Disturbing lead-based paint by sanding, scraping or demolishing its surface is considered the most dangerous way of dealing with it. If you have an old plaster wall that is covered in lead paint, tearing it down and throwing it in a dumpster creates a huge amount of dust that may be toxic. This is one more reason we recommend using Big Wally’s Plaster Magic to reattach plaster to lath. With reattachment, little dust is produced, and paint disturbance is kept to an absolute minimum (below the six square feet EPA threshold per room). Think about the dust produced by a complete tear-out versus a few dozen small holes drilled in the wall with plaster reattachment (watch our instructional video to see how reattachment works).

Lead is most dangerous to young children and pregnant women. Developing bodies are more apt to absorb dangerous amounts of lead. Because babies routinely put their hands in their mouths, they are at high-risk of lead poisoning after touching contaminated dust in or around a home. Adults face dangers as well. Reproductive problems, high blood pressure, nerve disorders and concentration problems have all been linked to lead poisoning.

Most American homes containing traditional plaster were built before World War II, meaning they are candidates for lead-based paint. Big Wally’s Plaster Magic is proud to offer a safer, easier alternative to plaster wall and ceiling tear-outs while preserving the beauty of historic plaster at the same time. We strongly recommend that you contact a certified and/or licensed contractor before you begin any renovation project where lead paint may exist. The EPA’s official website is a great source for educating yourself about the hazards of lead paint, testing methods, precautions and solutions.

Good luck, be safe, and happy plaster repairing!

Thus, we present to you a plaster repair glossary. Read them, study them, memorize them and wow all your friends at cocktail parties when you explain that a “hawk” is not only a bird of prey of the Falconiformes order, but also a flat sheet of metal with a handle, made to hold globs of wet plaster during the application process.

Plaster Repair Glossary

Aggregate: Mineral based, originally sand, serves as a shrinkage compensator, stabilizer, and bulking agent for plaster.

Building Efficiencies: Historically structures were built with materials that could be obtained locally usually for economies sake. People used what they had close by.

Carrying Capacity is the amount of lime (or gypsum) that any sand has the ability to carry for the perfect plaster (mortar) formulation for particular sand. This is determined by a volumetric test.

Crazing: Tiny cracks or fissures usually caused by rapid dry out while curing.

Delamination: The separation of plaster layers, where one layer separates from another or plaster from its lath.

Efflorescence is a surface deposit of salts (it looks like mold on the surface of the plaster) carried by moisture. The salts either come from the sand or gypsum in interior plasters.

Emley rating is a measurement of plasticity; a rating of 400 is considered good

First Coat, Scratch Coat: The first layer of plaster applied, its function is to hang onto the lath and when scratched provide a mechanical bond for the brown coat to hang on.

Fiber binder used in lime plaster, must not be alkaline resistant

• Hair: in this country cattle hair was used mostly, followed by goat hair in frequency. Lime plaster was “haired up” just prior to application as the lime would dissolve the hair when wet

• Hemp was the strongest fiber used in lime plaster; it gets stronger in an aqueous lime environment

Gypsum CaSO4•2H2O sedimentary rock processed by crushing and heated (calcined) to boil off the water within the crystal structure

In-Kind s the ideal composition for replacement plaster, this ideal trumps ASTM and Master Specs for matching historic plaster. It is more important to be similar than textbook “correct” or “ideal” as historic buildings were not built according to ASTM.

Lath is the material that the plaster is applied to.

• Wood laths are sawn roughly 1 1/2″ wide by 1/4” thick and 3-4 feet long made form whatever wood was available locally. In early New England accordion lath was used — 3/8” boards were applied to the framing, split with a hand axe and stretched, opening up keyways in the board to hang the plaster on. This is also known as “building efficiencies” (There was limited man power and abundant mechanical water power. Down south riven lath was used into the mid 19th century, where there was abundant manpower and limited water (mechanical) power)

• Metal lath, pierced metal lath was used from the turn of the 19th century to the 1940s, depending on where in the country the building was located. Welded wire lath was patented in England in the 1790’s; today it is known as hardware cloth. Diamond lath is another name for expanded metal lath and is the most widely used modern lath.

