consider investing in a dust collection bag to make clean-up a breeze.

Step Four: Replacing Wood Sill with Hardie Trim

In the event that you find rotten wood sills while doing this project, I wanted to share with you how to replace them. You can use an angle grinder to get the perfect sized piece of trim. After you’ve cut it, snap off the cutting plank section, and you’ll be ready to move forward.

Step Five: Installation of New Hardie Trim Boards

Take a look at the Hardie trim boards before trimming them for your windows. Make sure there aren’t any touch-ups needed. Face-nail trims with two-inch 16-gauge finish nails about every 16 inches.

This makes the trims lay flat, especially when you ensure that a drip cap is installed over the window. It’s important to leave a ¼-inch gap between the plank and the window itself. This lets any liquid go behind the siding to get out and prevents things like mold and mildew.

Then, the top post will be put across the two vertical blocks and extend to the bottom sides of the trim. After this, you can install shims to make the wall even with the window flange. Repeat this step for each window you’re adding the siding around.

Step Six: Sealing the Seams

The sixth step isn’t necessary for everything, but it gives a flawless finish to the entire project. Take a caulking gun and seal the seams around the window. The best way to do this is to cut the caulk tube nozzle very close to the tip.

This allows you to easily get into small openings and fill things like the joints. Wipe it down to have a clean finish, and be sure to caulk at a 45-degree angle. Lift away in a fast motion after a single pass to get even results.

Step Seven: Proper Window Flashing

Now that you’ve installed the Hardie siding around your windows, you’ll want to make sure they’re flashed properly. This helps rain to stay out of your house and acts as a weather-repellent. When adding the flashing, do so in horizontal and vertical directions to give the most thorough protection you can.

Step Eight: Finishing the Job

The last thing that you’ll want to do is paint the trim. While Hardie does come with a 15-year warranting, fading is found to happen. You can paint before you install the siding or after.

Do You Need Siding Installation or Repair?

Get free, zero-commitment quotes from pro contractors near you.

Related Questions

Can you hang things on Hardie board?

Hardie board is known for being extremely durable. It’s tough and can hold lightweight items, like hanging flower baskets, as long as they weigh less than a pound. Anything heavier comes with the risk of damaging the siding. 

How often does a Hardie board need to be painted?

It depends on where you live when it comes to maintaining the Hardie board. The paint could last anywhere from five to 15 years. It’s crucial to apply the paint correctly to get the most long-lasting quality out of it possible. You can do routine maintenance on your siding to ensure that it lasts longer as well. 

Is Hardie Plank better than vinyl siding?

While they’re both very strong, HardiePlank is known for being more durable. If you live somewhere with extreme weather conditions, it’s a better option for you. It requires less upkeep and looks great on any home.

Kirstin Harrington
Kirstin Harrington

Kirstin is a passionate writer who loves helping people learn new things when it comes to home improvement. When she's not behind a keyboard, she enjoys DIY projects, crafts, spending time with her pets, and making videos. She hopes that with all she writes, someone is finding a solution to their home improvement needs.

More by Kirstin Harrington