from The Craftsmen Blog 
The walls of many pre-war houses are most likely wood lath, like in the picture below, 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 called 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All too often we see historic houses gutted to the studs to install new drywall to replace the “outdated” plaster.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!
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 website.