GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Vertical siding window trim detail

connorkatz | Posted in Energy Efficiency and Durability on

Question about window trim details with vertical siding – in this case Hardie panel board and batten.

Typically when vertical siding is installed it gets put tight up against the window on all sides, then the trim goes over that around the window.

Thinking years(decades) down the road, if you ever need to replace a window (and want to use a nailfin window, not some crappy replacement window) you have to cut back the siding to get at the nailfin to remove the window.

I am wondering if anyone has installed vertical siding, keeping it short of the window by a couple inches and then rabbeting the back of the trim so it butts up to the window and covers the vertical siding by an 1″-1.5″ 

So for example w 5/16″ Hardie panel you would use 5/4 trim  and route out 5/16″ deep 1-1.5″ in on the window trim(probably LP or something, no one wants to dado or route out Hardie)

That way if you remove just the trim you have direct access to the nailfin to remove the window, similarly to how you would when installing horizontal lap siding.

Cant think of any reason why this wouldn’t work, just wondering if anyone has any thoughts?


GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member


    Sounds like a good detail. Another alternative if you want to apply the trim over the Hardi-board (as the battens are) would be to keep the siding back off the flange, add a piece of slightly thinner material to fill the gap, caulk the joint, and install the trim.

    This is a lot easier if you have a rain-screen cavity. As long as you keep the furring strips back off the flange, you can leave the siding tight to the window, as it will be easy to cut back later if window replacement is necessary.

  2. andy_ | | #2

    The two methods described, trim over the siding and trim butting the siding are done that way because of the materials and the tolerances in cutting them. Shingles and lap siding can easily be cut to fit up against the trim, but the trim would be difficult to scribe to go over the shingles.
    Big boards that butt up to the trim for B&B are possible, but it's easier to have a little wiggle room around the window on those boards and just cover them up with the (now thinner and cheaper) trim. Board and batten with Hardie is usually big 4x8 sheets with "battens" tacked on mostly for decorative purposes.
    In the unlikely event that you'd be replacing entire window units, I'd be inclined to use the trim as a guide and cut right through the board and replace with a deeper trim piece once the window was replaced. Basically, there's a way to do that down the road that doesn't change the initial install method. Either way, I'd be much more concerned with flashing and water drainage details today than with a possible repair method decades from now.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |