First there was stone, then there was plaster. More than 3400 years ago plaster coated walls were common enough to be mentioned in Biblical writing. Leviticus 14:41 details the purification of an unclean house, including “And he shall have the inside of the house scraped all around, and the plaster that they scrape off they shall pour out in an unclean place outside the city”.
In other parts of the world, where stone and plaster weren’t as easy to come by, earthen work buildings developed. Wattle and Daub buildings were built using a basket work of supporting stakes and thin wands of willow or other flexible cross-pieces. The whole basketwork was then covered with a sticky mixture of mud, sand, straw and even animal manure. Evidence of wattle and daub construction dates back more than 6000 years and it is still used in some parts of the world.
The lathe and plaster construction used in houses up until the 1950’s is a logical evolution from wattle and daub. The studs of interior walls were covered with thin strips of wood (laths) and then coated with plaster. The plaster seeped between the gaps in the laths and formed a solid layer. After the first layer dried a finish layer covered the wall and it was ready to be painted.
Age and settling take their toll and, as in my house, the plaster can separate from the lath, forming cracks.
Just covering the crack with spackle or more plaster won’t fix the problem. The only way to repair the sag and stop the cracks in the plaster from spreading is to reattach the plaster to the lath.
Use a masonry bit to drill a series of holes on either side of each crack. Masonry bits don’t like wood, so when you hit a lath the drill will spin against a resistance but won’t drill any farther. If you hit a space between laths you will just punch through. Mark holes that miss a lath so that you don’t bother putting a screw into these holes.
Next, squirt construction adhesive into the holes. Use a caulk gun for this and only do a few holes at a time. Force enough glue into the holes to get it to bead up on the inner surface of the plaster.
Finally, drive drywall screws into each hole. I used 2-inch coarse screws. As you tighten the screws you will feel the plaster pull back to the lath. In researching how to repair drywall one suggestion I omitted was to put a washer under each screw. It seemed to me that the result would demand a lot more plastering to cover the repairs than just the screws by themselves. If I were to do this repair again, I would add the washers. They spread the force created by driving the screw over a wider area and prevent any additional cracking of the plaster. Without the washers I cracked the plaster in several places and ended up adding more work to my project.
The corner of one wall was cracked from top to bottom. In order to make this repair I used a metal corner bead.
I ran a line of adhesive along the corner and screwed the bead in place, pulling the plaster and lath together on either side of the corner.
After the repairs were in place I slathered the screws, cracks and corner bead with drywall compound, then covered them with mesh drywall tape.
There is also a paper drywall tape that you can use if you prefer. I like the mesh tape because you don’t trap air bubbles under the mesh and the final result is very smooth. Don’t try to rush taping. Let the compound dry between layers and sand any bumps and ridges smooth. Feather the compound away from the repairs so that the transition from the repair to the rest of the wall is smooth. It took me several days of layering and sanding to get the screws and corner bead completely concealed.
Be sure to prime the walls before painting. I know that most paints contain primer but I think the end results look better if you start with a sealed surface before painting.
Here is one little discovery I made while cleaning up the walls. Moly-bolts had been used to attach curtain rods to the walls. I wanted to start with a blank slate and when you pull moly-bolts out of the wall they leave a huge hole behind. I decided to cut them and push the part that didn’t cut back into the wall. I used my handy-dandy nail pullers and discovered that if I pried the flat part of the moly-bolt up a little bit and squeezed with the nail puller, the head of the bolt popped right off and the rest fell into the inside of the wall. I’m pretty sure they were designed to do this, but I didn’t know that so I am sharing it with the rest of cyberworld.
Finally! The walls are ready for the fun part of home remodeling! It’s time to paint!