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.