I own an older home in central PA; my guess it is pre-1920's and I was going to remodel the living room and insulate the walls and run new wiring. The walls are horse hair plaster; when I removed the plaster and lath there are planks that run horizontally on all the walls.

If I remove them to insulate do I need to put them back on? Are they part of the structural framing?

  • 3
    Where are these horizontal planks? Are they horizontal pieces between two vertical studs? Or are they behind where the wall surface would be? Apr 29, 2011 at 14:49
  • 1
    A photo would be useful (if you can)
    – ChrisF
    Apr 29, 2011 at 19:00
  • The planks could look nice...maybe keep them and reuse as the finished wall? Back then it was cheaper/easier to put planks up in 'lesser' rooms than to have them fully plastered. My hunch is that they were originally plank walls and later 'upgraded' to full plaster. As long as the exterior of the walls has sheathing of some sort or cross-bracing, the interior planks are likely not structural (disclaimer: I'm not an engineer!)
    – DA01
    Apr 29, 2011 at 20:29
  • the planks are on top of the studs some span over 3 studs over are 5 and 6 studs
    – dave
    Apr 30, 2011 at 19:42

3 Answers 3


Most likely it is shiplap. We just remodeled our kitchen in our 1935 house and underneath the drywall and paperboard, we had something similar. Actually the order was: shiplap, cheesecloth, several layers of wallpaper, then either paperboard (lower half) or drywall (upper half).

As far as whether or not it is structural, we went with the assumption that it was. I'm sure the vertical spacing of the studs in approach does not meet current building standards. However, I am not an architect either. At the very least, having it behind the drywall makes it incredibly easy to hang the drywall and anything else for that matter.


My house was built in several stage starting in the late 1800s. Throughout most of the house, the shiplap was nailed to the outside of the exterior walls and the inside was lath and plaster. In the stairwell to the basement, which runs along an outside wall, the shiplap is attached to the inside of the exterior wall and the outside only has the thinner wood siding.

I doubt that the purpose for the shiplap was primarily structural, but since there were no 2x4 braces in the corners of my walls and the walls are all still very plumb and square, I suspect it does provide some lateral stability.

You might want to consider blowing paper insulation into your exterior walls. It would only require you to remove the top-most shiplap board and reduce your risk of disturbing the lateral stability if you remove all the boards. Do you know what's under the exterior siding in your house?

One other thing to consider: If you do decide to remove all the shiplap, you may have to drill pilot holes when nailing then back up. It's not uncommon for older homes to have hardwood studs, and today's framing nails bend easily when hammered into old hardwood.


I have shiplap as well, in our circa-1910 home.

Yes, it is structural.

And if it's like ours, they are actually in a tongue-and-groove configuration, which makes them extremely difficult to remove without destroying them.

You can safely remove a run near the top and bottom to install insulation, new wiring, etc., but I definitely would not recommend removing them all.

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