Lime either CaOH, CaCO3, or CaO

• High calcium is when the lime is up to72%- 98% calcium carbonate

• Dolomitic is a lime that can have about 35-40% magnesium carbonates

• Lime stone CaCO3 native sedimentary form of lime found in quarries; metamorphic form marble.

• Quicklime CaO, the initial product from the burning of limestone; a process which drives off the water, carbon dioxide, and carbolic acid.

• Lime putty CaOH is calcium oxide that has had its need for water satisfied and is turned into a paste which is the basic building block for traditional plastering.

• Lime cycle: The limestone is burned into calcium oxide, slaked to lime putty or calcium hydroxide, mixed into plaster and carbonates into a limestone-like material.

Map Cracking: Wide cracking that looks like a road map; often seen in turn of the
century lime plaster over terra cotta as well as developing over time in historic plaster ceilings

Plaster is a paste-like mixture of lime and/or gypsum, sand, and water, sometimes with fiber (hair or plant) added, that hardens to a smooth solid
wall/ceiling coating.

• Mud plaster, mixture of earth and water, often containing some but not necessarily all of the following: spanish moss, animal hair, sand, clay, and plant fibers, peat, straw

• Lime plaster a plaster mixture containing chemically active lime, hair or plant fiber, and sand…a thin bodied plaster must be applied in layers no more than 5/16” thick to allow for crystallization by interaction with atmospheric carbon dioxide, the lime must have a large surface area that allows capillary action to develop the slow evaporation of water at the same time as the air is allowed to come in for crystallization

• Gypsum plaster, a plaster mixture containing chemically active gypsum, and aggregate, sand or perlite, a thick bodied plaster sets by the addition of water into its crystalline structure; it must have enough water and body to supply to moisture for crystallization, suction from the substrata, and evaporation

Plasticity is plaster flow characteristics or how easily the plaster flows from the trowel and stays where it is placed. On a micro level the water acts a lubricant between the particles of mineral allowing them to flow under high shear and to stay in place under low shear, taking advantage of water’s surface tension and cement interaction.

Reattachment Adhesive is specifically designed to and used to secure and stabilize historic plaster to its lath, either wood, brick, terra cotta, or masonry; one manufacturer is Big Wally’s Adhesives, Inc.

Second Coat, Float Coat, Brown Coat applied to the scratch coat this layer is flat and level, floated to a light texture for the finish layer to be applied to… its purpose is to fill in the scratch coat level, plumb and square.

Secure and Stabilize is the basis for plaster repair. Once the plaster is stable everything else is cosmetic. This is accomplished by reattaching the plaster to the lath, using the lath to bridge cracks, reinforcing the whole plaster/lath structure.

Suction is the amount of moisture the substrata pulls from the plaster; this can be the lath, the air or another layer of plaster.

Stress Cracks are caused from building movement overcoming the ability of the plaster to stay intact.

Volumetric Test: Determines the carrying capacity of the aggregate (sand) allowing for an ideal (proper) plaster composition by measuring the volume of air space in any given aggregate. This air space represents the correct amount of cementious material in ratio to a specific aggregate.

White Coat, Finish Layer, Setting Coat, Putty Coat this is a thin layer used to fill in the cosmetic defects of the brown coat resulting in a smooth white finish that is occasionally left unpainted. Its purpose is mostly cosmetic while providing an abrasion-resistant surface.

The ad was for a carpet cleaning service. Two cleaning techs are driving down the road in a company van when they see a worn-looking rug rolled up and tossed out on the side of the road for trash pickup. The driver of the van slams on the brakes, dashes out of the van and kneels beside the rug. “No!” he cries. “I could have saved this one.” He glances up at the offending house… “I could have saved this one!”

We know EXACTLY how that carpet tech feels. The same sense of sadness and confusion wells up in us every time we drive by a dumpster filled with broken lath and crumbled-up plaster. “WHYYYYY!?”

It kills us to see it, every time. That plaster — that beautiful, irreplaceable, historic plaster — could have been saved with a little know-how and the right repair materials. In most cases, we have to assume that it’s not that homeowner or renovator’s fault – they simply don’t realize that there are products like Big Wally’s that can spare old walls from spending an eternity in a landfill. By using an adhesive to glue plaster back onto its skeletal lath, that vintage wall can be saved.

“But,” you might be thinking, “it’s probably cheaper to just rip that old wall out and put up new material like drywall or brand new plaster.”

