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Large house with light green siding and white trim

At GS Exterior Experts, we love Hardie Board Siding, and not without good reason. The fiber cement product is extremely durable and the color selection is excellent. But one of the best things about James Hardie products is the Hardie Board window trim (and door trim). Thes Hardietrim boards around the windows look fantastic, really elevating the look of a house from so-so to amazing. 

But how do you install Hardie Board trim around windows? The process isn’t very hard, and the overall cost to the home is relatively small. The fact that something so small, properly installed around windows and doors, can make such a significant difference to a home is remarkable. 

Do You Need Hardie Trim Around Your Windows?

You actually don’t, if that’s the look that you’re going for. James Hardie siding is made so that the siding can run directly up against the window frame, and as long as the frame projects at least 1” out from the wall, this is a perfectly adequate solution. 

If you choose to go with this method then you would just run your lap siding up to the window and then seal it with a caulk gun (using a color-matched caulk).

Why would you run the siding to the window and not use trim? The main reason is cost savings, and is usually done on windows on the side or the rear of the house that are not seen from the curb. At GS Exteriors we discourage this method as, even though it will save a small amount of money, the benefit that you get from installing the trim all the way around is more than worth the price you would pay.

Installing Hardie Trim Around Windows

Installing Hardie trim around windows is quite easy, once you’ve installed the Hardie Board around windows. The products are made together so that the trim and siding installation work together synergistically, without the need for many finishing nails.

The Hardie Trim board is installed with Hardie Tabs, which are an extruded aluminum backplate. The Hardie Tabs are very inexpensive, costing just a few hundred dollars for the entire house. With the tabs installed, only a few finishing nails are needed to secure the trim in place. 

Hardie Trim has many valuable features. Among them are that the trim comes in 12 foot lengths, which reduces waste and speeds up installation, and they have a proprietary back-groove design which makes the product stronger, yet light.

Tools Needed For Installing James Hardie Siding Trim

You will need:

  • Hardie Tabs, which are concealed fastening tabs that come with the trim
  • Pneumatic staple gun with ½” and ¼” staples
  • Pneumatic Finish Nail Gun with 6d siding nails
  • Proper safety gear, including gloves and eye protection

Installing the Hardie Trim

Start by stapling a Hardie Tab and place it on the back side of your pre-cut Hardie Trim board, let it overhang the edge of the trim by one inch. Staple it in place. Then place additional Hardie Tabs every 16” or 24” on-center along the length of the trim, extending one inch out, and stapling them in place.

Take the prepared trim board to the window and hold it in place. If this is a small piece of trim, like the underside of the window, you can probably do this job alone, but if the piece is long you’ll need someone to hold it in place. When the trim is in place, nail into the Hardie Tabs one inch section that is exposed, stapling it to the wall. 

Continue around the window with the remaining trim boards. If necessary because of the window flange, you may need to shim underneath the trim to make sure that it stays flush. Nail it in place.  

Looking for James Hardie siding for your next project? See how GS Exterior Experts can help!


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