Siding, stucco, plaster and drywall don’t hold up our homes, but it’s easy to see why people think they do. They are the stuff we wrap our homes with—inside and out.
The History of Plaster
Giving rough construction materials a finished surface is a quest as old as architecture itself. It all started with the discovery of gypsum, a mineral with some very special properties. Gypsum is extremely lightweight, crystalline in structure, dissolves in water, and has the ability to expel its absorbed water when heated.
The ancient Egyptians learned that if they heated gypsum over open fires they could cook out its water, leaving behind a dry chalky substance that could be crushed into a powder. When that powder was mixed with water again it became a temporarily spreadable paste that would dry to a hard, smooth surface without shrinking. The world came to know that material as plaster, or by its Italian name, stucco.
From the Egyptians and Babylonians to the Greeks and Romans, we’ve been building with plaster for at least the last 7000 years. In Europe, from as early as the year 500, the largest and purist deposit of gypsum was quarried in France in what is now the Montmartre district of Paris. Its high quality gypsum was sold all over Europe as Plaster of Paris.
It was the Italians who boldly started using a special plaster recipe—mixed with cement—on the outside of buildings. The Italian word for plaster is stucco, which is how exterior plaster came to be known as stucco (although in Italy it’s all stucco - inside and out).
Plaster (and stucco) originally just covered over solid surfaces like stone, concrete, and brick, but when architecture began shifting to lightweight wood framed construction there were empty spaces in between the wood studs and no continuous solid surface as a base for the plaster. That’s when the process of “lath and plaster” was born. Lath was a term for thin, narrow strips of wood nailed across the studs faces with gaps left between. The first coast of plaster (the scratch coat) was spread across the lath and pushed into the gaps so it would ooze just a bit on the back side. This was called “keying” and it would lock the plaster onto the wall. After the scratch coat was dry, several additional coats were added until finished. The average finished thickness of a lath and plaster wall is between ¾” and 1”. The finished thickness of a stucco wall is also 1”.
To this day, both plaster and stucco are applied in similar ways. Building paper and wire have replaced the wood slats, but it is still called lath. And there are still multiple coats, beginning with the scratch coat, whose job is still to lock itself into the lath.
How did we get from Lath & Plaster to Drywall?
Everybody picks on the new guy. When stucco was first applied to the outside of buildings it was called “the poor man’s stone.” When drywall was first applied to the inside of homes it was called “the poor man’s lath & plaster.”
Drywall is a panel of gypsum covered by a thick paper on both sides.
It was first introduced as plaster board (sometimes called “button board” because it had holes throughout) in the late 1800’s to replace wood lath and save time. It saved a LOT of time, and of course, money. Plaster board could be hung in a day and only needed one or two thin coats of finished plaster to be done.
The next evolution, “Sheetrock” was trademarked in 1917 but didn’t gain widespread acceptance until after WWII. By the 1950’s drywall replaced plaster board as a ready-to-paint surface that needed no plaster layers at all except for covering seams and nail holes.
By the 1960’s drywall was the dominant building process in North America to save time and labor over traditional lath and plaster. Plaster application was usually a week-long plaster process:
Day 1-2 - Cut and nail Lath
Day 3 - Scratch coat
Day 4, 5, 6 - Three finish coats
Day 7 - Sand and smooth final coat
Today an entire house can be drywalled in one or two days by two experienced drywallers, and drywall is easy enough to be installed by many homeowners.
- The ongoing domination of the wall & ceiling market by drywall comes down to cost, ease of install and ultimately … seamless surfaces.
- Drywall is naturally fire retardant
- North America now produces about 42 billion square feet per year.
- The average American home contains 7 metric tons of gypsum.
- All drywall sheets are cut from an original single sheet that was 800’ long!
- Drywall comes in ¼”, ⅜”, ½”, ⅝”, ¾”, 1” thicknesses and lengths from 4’ to 16’
- Green board is moisture/mildew resistant drywall.
- Quiet Rock is sound dampening drywall - two layers of 1/4” drywall with a polymer filling to break energy transmission
- In 2010 came ultra-lightweight drywall - stronger, 25% lighter, more fire-resistant, and so sag resistant that ½” thick sheets can now be used on ceilings. A conventional 1/2-inch sheet of drywall measuring 4 feet by 8 feet weighs just over 51 pounds. At around 39 pounds, a sheet of 1/2-inch thick ultralight drywall weighs 12 pounds less than a standard 1/2-inch thick drywall sheet.
- Phase Change Drywall contains “micronal” beads of paraffin wax that melt at 72º thereby absorbing heat like an old style ice box! At temps below 72º at night they “freeze” again and are ready to absorb heat the next day. ⅝” thermal Phase Change drywall has the same thermal storage capacity of 3½” concrete or 4¾” brick
• One thing I want you to know about drywall … It’s not holding up your wall.
- Installing and finishing drywall is often split between hangers and tapers, or the float crew, who finish the joints and cover the fastener heads with drywall compound.
Drywall can be finished anywhere from a level 0 to a level 5, where 0 is not finished in any fashion and 5 is the most pristine.
- Level 0 - No finishing. Drywall is simply fastened to the walls or ceiling.
- Level 1 - Joint tape embedded in joint compound, but nothing else.