As my carpet cleaning friend would agree, it is not cheaper. Or faster. Not only that, but your home or historic structure will almost certainly lose value if you replace tried-and-true plaster with inferior modern materials. Big Wally’s Plaster Magic saves this long-lasting, consistently underrated interior finish. Interiors which plasterers (not repairers) have given up for lost can be fixed quickly and easily. Using this method saves walls or ceilings which would otherwise be lost.

So please, everyone, think twice before you decide to scrap that beautiful plaster wall or ceiling. We can save that one. We can save that oneeee!

At this point, you may be expecting some tips on maintaining your plaster walls and ceilings. But it’s not the plaster that needs maintaining, it’s the structure supporting it.

Let’s look at a typical problem in New England houses: ice dams. Ice dams occur when heat escapes from an incorrectly insulated house and melts snow at the eaves of the roof. The water then runs to the edge of the roof and freezes solid. The resulting dam pools enough water behind it to seep back beneath the shingles and leak into the house.

Though you may not see it, that water can trickle down into the walls and saturate your historic plaster, resulting in costly repairs. That water can also warp or rot the studs and wood lath, compromising the plaster’s “skeleton” and ultimately causing the plaster to crack.

Now let’s look at a common problem that exists throughout most of this country (you’re off the hook in the southwest desert)… moist basements. Without proper airflow and dehumidifying, moisture beneath your ground floor can lead to rotting joists and sill plates. This leads to sagging floors, which leads to shifting walls, which leads to, you guessed it, cracked plaster.

We’re proud of you for doing research on plaster repair and considering Big Wally’s Plaster Magic to get the job done right. But before attempting any plaster repair project, ask yourself, “why did it fail in the first place? What is at the root of this problem?” It could be a shifting foundation due to poor drainage around the periphery of the house; clogged gutters and downspouts are often the culprit in this situation. It could be due to a broken seal around a toilet that’s been slowly leaking without you knowing it. It could be sagging joists or rafters due to the location of uneven weight loads throughout your house (such as rooms stacked with boxes of books). It could be that the flashing around the base of the chimney needs to be sealed again. What’s the point of spending the time, effort and money to restore your beautiful plaster if the problem crops up again in a year or two?

Good luck with your repair and as always, drop us a line at info@plastermagic.com or leave a comment below if you have any questions.

Janine writes:
“I’m looking at contractors to deal with the big holes but have started using Big Wally’s for D.I.Y. crack repairs (about 250 linear feet). I’m on my 5th tube or so of adhesive and I’m getting less sloppy with dripping conditioner and backflow of adhesive. Still, when I spray the conditioner in, lots drips back out. Any tips (other than practice) for ceiling work?”

First off, kudos for having the courage to tackle this ceiling plaster repair job yourself, Janine. We love to see homeowners doing repairs the right way and making the effort to preserve historic plaster.

Thanks to gravity, ceilings present a unique problem when it comes to conditioning the lath and plaster in preparation for the adhesive. Indeed, the liquid will want to drip back out. I have discovered one tool that helps, though — a pressurized garden sprayer, which you can pump as much or as little as necessary to produce a stronger stream than the standard spray bottle. You can purchase these sprayers at any home improvement center. The stronger stream will penetrate deeper into the lath-work, resulting in less back-drip. Additionally, I’ve found that simple clay plugs inserted into the holes keep the conditioner in (just make sure you remove the plugs before injecting the adhesive behind the plaster).

Also, make sure you go around the perimeter of each hole and glue the plaster at every lath. This will stabilize the open edge of the old plaster, keeping it secure.

Thanks, for your note, Janine. Good luck with the project and let us know how it turns out. And hey, send us some photos of your progress to info@plastermagic.com so we can share your work with the world.

Of course, you can’t just grab a wheelbarrow full of gravel from your driveway, grind it to dust, add water and spread it on your wall. There’s more to the recipe.

What’s in plaster anyway?

Clay, lime, gypsum, sand, animal hair, cement and mud have all made their way into various mixes. Plaster has been around for thousands of years, and in the days before motorized transportation, builders simply used the materials available close by. Crafty builders in Louisiana, for example, have been known to mix swamp mud, Spanish moss and deer hair to make a plaster material they call “bousillage.”

