Lath and plaster walls are a part of life in an old house. Depending on your situation they can be both beautiful and annoying. Plaster was used for centuries as a wall covering and it wasn’t until the mid-1940s that it began to be replaced in favor of newer and faster option, drywall.
Whether it frustrates or inspires you it’s worth understanding what a plaster wall is and what some of the pros and cons are of this historical wall covering.
Understanding these walls will help you navigate things as diverse as the differences in hanging things on a plaster wall versus drywall, repair and patching techniques, and even WIFI issues and potential resolutions!
Anatomy of Plaster Walls
Plaster walls were applied wet by a skilled plasterer using a hawk and trowel. It could take up to a month (or even longer in cold climates) for a plaster wall to cure fully enough to allow for painting which slowed the construction process down.
The plaster was applied over traditional wood lath which was nailed horizontally to the studs leaving small 1/4″ gaps between each strip of wood. This gap would allow the plaster to push through and form a “key” that once dry would hold the plaster securely to the wall.
There were other forms of lath popular in later years like metal lath which is still used today as a base for stucco applications and rock lath was a predecessor to drywall. Rock lath, popular in the historical cusp years of of the 1940s and 1950s were 2×8 sheets of early drywall that were nailed to the studs and then the plaster was applied over top of it.
Traditionally plaster walls were applied in three successive coats. The first was the scratch coat which was a rough mixture of lime, sand, and water applied to the lath about 1/4 to 3/8″ thick and scratched with hand tools to provide a good bond for the second coat called the brown coat.
Once the scratch coat was dry the brown coat was applied in much the same way by troweling about 1/4 to 3/8″ thick and left to cure. The third, and final coat, which was sometimes skipped in lower end projects was called the skim or finish coat and unlike the first two coats it was applied to a thickness of only 1/8″ or so.
The skim coat was originally lime and water only and beginning in the early 20th century gypsum was not uncommon to use for the skim coat because it would cure so much faster than lime plasters.
The Pros of Plaster Walls
You may be surprised but there are quite a few pros of plaster walls, more than most people expect. These pros certainly make keeping your plaster walls a good idea if they are in decent shape or repairing them rather than tearing them out and replacing with drywall.
Benefit #1 Plaster is Stronger
The tensile strength of a solid plaster wall compared to drywall is signifigant. Just try sanding cured plaster or punching a hole in a plaster wall compared to drywall. Not gonna happen. This strength comes in handy to avoid the dings, nicks, and dents that come along with drywall.
Benefit #2 Plaster is Energy Efficient
Why is a thicker wall better? Lots of reasons, but one of the biggest is energy efficiency. At 7/8″ thick a traditional plaster wall is nearly twice as thick as most drywall applications. Thicker plaster walls provide better thermal breaks than drywall and that saves money on utilities.
Benefit #3 Better Sound Blocking
Plaster is harder and thicker than drywall and because of that and its chemical makeup it is better at sound attenuation. It goes without saying that a wall that is twice as thick should have at least twice as good sound blocking abilities. Great for privacy, bad for eaves-dropping.
The Cons of Plaster Walls
Nothing’s perfect and neither are plaster walls. The benefits I mentioned above are not without their drawbacks so it’s only fair to show both sides of the coin.
Con #1 Poor WIFI Signals
Those thick plaster walls are the places where WIFI and cellular signals go to die. A basic wireless router will likely not cut the mustard in even a small bungalow with plaster walls. You’ll need to upgrade to a mesh system like Google WIFI which is what I’ve used with good results in my 1920’s home in order to get adequate service in a plaster walled home.
Con #2 Plaster Cracks
As it gets older, plaster is continually curing harder and harder which makes it more brittle than drywall. In high traffic areas or in areas with unstable foundations cracks are common in walls and especially ceilings which can be devastated by age and gravity. The effects of gravity on a plaster ceiling can cause more issues because the keys don’t work as effectively as they do on walls, and foot traffic from upstairs can also serve to weaken the plaster ceiling.
Con #3 Harder to Hang Things
The previous benefit of plaster being stronger also means it’s harder to nail or drill into which makes decorating more difficult. There are some tricks that will help you hang things on a plaster wall in this previous post. Just know that putting a simple nail in the wall may be a fruitless pursuit if you have plaster walls.
In my honest opinion when you do the math it’s worth keeping your plaster walls if you have them, but if they’ve already been replaced you’ll be just fine too. I certainly believe that replacing plaster walls is one of the worst mistakes of historic homeowners due to the mess and expense it creates. If you’ve got plaster enjoy the benefits and bear with the challenges because you’ve got a historic wall that is only found in very high end houses today due to the immense skill and cost it takes to have plaster walls.
