Plaster is one of my favorite features in an old house and one that is easily overlooked. After all, how much do you really notice a wall or ceiling unless something is wrong with it. That being said, I think I can convince you to keep your plaster.
You may notice cracks in you old plaster and gouges from years of hanging pictures and knick-knacks, but that doesn’t mean it’s toast. Did you know that lime plaster can even heal its own small cracks over time? We’ll talk more about that below, but for now, don’t feel like that old plaster’s done just because it’s old.
There are a lot of reasons to keep original plaster and below are the six biggest reasons in my mind why saving old plaster is a worthwhile goal.
1. Plaster is Harder Than Drywall
If you put plaster and drywall head to head, there is no competition which is a harder wall covering. Traditional lime plaster has been slowly transforming itself back into limestone since the day it was applied. Traditional plaster walls are about 7/8″ thick compared to standard drywall which is 3/8″ gypsum plus a piece of paper on either side for a grand total of 1/2″.
That means a lime plaster wall would be nearly twice as thick as drywall and made of limestone! Which do you think is better at resisting dents and dings?
2. Plaster is a Better Insulator Than Drywall
We’ve just finished talking about plaster’s thickness so it naturally follows that the thicker the wall, the better the insulation it provides. Yes, your plaster walls likely have little to no insulation behind them, but the wall covering itself has an R-value twice that of drywall.
Being that 1/2″ drywall has an R-value of .45, there isn’t much to gain here, but every little bit helps, especially when the plaster is already there. Why remove it for something inferior?
3. Plaster is a Better Sound Blocker Than Drywall
Nobody likes a noisy house, and plaster is extremely helpful when it comes to reducing noise through walls. STC (Sound Transmission Class) is a rating for various wall assemblies used by the building industry. It’s helpful in comparing different ways of building and how they affect the amount of sound that transfers through a wall or ceiling.
1/2″ drywall on 2×4 wood studs has an STC rating of 34 according to National Gypsum. Compare that to a nearly 1″ thick lath and plaster wall which would have an STC rating of approximately 52 according to US Gypsum. That’s an increase in sound blocking of 52%. Not bad for an old wall!
4. Plaster Can Self-Heal Cracks
It’s not a miracle, it’s just science. Lime plaster goes through a curing process called carbonation which causes it to continuously be building and rebuilding bonds between its particles. No, it won’t heal big structural cracks, but small hairline cracks can heal themselves over time and I have seen it happen on more than one occasion. So, don’t count it out.
5. Plaster Removes Carbon Dioxide From the Air
I don’t know if it’s coincidence that as we have used less lime plaster and mortar in construction, the atmospheric concentration of carbon dioxide has continued to rise. I’m sure increased pollution and population growth have played a role too, but that doesn’t mean lime didn’t help.
Lime, the primary ingredient in plaster and mortar prior to the 1930s, releases water and draws in carbon dioxide as it cures. That process of carbonation we talked about earlier. It needs the carbon dioxide to help it turn back into limestone and so it continuously pulls carbon dioxide from the atmosphere little by little, as long as it is standing.
Sadly, gypsum plaster doesn’t do the same thing. To me, that makes lime plaster and mortar some of the greenest building materials ever invented. If that alone doesn’t convince you to keep your plaster, I’m not sure what will.
6. Plaster Lasts Longer Than Drywall
When you combine all these things together, you get a longer lasting and over all better product in plaster that has and will continue to stand the test of time. It’s no fun to replace walls and a lime plaster wall will need replacing less often than drywall, due to damage and age.
Even if the plaster is sagging or cracked, it can be repaired to last for decades more. I’ve found that the reason most plaster is removed is because of homeowners and contractors simply not knowing it could be retained or repaired.
Put all that together and you’ve got a harder, more insulating, better sound blocking, greener and longer lasting wall covering that can be repaired. When you look at it that way why would you ever replace your plaster walls? I dare you…keep your plaster.