Cementitious Man                                      For all your cementitious needs
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Plaster Info
A Little Background on Your Walls and Ceilings

If your home was built before 1950 you most likely have traditional lath and plaster walls. Wooden lath strips are nailed across the framing and then plaster is applied to the lath strips, The plaster that oozes between the lath strips is called the key. The key locks the plaster and lath strips together.

        If your home was built around 1950 you could have one of several versions of lath-rock and plaster (the precursor to drywall). This was a plaster board of varying sizes that was nailed onto the framing and coated with a traditional three coat plaster in the beginning years. You'll know if you have this because your walls will be an inch thick or more. In later years they switched to a much thinner veneer coat over the plaster board.

        If your home was built before the 1940's then you will also have calcimine. Calcimine = chalk paint, an easy way to think of it.  Calcimine eliminated the 60 day cure time for fresh plaster mixes of that time. The chalk allowed the lime in the plaster to off gas with no ill effects whereas oil paint will blister and peel off as the lime gasses escape if painted before 60 days.  Why do you care - if the calcimine gets wet from a roofing or plumbing problem then the paint or wallpaper trying to hold on to the calcimine just lets go.  It's most likely what you've been staring at that eventually lead you here. If you have a weird bubbly spot usually accompanied with brown staining (tannin leached from the wet wood)  then you have had water intrusion. Calcimine gets wet, things  let go. This is also the cause of cracks turning into mountain ridges. Plaster is hygroscopic, it seeks out moisture. A crack develops from settling then the plaster draws in any ambient moisture, the calcimine gets wet and the edges of the paint/wallpaper begin to slowly curl away from the crack, thus ridge. If you'd like to read more about calcimine, go here http://www.plasterlord.com/notebook/fcalcimine.htm 

       If you didn't cover every surface in your home with wallpaper at the beginning of the last century then you just weren't hip. So you are possibly looking at layers of wallpaper over your calcimine coated plaster. If you're lucky someone else has already removed the wallpaper  or you have wallpaper that is firmly affixed to the wall or ceiling. If not, it may be time to remove it. 



Do you have to repair cracks in plaster?
No you do not.  Give them names, watch them grow and be proud. It's all cosmetic, they either                bug you or they don't.

How do I tell if the key is broken or missing?
If you see a bulge or bump you can assume the key is gone. All of your wall or ceiling should lie in
         the same plane. An easy test is to put a 3' straight edge over the crest of the hump and rock it back          and forth.  If your straight edge is an inch off the surrounding surface you're most likely missing              the key.

Do you have to repair unkeyed plaster?
Sooner or later, yes you do. Plaster is very heavy. Once it is not keyed into the lath,  gravity will               begin pulling it down popping more and more keys until - boom - it hits the floor.

Should I rip out all my old plaster?
   The quality of old plaster walls and ceilings is largely dependent on the original plasterer. If you              have good plaster walls they will outlast drywall  and make your home much quieter. I have
           run into homes where the original plasterer was a cheapskate and saved money by skimping on             the plaster in the base coat. Leaving you with a very weak crumbly base coat and key. In this                     situation I would remove the plaster.  In over twenty years I've only run into this about three                  times.

Can you match the texture of the plaster?
Yes I can.

If I have water damage will there be mold?
No. Water does not really hurt plaster if it is allowed to dry out again. I routinely soak down                   walls in the course of my work. A continuous leak over years will cause the framing and lath to
            rot and the plaster falls apart. I only encounter mold when wallpaper is involved. Wet paper and
            wheat paste is a breeding ground for mold.

Do you repair drywall?
Yes I do. I will also install a plaster veneer over new drywall that you have hung. I do not hang                  drywall.

How do you keep the cracks from coming back?

I cover 100% of the wall or ceiling with Yellow-Jacket Fiberglass mesh embedded in the
  This gives you an anti-fracture membrane covering the entire surface and preventing
              cracks in the future.  I've never had a call back about cracking with this system in 20 years.                        This will not stop the processes of nature, if your house settles dramatically it will stretch
              beyond the endurance of the fiberglass, but it should be a very long time before that happens.

Do you create a lot of dust?
No, no sanding, no drywall dust. The messiest part is removal of faulted plaster and paint.
              During this stage plastic walls are used to contain any mess.

Do you do small jobs?
  I do but I have a $500 minimum charge so you may want to look for a couple other spots                           to repair.

Are there any circus aspects to your work?
Why yes, I often work on stilts.      
Do you listen to strange music at loud volumes?
Whenever possible.

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