When it comes to historic plaster repair and restoration, there’s definitely something to the old adage that “practice makes perfect!”
After all, this is why a professional plasterer has to apprentice for years before they’re formally allowed to work on anything that anyone is even allowed to see. Thankfully for us as DIYers, we don’t have any such rules, and we’re able to put our learning curve and imperfections on full display for all of you.
At this point we have over 15 years of amateur plastering experience in repairing anything from small sections of cracked or missing plaster, to complete room overhauls. My teenage self of the early ’90s just read that statement and cringed at what his life has become. Don’t worry 13 year old Alex, you’re even more lame at 13 than 40 year old you, you just don’t know it yet. Go ahead and play another game of Joe Montana Football on your Sega Genesis and call me when you’re less obsessed with Andre Agassi.
In our 15 years we’ve learned more about plaster than we ever expected when we first bought our historic home. Along the way we’ve picked up tips and tricks, we’ve made plenty of mistakes, and we finally feel like we’re starting to get the hang of this whole plastering thing…until we learn more that makes us second guess what we’ve done in the past and we begin to think we’re actually just total crap at plastering.
Oh, and we’ve even been featured in a published guide on how to attempt some DIY plaster repair (that makes some in the historic plaster repair community cringe because it used joint compound as an ingredient)! See ’90s Alex, all that time spent memorizing the lyrics to Rapper’s Delight and figuring out how to dance like MC Hammer have paid off, now you’re a pseudo plaster expert and can grow a semi respectable yet unreasonably creepy looking mustache. Dreams do come true.
All that being said, we’re feeling pretty good about the progress we’re making in our dining room, and we’d like to share the latest in our plastering endeavors with all of you. Our goal is simple, share our journey for entertainment and the hope our experience can help when it comes to work on your own home. At the very least you can see what we can do, realize that if we can do it, you can certainly do it yourself, and award yourself another virtual merit badge skill learned by reading a guide on the Internets.
Our dining room project is now the second room in our house where we’re going the more tried, true, and “appropriate” route of plaster repair. We’re using more traditional methods and materials to skim our patched and repaired walls, rather than the use of the more readily available and commonly leveraged joint compound.
You see, after years of use I learned that joint compound was once my crutch. I spent so much time slathering the cake icing consistency gypsum based paste all over our walls that I was blinded to the fact I had been mislead early on by the likes of an perpetually inebriated fellow DIYer and former neighbor that enjoyed telling tales of lime additives in the “green label joint compound,” home improvement television shows touting the advantages of skimming, and Internet message boards that informed me, “when one would like to get to fixin’ up their broken plaster, they should grab a bucket of mud, slap it on the wall, and get to sanding once it reaches a full cure.”
Not only did I learn this flawed technique, for years I peddled it as the righteous path forward as I shared our progress. But when it comes down to it, even though our walls and ceilings look rather lovely, smooth, and like beautiful old plaster some 15 years removed from the original work, there are problems. Primarily, they were a real mess to create, and they tend to ding and chip far easier than we’d like. This doesn’t mean we were wrong in what we did, simply that there’s a better way for future work.
When it comes down to it, we must challenge ourselves to grow and learn, evolving in our approach to plastering, much like our distant ancestors discovering that a sugary drink and a little added yeast allowed to sit for long enough in the right conditions turned them into delicious alcoholic beverages, which after sufficient chilling, can be used to celebrate the completion of a plastering job well done.
In our dining room plaster repair project we’re applying the skim in multiple coats and eliminating sanding as a part of our process (which is seriously cutting down on the mess and, as a result, improving spousal approval of the technique). And most importantly, we’re making updates that will hopefully stand the test of time and will preserve our home for many generations of future owners.
The missing plaster was patched in with drywall against the wood lath.
In our last post on our work in this room, we described how we had painstakingly prepared our walls. They had been plaster buttoned, scraped of liquid nails, and patched with drywall where necessary, At that point we were ready to begin putting everything back together again and making our walls smooth and solid. But before we could launch into the actual plastering process, we had to make sure our plaster had something to really hold onto.
Bonding Agent (Plaster Weld)
Our walls in this room have a very old coat of paint on them. This paint last saw the light of day in about 1992, and even then it was looking rather defeated, much like 14 year old Alex of the same era when he realized he possessed far too much inherent fear and not nearly enough athletic ability to become the next Tony Hawk. The paint beneath the drywall is missing in large sections, but it was intact enough to act as a barrier that could prevent the new plaster skim coat from really adhering to the walls.
In addition to the paint possibly preventing a good bond, the patches in sections where we used drywall to repair large missing portions of plaster needed to be prepared in order to ensure a good and solid surface that would accept the plaster.
When it comes to getting painted or drywall surfaces reader for plaster, or more specifically, ready for the Structolite base coat we’re using, you need to apply a bonding agent. Polyvinyl acetate, or PVA glue mixed with water is traditionally used by plasterers in Europe, but in our case we picked up a few gallons of PlasterWeld.
PlasterWeld is the Pepto Bismol pink bonding agent that can be painted onto the surface to be plastered and provides a suitable surface to which plaster can adhere while also preventing significant suction. Amazon has it but it’s somewhat expensive, but we found it through Walmart.com for just $26 per gallon.
Preventing suction is import to the success of the plaster’s ability to cure, otherwise water will be drawn out of the new plaster too quickly, causing it to dry prematurely, crack, and fail. This is why you paint the bonding agent over the drywall paper, as it has the tendency to suck the moisture from the plaster.