I’m sure you have your own opinions as to the pros and cons of plaster walls so let me hear your thoughts in the comments below. What did I leave out?
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I love old houses, working with my hands, and teaching others the excitment of doing it yourself! Everything is teachable if you only give it the chance.
One of the early marketing claims for drywall was that it was a better insulator than plaster, perhaps because it usually has some air blown into the mixture as it’s made. Then again, plaster that has suffered a little delamination over the years will have the insulating properties of all those air pockets on its side, which also helps block noise transmission. But it’s probably overly optimistic to assume that either plaster or drywall will contribute more than a trivial amount of insulation by themselves; filling the cavities usually makes the biggest difference. A couple I know just had one of their plaster walls ripped out and replaced with drywall. They also had all the “old fashioned” cellulose insulation, which was packed so tight that it looked like brown concrete, replaced with modern fiberglass batts. I have my doubts as to whether that was the wisest choice they ever made. Batts are almost impossible to fit to an imperfect wall cavity, with gaps almost inevitable forming around electrical boxes, cables and pipes. And those gaps allow air currents that can devastate the effectiveness of the insulation; something which becomes obvious with the cold spots that form on the coldest days of the year. I can understand their frustration in dealing with walls that are kind of a mess and the allure of perfectly flat new drywall. But if I owned a house like that, I’d be stabilizing and skim coating the plaster. Yes, by using fire rated panels and/or multiple layers and doing a better-than-average job of mudding or skimming, you can get most of the desireable characteristics of plaster from drywall, but if you already have them, why re-invent the wheel? And how confident can you be that the contractor you hire will know or care enough to replicate everything good about your old house, including the solidity of its “old fashioned” tightly packed insulation.
It’s nice that you mentioned how thicker plaster walls could provide better thermal breaks than drywall and that would save money on utilities. We just bought a very old house and we are planning to renovate it now. But before we do that, we need to get some building supplies first, like plaster for example.
i have a craftsman home built in 1912. The lath and plaster walls are in great shape. The texture is a little heavy for my taste but I’m learning to live with it as I don’t want to do anything to undermine the plaster’s integrity. Also, there are 5 bedrooms between 2 floors and once you close a door, you can’t hear a thing.
I had 6 feet of insulation blown into the attic last year but there’s no insulation in the walls. What would be the best way to add insulation to the outside walls without tearing the shake siding or opening up interior walls? I’m on a very tight budget and doing most of the work myself. Any ideas or suggestions?
If there were previous renovations done to removed the plaster walls and replace with drywall, would you suggest having someone come in to plaster them? Is it possible? Would it help with the authenticity of a historically-responsible remodel?
I wouldn’t go back to plaster unless you lots of money to spend. You could have a veneer plaster applied over it to make it look more historic. It’s a much more affordable option.
We have plaster on the first floor and drywall upstairs (converted attic space). I would not have believed the difference plaster makes in sound transmission if I hadn’t lived in this house and been able to hear it as I moved from one floor to another. The upstairs has insulated walls (fiberglass batts) while the plaster walls are uninsulated, but the downstairs is still much, much quieter.
It would be nice to hang things without worrying about cracks, but it’s a small inconvenience and a good excuse to minimize clutter.
The other great thing about plaster is the it won’t mold. Unlike drywall, which has a paper coating, plaster has no such issue. So if you purchase an old leaky house that has plaster walls (and ceilings) do not fret. You will not have a mold issue. Also if you use Big Wally’s Plaster Repair.. you can fix almost any damaged wall if there is still plaster clinging to it. In fact the worse shape that plaster is, the better Big Wally’s works. (Because the gap between the plaster and the lathe will be large enough to hold a lot of the Big Wally’s goopy stuff
What about insulation? Up north they want add blow in insulation between the lath and exterior walls? Wouldn’t it be better to wrap your house? Or should it be left as built?
We needed to replace our exterior siding, due to hail damage. After removing our old siding, I installed extra electrical in every room and had closed cell foam sprayed between the studs. The house is even more quiet, stronger, and we are saving approximately 33% on our energy costs. We love the character of our 105 yr home and are very happy to have the plaster through out the home.
We needed to replace our exterior siding, due to hail damage. After removing our old siding, I installed extra electrical in every room and had closed cell foam sprayed between the studs. The house is even more quiet, stronger, and we are saving approximately 33% on our energy costs. We love the character of our 105 yr home and are very happy to have the plaster through out the home.
I have used Big Wally’s and the stuff really works great. I think it’s the best way to save a wall with very little mess.