“Sub-baseboard” Should I keep it?
I’m not really sure what to call this, but my old lathe and plaster walls had 1x4s all along the bottom. This was behind the molded baseboard and didn’t have plaster over it. That means there’s also a gap between the edge of the finish floor and the wall. All the resources I find talk about the molded decorative baseboard and I’m having trouble finding anything that mentions anything like this (if someone just knows what this is called, that might be enough to help me answer my question). At 3/4″ thick, it was about flush with the plaster above. I tore out the lathe and plaster in my kitchen and will be replacing it with drywall. I took out most of the 1×4 boards because they were in the way for one reason or another. Should I put those back, remove the rest, replace them with 5/8″ plywood (to match the thickness of the drywall), fill in the edges of the finish floor with 3/4″ plywood, or something else? Most of this is going to be behind kitchen cabinets. I also see some places recommending installing baseboard behind the cabinets and appliances even if it won’t be visible. One part of the rationale is that it helps with air sealing (and critter-sealing). Would having this non-aesthetic sub-baseboard be an alternative to that? It does seem like it might be easier to get a good air seal between a board and drywall than between the floor and drywall. But with the gaps at the edges of the finish floor, it would also be pretty easy to caulk or foam along the bottom of the drywall. There are going to be a few places where the lathe and plaster wall joins new drywall, which will be shimmed out or just have a bump in the wall. Not sure whether those should be treated any differently. I’m in climate zone 4C, on the off-chance that matters.
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> I’m having trouble finding anything that mentions anything like this (if someone just knows what this is called, that might be enough to help me answer my question).
It's likely a screed board. It provides a reference surface for the finished plaster wall to work off of, similar to the window frames in a room. It also conveniently is a good surface to attach the baseboard to.
There is no reason to replace this or substitute it with 5/8" material if you are installing drywall.
As far as critter sealing, if you're relying on interior finished surfaces to keep out vermin, you have bigger problems.
As far as air sealing, you have to determine what your air barrier plane is. If it's drywall, then yes, it's a good idea to seal the drywall, by that would often be done to the bottom plate. (Again, it depends on what the plane of your air barrier is.)
Lastly, putting baseboard behind kitchen cabinets is a waste of money and wouldn't work with most cabinets as the back is intended to be tight to the wall from top to bottom.
Thanks Patrick, that's super helpful and matches my suspicions. I was just apprehensive about removing something when I didn't know what it was or why it was there in the first place. Searching for "screed board" isn't giving me much better results (seems to be mostly stuff about concrete and using a board as a tool for leveling), but your explanation makes sense.
My primary air barrier (such as it is) will indeed be the drywall, so I will make sure it gets sealed at the bottom.
My cabinets are going to be on adjustable feet, so I think the baseboard wouldn't cause an issue, but agreed that it seems like a waste of money. I think I may be misremembering and most of the internet people were just advocating for baseboard behind appliances. That still seems unnecessary to me, but more defensible. It's also something I don't need to decide for a while though :-D
Do you think there's any issue with that 1" gap at the edge of the finished floor? I guess after drywall it will go down to 3/8". Behind the cabinets that should be fine (as they're on feet, they don't need to be supported at the very back). There are a few places where it will be at the edge of visible floor, but hopefully that's small enough to cover with baseboard.
There's one place where I need to put drywall at the last two feet or so of a wall that is lathe and plaster. I think I may put back the screed board there to provide a reference for shimming out the drywall and a consistent backing for installing baseboard. WDYT?