05/30/2025
When new siding gets complicated—what we found behind the walls…
We’re roughly 1/3 through our latest Hinsdale project where we removed existing panel siding—only to find the original lap siding still underneath. The homeowner was not aware that this was the case before we removed the siding.
This setup raises a common question we get from homeowners: can you install new siding over existing siding? The answer is… sometimes—but only if it’s done the right way.
There are a few potential benefits to installing new siding over old wood-based siding:
- You gain some extra insulation.
- You have more surface area for nailing (though siding should still be fastened to studs wherever possible).
- You can avoid potentially significant additional demo costs and material disposal.
That said, the downsides can be significant if it’s not done with care.
Aligning new siding over old can be tricky—especially if you’re trying to install horizontal lap siding over existing horizontal siding. If the original lap isn’t removed or properly leveled, the new siding won’t sit flat, and the finished result will look warped or uneven, and may not shed water effectively.
We’ve seen homes where different materials were patched in over time, creating uneven protrusions, random gaps, and missing sections—all of which make proper installation a challenge. And if the previous work was rushed or unpermitted (like in this case), it may have just covered up serious issues rather than solving them.
In this project, we encountered all of these issues. The last owner had slapped on panel siding without addressing what was underneath, installed new windows over the old siding without flashing, and just covered large gaps in the structure with siding, leaving gaping holes underneath.
Our solution is a thoughtful mix of:
- Installing batt insulation to fill the large wall gaps and then sheathing over the holes/open sections
- Using rigid foam board to level out protrusions over large areas
- Using ripped strips of foam board as furring strips to even out the old lap siding and create a flat surface for the new siding—so the new siding can be installed cleanly and securely.
It’s more work, no doubt—but it’s the only way to get a clean, long-lasting result without completely removing the old siding (which would have caused issues with the existing windows, since the have nail fins that were installed over the old siding).
Moral of the story? Choose an experienced and adaptable exterior remodeling team that knows how to handle these types of unknowns in the right way. A big part of construction (remodeling specifically) is problem-solving, and you want to team that can do so effectively.
Photos below show some of what we uncovered.
