6 Reasons to Keep Your Plaster

By Scott Sidler January 16, 2017

6 reasons to keep your plaster

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┬áthat 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 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.

8 thoughts on “6 Reasons to Keep Your Plaster”

  1. Hi Scott,

    I have an old 1920s bathroom that is 100% mortar walls. I recently decided to put a niche in the shower wall. I removed the old tile, excavated out the old crumbly mortar and installed a box. I then repaired the area with hot mud plaster (Plaster of Paris) and coated that with 2 coats of Redgard. Then over that, modified thinset and tile. Did I screw up? Do you think I should have gone with a portland cement product instead of the plaster? Thanks.

  2. We wound up removing two interior plaster walls in one room and the ceiling. It was beyond repair and it makes me sad. I have tried calling several of the places in the area and they keep telling us they only work on old commercial buildings not residential. Makes me sad. My husband and I are trying hard to learn the trades but this is one we are scared of doing. Thanks for the fantastic blog.

  3. And then there is the aesthetic of the slightly imperfect. Not only that is seen, but there is a cumulative viceral effect of all these retained surfaces… I find the difficult part is to know when to stop the resoration, and let the imperfections show. Wabi sabi sensibilities.

  4. Scott
    Thanks so much for info on STC and Insulation rating, all great selling points for an OLD house. We have a 1910 Craftsman and I wish I could find someone to install lath and plaster where the previous owners took out walls. I think this is a lost craft and one that will not be back. Such a shame.

      1. Amen to that I just moved to the Pacific NW and LOVE the old old homes I get to work on. I helped a local restoration carpenter in New England growing up as one of my first jobs and love the old Craftsman homes. Was relocated to Coastal NC for a long time and just missed those late 1800s early 1900s home. Grew up in an old Lathe and Plaster farm house in the Connecticut Valley and have such an appreciation for the tried and true generstion after generation homes and I stumbled across your blog and am so thankful I found it. Awesome information.

  5. And firefighters love plaster walls. Our fire marshal told me that except to save a life, his firefighters do not go into newer houses, but old ones – yes.

Leave a comment!

Keep the conversation going! Your email address will not be published.

*