There are dozens and dozens of different ways to mix plaster, but for now let’s talk about interior walls and ceilings in American homes. In American architecture, lime was once the most common material used in interior mixes. When mixed with water, sand and horsehair, the peanut-buttery substance was applied and allowed to set. Once dry, you were left with a hard (yet still somewhat pliable), durable surface that closely resembled a slab of limestone.

Around the early 1900s, however, gypsum became the “rock” of choice in American plastering. Made up of calcium sulfate dihydrate, gypsum is still the standard we see in most interior mixes today (it is also the main ingredient in drywall). It is the main ingredient in Plaster of Paris, too.

What holds plaster together?

Still, something is needed to bind all those ingredients together once they dry. In the same way that thin rods of re-bar are encased in concrete to give it enhanced structural integrity, lime-based mixes use some sort of fiber binder. In antique America homes, cattle or ox hair was a common binder.

Modern mixes, however, doesn’t need fibrous binders. Instead, it utilizes the crystalline particles inherent in the gypsum. When those crystals are allowed to become wet, they lock into each other during the drying process.

Have more questions about the makeup of plaster? Leave us a message in the comments below.

To date, the earliest evidence of plaster was found in portions of southern Turkey and northern Syria. Plaster was applied to the houses there around 12,000 B.C. That’s before pottery was even invented.

In its most pure form, plastering has not changed much in 14,000 years. Wet “mud” is still spread over some type porous surface until it is smooth. It is functional, durable and looks great – that hasn’t changed. The tools and ingredients have undergone some evolution, though.

In the beginning, simple wooden tools and clay/dirt mud were used. During ancient Egypt’s height of power, gypsum was incorporated. The Greeks had lime and the Egyptians had gypsum… they both used the local materials that were were available.  The Romans, in turn, took cues from the Greeks, spreading the power of plaster through the Roman Empire.

Nowadays we have access to modern, heat-treated stainless steel and plastic trowels. The Industrial Revolution of the late 1800s brought big changes in binders used in plaster – oil provided controllable energy and the heat necessary to process these binders, and more importantly to provide transportation for plaster to be distributed over a wide geographic area, negating reliance on local materials.

Due to English influence on our culture, the first plaster used in the U.S was a clay-lime-hair-sand mixture called daub, which was applied to wattle, thus the name “wattle and daub”. Gypsum and Portland mortars and plaster were phased in during the early 20th century, as they allowed building production schedules to move forward faster.

Today we enjoy a wide selection of  plaster types, each tailored for a specific purpose or climate, be it plaster repair in Milwaukee or new veneer in Miami. Whether it is gypsum formal work, veneer plaster, Venetian plaster, traditional lime-sand-fiber plaster, or ultra-modern synthetic plaster, builders have a myriad of options. Every one of these materials has its inherent strengths and weaknesses. Knowing the properties of each material allows a builder to determine the correct plaster to use in any given circumstance.

The number one at-risk historic material in this country is interior plaster. Historic plasters can be fixed and preserved to be part of a cost-effective restoration process. Modern alternatives do not measure up in the long run to maintaining historic plasters. Sadly, in the 20th century, maintenance was often considered an unfortunate side effect of house custodianship. In this new century people are now reaching back to preserve our collective architectural history.

Read the full article here at This Old House online

Rory Brennan demonstrates a different plaster repair method from Tom Silva’s, one that reunites the sagging and cracked 135-year-old plaster with its lath-strip supports. By affixing this loose ceiling with an acrylic adhesive that he injects through 3/16-inch holes throughout the damaged area, Brennan can make repairs without adding permanent hardware to the plaster surface. He draws the plaster back to the lath using screws fitted with protective plastic washers. Once the plaster glue has set, he removes the screws and washers, and fills all the holes with a rapid-setting plaster mixture, smoothing away all the blemishes.

When time and money considerations are combined to analyze a plaster problem a repair is the soundest investment one can make in a building. Lime sets over extended periods of time; it’s young at 100 years. This slow cure helps to impart the qualities that make plaster a viable candidate for maintenance and repair. Properly cared for lime plaster will last forever – there is no other plaster that can make that claim. The existing plaster must be reattached to the lath, making it stable and secure in its original position prior to patching. Without being stabilized, nothing else done to repair the plaster will last. Once stabilized, almost any repair will last.