5 Worst Mistakes of Historic Homeowners (Part 4 Plaster)

The walls of any pre-war house are most likely wood lath like in this picture covered with 3 coats of plaster. The work took a long time and was very labor intensive. Not to mention it required a skilled plasterer to make sure the plaster was properly applied and the wall was smooth and level.

Then when the GIs returned home from WWII the baby (and housing) boom hit America, and there was a huge demand for quick affordable housing. A new product was just beginning to get some traction in the wall covering business call gypsum board or sheet rock. It was a wall that could be screwed or nailed to the studs by a relatively unskilled laborer at close to twice the speed and half the cost of the traditional 3-coat system. And since this wall wasn’t applied wet like plaster it could be painted right away and thus got the nickname “drywall.”

A traditional 3-coat plaster is typically 7/8″ thick and when you add in the 1/4″ wood lath that supports the plaster wall you have a wall that is more than 1″ thick! Compared to today’s most common drywall thickness of only 1/2″, that is a difference worth noting.

Today the cost of a full 3-coat plaster wall is still expensive and timely to install, but when you live in an old house with one already installed you should try to reap the benefits of someone else’s labor all those years ago.

All to often we see historic houses gutted to the studs to install new drywall to replace the “outdated” plaster. Sometimes the plaster has been neglected past the point of no return, but most times it can be repaired. Usually it’s torn out in the name of insulating the wall cavities. But as with anything in the building trades, there is more than one way to skin a cat! In order to save folks the mess and expense of tearing out their walls we recommend removing a few clapboards on the exterior in order to insulate the house to modern standards. Remember, historic homes typically have no plywood sheathing under the siding so insulating with this method is just as effective plus it’s faster, cleaner, and much cheaper!

The Benefits

Here’s just a few of the benefits of having a real plaster wall to consider before you think about removing yours.

  1. Thicker walls mean better sound dampening.
  2. Thicker walls mean double the R-value of ordinary drywall.
  3. Wood lath serves to strengthen the wall by adding additional racking resistance.
  4. Plaster increases the historical authenticity and therefore resale value of a historic home.
  5. It’s already there! It’s always “greener” and cheaper to retain existing elements.

Hopefully, this has given you some things to think about when it comes to your plaster walls. If you’d like to read more about repairing and maintaining your historic home’s walls check out our video post How To: Repair Plaster Walls or our other post How To: Repair Old Plaster.

Read the rest of the 5 Worst Mistakes of Historic Homeowners:

Part 1 Windows

Part 2 Floors

Part 3 Siding

Part 5 The Details


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by Scott Sidler

Scott is the owner of Austin Home Restorations, a company that specializes in renovating and restoring historic homes in Orlando, FL and the creator of The Craftsman Blog. When not working on, teaching about or writing about old houses he spends time fixing up his own old bungalow with his wife Delores and son Charley.



  1. Kim on said:

    In my Chicago 1920s condo, we have drywall OVER lathe and plaster, a truly unholy marriage! So hard to get anything properly fastened in the walls.

  2. Yes! Plaster, all the way! My husband thought I’d lost my mind. To him, the best thing to do was rip off the old 70s paneling (gross!) and then hang drywall OVER the plaster! I nearly fainted.

    There are a couple rooms in this house where the plaster was apparently a bad mix. The scratch coat, which can be seen around some of our old door moldings, had reverted back to mostly sand and horsehair. One touch sent it crumbling.

    Not to be dismayed, I fought for the plaster. Since I do about 98.9% of the labor around here, I won that argument. That happens a lot! He buys, and I work. Seems fair.

    The first room was the master bedroom. There were areas popping loose from the lath because they keys were broken. Not shocking, since they’d nailed furring strips and paneling over it. In all areas besides the crumbling ones, I screwed the plaster back to the lath with plaster screws and washers, skimmed it with hot mud and fiberglass mesh, then skimmed it again. Hot mud wasn’t my first choice, but it worked really well. I’ve never mixed plaster, and I didn’t want to take a chance on my walls.