We painted the PlasterWeld on all of the new drywall and the portions of the wall that seemed to be most throughly covered by old paint. Once the PlasterWeld is applied, you need to give it at least an hour to dry, but can apply the plaster anywhere from about one hour to seven days after application. If you let it sit for longer than seven to 10 days, you risk losing the qualities that make it bond to the plaster really well…so don’t put it on and wait a few months to plaster.
Once the pink bonding agent with the odd but not entirely unpleasant scent was sufficiently cured and awaiting its upcoming coat of plaster, it was time to mix up a little Structolite.
Base Coat Plaster (Structolite)
We’ve talked Structolite in the past, but we’re much more familiar with the product now and really enjoy using it. You can pick up Structolite in 50 pound bags from either Home Depot or Lowe’s (and I’m sure many other locations), but check online to see if your local store carries it as it seems to be pretty hit or miss. We’ve had to order it and have it shipped to the store each time we’ve bought it.
When it comes to mixing the plaster we find filling a 5 gallon bucket half full is roughly the right amount for us that allows us enough time to apply all of the plaster without losing the workability. If you take too long and it begins to cure in the bucket, you’re pretty much out of luck when it comes to getting it on the wall, and your bucket is also a lost cause.
When you mix the Structolite it’s best to pour some of your water into a 5 gallon bucket, then slowly add in the plaster and mix. This allows you to ensure complete mixing of the plaster and will let you achieve the consistency you’re looking for, which is pretty much that of a Frosty or soft serve ice cream. (Plastering sounds delicious.)
This time around we’ve finally started using a hawk and trowel (rather than taping knife and trowel) to apply our plaster. The hawk presented a little bit of a learning curve, but it certainly helped get the material on the wall faster, and reduced the need for repeated trips to the bucket to refill my trowel.
Now I’m not saying I didn’t drop a whole pant-load of plaster on the floor on several occasions as I learned how to properly use the hawk, but now that I have more confidence and a little more experience using a hawk, I am never going to look back when it comes to plastering.
Since the next step requires embedding 48″ sections of reinforcement fiberglass screen (aka window screen) in the plaster, we set up our laser level to denote where each 48″ line was from the prior piece of embedded mesh. This was a much more effective approach to setting a boundary so I’d know where to plaster up to without going significantly over.
Embedding Fiberglass Mesh
As we worked around the room spreading the Structolite over the original plaster and patched areas (and over the Plaster Weld) we also methodically embedded fiberglass window screen as an isolation membrane of sorts. We’ve been using this approach behind both plaster and joint compound for over 12 years, and it has worked very well for our purposes.
The idea is to prevent minor cracks from beneath from transferring through to the surface through a decoupling layer of sorts. The mesh we’re using is nothing more than standard window screen. We buy it in rolls of 100′ and the rolls are 48″ wide.
These rolls are usually about $55-$60 but don’t go for the “extra strength” variety as it’s both more expensive and less forgiving. While we’re plastering Wendy rolls out sections on the floor as we plan out the room and I work around the joint plastering.
Since the laser level gives us a good boundary line we don’t risk premature curing of the plaster that would prevent the screen from being embedded and end up in an extra lumpy finish.
Once all of the Structolite plaster was applied up to the line Wendy would pass me another length of screen and I’d hang it at the top while she eyeballed the base to be sure I had good coverage. It doesn’t have to be a two person job, but it does make it easier. However, sometimes it’s necessary for the second person to go to the store to buy more screen because you ran out. In such a case, you can handle it yourself. Just climb up on a ladder and smoosh it into the plaster.
Then it was simply a matter of embedding the screen securely in the fresh plaster, making sure to apply it evenly, without wrinkles or ridges, and with adequate coverage. This is easiest to accomplish when you use a trowel to evenly apply pressure, top down, middle out.
In the corners we wrap the first pieces of screen around the inside corner by about two to five inches and embed in the plaster. Once that first pieces of screen is in good shape, we continue applying the next section of plaster and overlap the pieces of screen just shy of the corner. The overlap is important to ensure good coverage and protection against future cracks in the corners.
When dealing with junction boxes we like to take any boxes out and apply the screen right over the openings. Once the plaster cures sufficiently we cut out the plaster over the hole, and after the next coat of plaster, put any junction boxes back in. Since we’re adding some thickness to the wall with the plaster this ensures the boxes are not recessed below the wall’s surface.
When all was said and done with this first coat of plaster we had ourselves a room that no longer had massive missing sections of plaster, significant damage, remnants of old liquid nails, or evidence of the years of neglect these walls have suffered. We also had the first of three coats of plaster complete on our road to a beautiful dining room.
But wait! We have one more step before we’re done with this first coat! This is a tip we picked up to ensure a slow cure that results in a nice and smooth base coat to build on. Structolite plaster should cure slowly as the water in the material evaporates. The bonding agent (Plaster Weld) ensures the base doesn’t suck the water out of the plaster, but I’ve noticed it has the tendency to dry somewhat quickly when humidity is low, as it is in the winter…or in Arizona.
About 30 minutes after I finish applying the plaster I like to go around the room with a spray bottle and my trowel, gently misting the wall and using the trowel to smooth any ridges or high spots. This does double duty of smoothing the surface that will support the next coat, and also slowing the cure by gently wetting the curing plaster. Then after allowing the plaster to cure for about 8 to 12 hours (like after a night’s sleep), come back through and gently mist the plaster again to dampen it during its final cure. Again, this just slows the cure, helping to prevent any chances of cracking from a cure that happens too fast.
While this phase of renovation feels like it takes forever, it’s exciting to see the walls come together, so to speak. Now that they’re free of holes and patches, we can get a much better sense of how the room will look when finished. Just two more coats of plaster, and then we’re moving right on to trim work and molding!