Walkabout: Plastered, Part Four

plaster repair 2 1

When you stop and think about it, a wall (or a ceiling) is a canvas. It’s a large flat surface that we hang wallpaper on, or paint. Just because we are painting our entire canvas in one color doesn’t mean we aren’t creating a painting, just the same. So if our canvas has lumps and craters and missing pieces, why not use real canvas, or in this case muslin, to cover it up, and in the process create a nice flat smooth surface for our artistry? It sounds so simple it’s almost embarrassing. Well, that’s just another of the plaster repairs that have been developed over the years. We’ve gotten all technological and space-agey with our building materials. So much so that sometimes we forget that the simplest methods are often the best. And those methods can perhaps be tweaked to be even better than they were originally.

We’ve been talking about plaster walls and ceilings. We’ve gone from a history of plaster walls in Part One, to a history of drywall in Part Two, to the traditional methods of plaster repair in Part Three. Today, we’ll finish up plaster repair and talk about drywall repair and the use of drywall in conjunction with traditional plaster. For many of us, the two different substances have worked together in many of our older homes, a compromise we’ve made, primarily because of budget, but also because of ease of work, time, and availabilities of materials.

A traditional repair to a plaster wall involves creating a new patch that is made in the same method as the original wall. That involves the use of the original wooden lath, perhaps augmented with a metal screen lath, and perhaps some reinforcement, such as plaster washers and/or fiberglass mesh tape, or paper plaster tape. The layers include a scratch coat, middle coat and final skim coat of plaster. A good plasterer can very easily wield his tools and a plaster medium to create a patch that is as smooth and indistinguishable as the original walls around it.

But what if you want to reinforce an entire wall, or ceiling, and add a new skim coat to the entire surface, not just a patch? One of the tried and true repairs of old is making a comeback – muslin, and its more modern equivalent, fiberglass mesh. Muslin is a plain woven cotton fabric that has been used for centuries for everything from clothing to storage bags to shrouds. Depending on the quality and fineness of the threads, it can be quite thin and delicate, or tough and utilitarian. For most purposes, it’s a natural yellowish ivory color, but can also be bleached white.

Way back when, someone figured out that a thin layer of muslin made the perfect backing for plaster walls that were going to be wallpapered. The muslin smoothed out any flaws in the plastering, and formed a good absorbent surface for wallpaper paste. A much better surface than plaster, depending on the circumstances. A muslin underlay is still often found underneath old wall paper. The layer of muslin is very thin, and after a century, usually can be removed pretty easily.

Many plasterers and restoration experts still use muslin today. It serves the same purpose as a century ago, creating a smooth layer that covers minor cracks in the plaster, and protects the wall. It is adhered to the wall with glue. The muslin, cut into manageable strips, is soaked in a solution of white glue, like Elmer’s, which has been quite diluted with water, then hung like wallpaper. The strips are slightly overlapped at the seams. The muslin is smoothed flat with a wide putty knife or squeegee, removing all creases and bumps. After the surface is smooth and allowed to dry overnight, wallpaper can be hung, or a new skim coating layer could be troweled on.

A modern variation of this technique very much in favor today is the use of a thin fiberglass mesh, instead of muslin. Many renovators who want to keep their plaster walls, but need to cover up cracks, large holes from electrical or other work, or any kind of holes or damage, are going with this method. Many homeowners are also concerned with toxic substances like lead paint or asbestos, and are using this method to encapsulate the walls to prevent any contamination.

After repairs to the plaster are done, a glue-like substance is rolled onto the walls. Common brand names are Plaster Weld, Wellbond, and Well-Crete. Some of it smells just like Elmer’s glue, and many plasterers still use an Elmer’s solution, and say it’s the same stuff, new marketing, and more money. While the glue is still tacky, the fiberglass mesh is applied to the wall. It’s similar to fiberglass plaster tape, and comes in rolls that are 36” wide.

The entire wall surfaces are covered in fiberglass, and like with muslin, after the walls are completely dry, a new skimcoat layer of plaster can be troweled on and smoothed. The new plaster coating keys into the fiberglass and glue, and forms a solid bond. The result is a new and beautiful plaster wall that is tough as nails, and smooth and silky as the day the walls were originally finished. Paint, wallpaper, or another decorative treatment follows. This method has become the preferred plaster renewal treatment in older plaster walled homes today. It’s not cheap, but could be done by a handy homeowner. The hardest part is the skim coating.

For those who want to repair plaster walls with drywall patches, instead of plaster patches, it’s simply a matter of using the right thickness of drywall for the repair. The hole is still prepared, as discussed in our previous chapter, with plaster repair washers on screws to fasten the good plaster to the lath. A length of drywall is cut to fit as well as possible into the hole. You may have to enlarge the hole to create a workable rectangle or square.

The patch is screwed to the lath with the same plaster washers and screws. Those same screws can also attach a piece of fiberglass mesh to the wall, or you can use pieces of fiberglass tape, which has a sticky surface. The new skim coat goes on over the entire surface, and the edges are feathered out to blend with the surrounding plaster, or sanded down. Voila, new wall. It’s a relatively simple DIY project, if you are handy, and a less expensive job than a traditional 3 layer plaster patch. It all depends on your wallet and/or your sense of purity in terms of authenticity towards original methods.

If you have drywall wall and ceiling surfaces and need to do repairs, it can be easier to do them with drywall, as compared to plaster, but drywall has its own quirks that can also make it difficult, too. If you watch home repair shows, which I do quite often, you always see the homeowners or the renovators doing demo on their drywall covered walls. It usually doesn’t take much effort for a sledge hammer or a booted foot to go right through a wall. That is followed by wholesale wreckage, as you can take a work gloved hand and a hammer and tear down a wall in no time. Interior walls generally have nothing in them but studs, perhaps some electrical wiring, and two surface walls of drywall. It’s amazingly flimsy.