    The fiberglass (A trick I learned from This Old House) worked brilliantly for strengthening the cracks. Five years later, and those walls are still beautiful. The hot mud and a wide mud knife left a nice sheen to the walls that looks for all the world like the surface is plaster. It took a while to get a feel for the technique, and it’s a bit labor-intensive, but there’s no way I would hang drywall anywhere that I had a choice.

  3. Elise on said:

    Howdy just wanted to give you a quick heads up. The text in your content seem to be running off the screen in Safari.

    I’m not sure if this is a formatting issue or something to do with web browser compatibility but I thought I’d post to let you
    know. The layout look great though! Hope you get the problem fixed soon.
    Many thanks

    • Thanks Elise. Editing and formatting is a full time job it seems. ;-) I appreciate the heads up!

  4. John Townsend on said:

    In the first place the difference in R- value between plaster/lath and drywall is nearly insignificant with respect to the TOTAL R value of the wall itself, assuming there is insulation. There is also only a minor difference in soundproofing. In the second place drywall over plaster utilizing 2 1/2 screws into the joists is a very practical idea for ceilings. Notice I said ceilings but NOT walls. Care to have that plaster dropping down on your head from time to time as it degrades over time? How about getting up there to rip out that ceiling plaster so as to either replaster it or drywall it? You can repair the plaster or replaster but there is no advantage save EXCEPT from a purists’ historical standpoint. Other than that there is absolutely NO ADVANTAGE in plaster on the ceilings. I hung drywall over plaster on the ceilings in our 1935 Craftsman bungalow. The only drywall on the walls is in a couple of places where the plaster had come loose Patching as it were. Other than that the walls are original.

    • matt on said:

      re: drywall patches on your plaster walls…as carol describes above, you can repair broken plaster keys with plaster screws and skim coats.

  5. Bethany on said:

    I wish I could have kept my old walls. Too bad previous owners nearly destroyed it!

    If you have a historical home.. an old home. Do what ever you want. Anything! But whatever you do I hope that it’s good for the home so that it WILL out last the current crop of new homes with built w/ oriented strand, chip board, MDF crap et al. …

  6. Connie on said:

    We have 2 homes in Galveston Tx circa 1884 & 1887. Both are baloon framed houses and after much research an convinced that filling them with insulation could put the structure at risk for moisture damage. The walls were designed to breath and the plaster to insulate. One problem some walls had to be removed to re plumb & re wire (permitted) and we’re faced with several problems. 1, most all plaster and lath is furred out before the laths are applied adding to the depth deficit in replacing the wall. 2 , the insulating qualities of that thick P&L is gone and lastly , replacing the wall so it finishes out to the same depth as the previous wall so your window & door trims reinstall at the same depth.
    Out depth from bare stud to door & trim casings is 1-1/2″ thick . The solution from INSIDE the wall 1st 4′x8′ T&G XPS , then 7/8″ drywall on top. We finish out at the exact same depth as the old wall, create a barrier of insulation on the exterior walls while leaving the framing open to breath. I contacted Dow Chemical in Midland Michigan, they were incredible in running the norms based on our zip code and making recommendations to us on what to use…………hope this helps others in the same quandary

  7. Connie on said:

    One note to the comment above concerning replacing drywall where plaster and lath was removed………… If the wall has doors or windows it’s likely you’ll need to fur it out . Even if you’ve been lucky enough to remove the door & Window trims without damaging them ( we left ours in place) the jamb thickness is going to dictate where those trims need to be. Most of our Jambs are at 6″ width. You can fur out the trim but the profile looks ” off ” next to the wall and base trims………. tried that first……… Rip out, redo

  8. PCL on said:

    I think John Townsend has the right idea. Do each wall and ceiling on a case-by-case basis, with an aim of preserving as much as possible. There is nothing wrong with using plaster screws and glue injection to stabilize a plaster wall, if it holds together when it’s done. But there’s also nothing wrong with drywalling over a problem wall, if all the door and window frames are shimmed to match the new wall thickness. Drywalling over a plaster ceiling is a great way of making it safe, especially with mid-century “transition” (rock-lathe or expanded mesh) ceilings that tend to collapse catastrophically and can be quite dangerous. And if you really have to get into a wall (insulation can be blown, piped or even stuffed through holes, but dangerous wiring can require much more demolition), it’s no big sin to replace the plaster on that wall with drywall; you can even use 5/8″ or even 1″ (usually double 1/2″ layers) to replicate the solid feel of plaster. If you do a good enough job of either resurfacing plaster or taping/mudding drywall, it will be impossible to see which walls are which.

  9. Chris on said:

    I couldn’t find a reasonably priced plaster contractor, so I put up drywall. The house was a rental property (a lot of holes) and the walls were significantly damaged by cellulose being blown into the wall cavity. The insulation settled and coupled with poor maintenance and rainwater management, I ended up with a soggy-mess of a wall. It can be hard to tell a wall is a damaged behind so many layers of paint (I missed it during inspection).

    My question is how should I go about replicating a plaster finish on the drywall? Slightly uneven skim coat and sand? Any recommendations would be greatly appreciated.

    • Chris, I like a modern plaster finish on top of drywall to get the look of old plaster walls. We use a 50/50 mix of veneer plaster and pre-mixed joint compound. You need both in order to have it hold properly on regular drywall.
      Mix them together and apply like you would a veneer plaster finish. Trowel it on and knock down the high points after it sets up. You can add sand to the mix if you would like the added texture. It’s hard to describe the whole process in a comment. I plan to put together a video soon to teach how the process works.

  10. Smitty on said:

    Question instead of comment. I have gone all the routes described above in many rooms of our 1832 Greek Revival, but am at an impass in a northeast facing bedroom. The outside walls seem to be more sand than plaster and will never stand a coat of paint. The interior walls are already down to the lath due to great variations in plaster depth which made repair next to impossible. I will use 5/8′ drywall and should get a good reveal at the two doors.The outside walls do not demonstrate the breaking of keys as did the partition walls. Maybe because the interior walls flex more easily. I would like to avoid removing the plaster from those two outside walls and just skim a veneer over them when I do the rest of the drywall.

    Now the question. Is there a difference in the type of plaster used on the exterior walls as opposed to the partition walls? Is there any vapor barrier behind the plaster on the exterior walls? Would it be worthwhile to tear the old plaster down and install a vapor barrier then drywall as the other two walls?

    I am taking a two day break from this project, so replies can be well thought out and critical. I will get over anything you beat me up on!



    • Ed, the plaster should be the same composition and thickness on the entire interior of the house. Due to the age of the house there won’t be a vapor barrier, but you can definitely add one if you’d like. It’s not quite as effective obviously unless it completely encompasses the house. We use a veneer plaster over top the 5/8″ drywall to help it blend in better with the existing walls. And if you have a sanded finish which it sounds like you might then you can always just add simply play sand to your plaster mix.
      Personally, I would try to save as much of the original plaster as possible, but you’ll have to decided what is reasonable considering the current condition of the walls.

  11. Oma on said:

    Love this article. We are considering buying a home with plaster walls. They look solid, but have some mildew stains. First thought was rip out walls, install insulation and drywall. But after checking out this article and the one on vinyl siding (which is on this home), I wonder what the problem really is and how to fix it. I hate damp walls and mildew.

    • Oma on said:

      Forgot to mention, the house is from the early 1800s. Also worried about lead and asbestos.

      • Make sure you hire a EPA certified firm to do any repairs on the house so you and your family are protected from lead. As for asbestos there is no way to tell without testing . But asbestos wasn’t used in the US until the late 1800′s.

    • Oma, a good HVAC system and possibly dehumidifier will do wonders to hep with your mildew problem. Mildew will grow on drywall just like it would plaster so go for the source of the problem not just the symptoms. If you have moisture issues it might be the vinyl siding trapping vapor, a leaky roof or siding, leaking pipes, or any number of things. Somehow moisture is getting in and it can’t escape. That’s the problem to solve. Good luck with the house!

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