Many times, interior walls are not insulated, so they are basically just hollow. This is why many people loathe drywall and new construction. These walls are not soundproof, quite the opposite, in fact, and they don’t hold up well over time. A kid with a Tonka truck can put a hole in your wall, so can a doorknob being slammed into it over and over, so can hanging pictures or shelves, or shoving a table too hard into the wall. Drywall is much more fragile than plaster, and it’s only the thickness of the paper covering that’s holding it all together. But if that’s what you’ve got, and it needs repairing, here’s how to do it:

Small dings, screw holes, etc. can be filled in with drywall compound, and smoothed with a putty knife. Simply load the surface of the knife with a small amount of compound, and at an angle, pass it over the hole. You probably will have to pass it over a couple of times to get the compound in the hole, and to feather out the edges so they are smooth and blend in with the rest of the wall. Some people can do this easily; others can call someone in to do it even easier.

Larger holes can be easy repairs, or can get tricky. It all depends on where they are in the stud wall. A hole is generally expanded by taking a drywall knife and cutting a larger square or rectangle, larger than the hole. If you find you are right on a stud, you’re in luck. But chances are you won’t be. Your drywall patch needs something to grab onto, a stud that you can screw the patch to, ideally. If there isn’t one, you have two choices.

You can create a surface by gluing or screwing a piece of wood or metal lath into the wall which would become a stud wall for the repair. You would then place your drywall patch in the hole, and screw the patch to the new stud. The idea is to have a supporting surface for your patch. You don’t want it to collapse back into the wall at the first sign of stress.

Or you can buy a pre-made drywall patch. It’s basically a wire mesh backer with an adhesive on the flanges that adheres to the back side of the drywall surrounding the hole. The mesh surface creates a stud wall, and the adhesive keeps it in place. You then can screw your drywall patch to this. The patches are for relatively small holes, the idea being that if your repair is huge, you probably will be exposing stud walls anyway, as by code they are 16” apart.

Whichever method you use, the steps are the same after the patch is attached to the wall. The rough edges are patched with compound, fiberglass or drywall tape is put over the edges, and the whole thing is covered with a skim coat. The skim coat is allowed to completely dry. A damp sponge is always handy to smooth out the surface. Edges are feathered out, and if done right no sanding is needed. If it’s a bit rough, sand as needed, and paint. Make sure you are using the same paint as before, and the same kind of paint. A glossy repair on a flat painted surface shows up more than the original hole in the plaster.

So, this has been a VERY rudimentary set of essays on plaster and drywall repair. For do-it-yourselfers, today’s media technology has made it so easy to find help. You Tube is loaded with video tutorials and step by step instructions on how to do all of the techniques I’ve mentioned and many more. More and more time saving products have been developed. In the course of the forty year resurgence of interest in old houses and their restoration and care, all kinds of traditional products, as well as brand new products to help preserve our plaster and other original details have been made available.

Drywall has come a long way, and today’s educated homeowners know much more about what they want and need from this time saving material. Doubling drywall layers may be what a homeowner needs to come closer to the plaster walls of old. Or a thicker skim coat may do the job. It all depends on your budget and your needs, and the compromises we all have to make to get what we want. The key to all of this is education. Even if your involvement in repairing or replacing your walls and ceilings is confined to writing the check, it behooves you to know what is going on. Those tutorials on You Tube, as well as a DIY magazine or two would be good to watch and read, so you have a clue and don’t get ripped off.

Speaking of ripping off, I’m in the process of stripping the wallpaper in what was the original dining room. There has always been wallpaper in this room, and under the 1950s rec room paneling, and under the three layers of wallpaper is the original plaster. Except for one wall, which had water damage from an upstairs leak, it’s in fine shape. I’m enjoying just looking at it, for now, as I figure out what I’m going to do. It’s over 110 years old, and still as solid and smooth as it ever was, except for some very minor dings and nailholes. That’s my cover picture up top. Thank you, long gone anonymous craftsman. I’ll try to take care of it so that it lasts another hundred years.

Tools of the trade. Photo: drywall- maintain.com

Tools of the trade. Photo: drywall- maintain.com

Fiberglass mesh. Photo: cornishlime.com.uk

Fiberglass mesh. Photo: cornishlime.com.uk

Fiberglass mesh repair. Photo:norfoss.com

Fiberglass mesh repair. Photo:norfoss.com

Drywall repair. Photo: diynetwork.com

Drywall repair. Photo: diynetwork.com

Photo: repairbuzzle.com

Photo: repairbuzzle.com

4 Comment

  • We have skim coated both with and without the fiberglass mesh. After about six months, fine hairline cracks and alligatoring appeared all over the newly skimcoated walls that did not have the fiberglass mesh. So the mesh is essential. Also, when we hired plaster experts who do only plaster, not drywall, including decorative plaster, we were interested to observe that they also used Plaster Weld and mesh. If your original plaster walls are in good shape, though, as in the above photo, I don’t think there’s any reason to add it. Just prime and paint.

  • I’m afraid I’d end up as a muslin-wrapped mummy if I tried to cover a wall but love knowing how it should be done.

  • It would be so helpful if we could print this whole series on plaster — pictures and all. It’s such a valuable resource! Any chance of that?

  • I reapeat what I posted under the first of this series….This Old House is currently doing an Italianate house in MA and just uncovered a beautiful plaster ceiling with crown moldings and medallions. Some reapairs are necessaryt and they will be addressing them in an upcoming show. I’m sure it’s also available online to watch after it appears.