- Level 2 - Joint compound over the tape and covers drywall screw holes. Stop at this level if you intend to cover the wall surface with tile.
- Level 3 - 2nd coat of joint compound over tape and screws - plus knockdown
- Level 4 - Classic drywall finish. One more thin coat of joint compound to the tape and screws and sand the dried compound.
- Level 5 - Highest possible level - full skim coat
Best way to get a great drywall job … prep, shim and plane the walls beforehand
- Scored not cut
- Bugle head screws/nails compress the drywall without cutting into it. Goal hanging is to dimple board but not break the paper
- Specialized drywall screw guns, or buy a drywall dimpler bit
- Edges of drywall sheets are tapered for better tape coverage without bulging
- Taping Compound – Taping and second coat. Strong, very little shrinkage, resists cracking.
- Topping Compound – Final coat. Easy to use, dries quickly, sands smooth.
- All Purpose Compound – All phases—taping to the final. Most commonly used, but doesn’t have the same strength and stability as when using the taping and topping combo.
- Dry or Wet sanding?
- Fiberglass adhesive tape v. paper tape
- Corner bead
- J metal for uncovered edges
- Drywall T-square
- Hole saws
- Recessed can scoring tools and hole cutting bits
- Rotary cutout tools
- Edge Backing
- Cardboard Shims
- Drywall ceiling lifts and dust-free sanders at rental yard
The Future of Drywall
- J metal for de-emphasizing certain doors - including access hatch doors
- Drywall might just save the future …
Siding & Stucco Problems
Scratch to brown
International Building Code (IBC) Chapt 25 tables - 48 hours between scratch and brown.
However, section (2512.8 IBC) allows the “alternate double-back method”- brown coat can be applied as soon as the scratch coat has attained sufficient rigidity to receive the second coat.
Many experts believe this is beneficial to the plaster by providing a stronger bond between the two coats and enhanced curing of the scratch coat.
Brown to finish
IBC: 7-10 days, 14-21 even better to allow reentrant cracks (diagonal from corners) to form
Finish to paint - 7 days to allow ph levels to neutralize
1. cat face - two coats, rough then smooth with some rough showing through
2. dash - fine to rough but sprayed on with hopper for a kind of “popcorn ceiling” look
3. lace and skip - sanded finish with high points knocked down with trowel
4. sand float - most common finish
5. smooth finish - steel trowel
6. worm (aka: swirl, putz) - large aggregate leaves little grooves or “worm trails” when dragged by trowel
7. Santa Barbara - rustic uneven smooth finish
8. English - putty knife strokes
New stucco stuff
crack isolation mesh over brown coat
Latex finish coat
stucco penetrating sealers
national gypsum - Permabase stucco boards - $2sf less than traditional and faster
fluid air/moisture barrier
optional drain screen
staggered stucco boards and seam tape
base coat - fiberglass mesh crack isolator - 2nd base coat
- allows moisture to escape
- expansion joint allowing the wall to shrink and expand throughout the year because the stucco doesn’t stick to the slab
clean the crack and blow out the dust! not even professional grade caulking will adhere to dust
caulking - silicone best but not paintable
acrylic is paintable
sanded caulking for hairline cracks
10 lb box of rapid set stucco for surface retexturing with a sponge float, not a trowel
play with the sandiness and feather the edges - the wetter your float the more sand rises to the surface, the less the smoother it remains
Mineral salt deposits which form on the surface. Salts in the brick, stucco and mortar or in soil behind a retaining wall are dissolved when wet and carried to the surface where it recrystallizes
Dry brush efflorescence - DONT wash with water! Water redissolves the salt and puts it back into the surface
EC Pull Out organic acid crystal powder dissolves deposits that make leave visible stains
must fix moisture problem whether in or behind wall
verify vapor barrier is intact
use lime resistant screws to drill back to studs and patch
Mold, Moss, Staining
stucco is permeable and porous - things get washed in and embedded
sheathing - preferred
traditional siding - horizontal, batten board, shingle
contemporary - wood cladding on sleepers
fiber cement - needs a hardie blade and dusk masks
polymer, resin, composite siding
Warping and Buckling
This is a common issue for vinyl siding. Unlike wood siding, vinyl should not adhere tightly to the house. It should be fastened properly to allow for slight movement such as expansion and contraction as the temperature changes. If it is tightly attached, it may warp or buckle.
There are several reasons the siding cracks. One of them is physical damages caused by the heavy impact of falling tree branches, rocks hurled by a lawnmower, and the like. Additionally, if not properly treated, it may allow moisture to seep in, which could lead to mold growth. Exposure to extreme weather conditions may also cause the siding to crack due to contraction and expansion.
The main culprit for this problem is the sun. Direct exposure can fade or discolor the siding. Although this is not a problem resulting from improper installation, when not given attention, not only does it ruin the appearance of the siding, but it may also lead to more serious problems such as cracking.
One of the most important components of siding installation is waterproof barriers. They keep moisture at bay, protecting the siding and giving it extra room for expansion and contraction. If moisture is allowed to penetrate the siding, mold and mildew can grow. Rotting will follow next, destroying both the external and internal parts of the siding.
When the siding is installed improperly, it can create irritating noises whenever it contracts or expands as the temperature changes or during a windy day. Loose siding should be repaired immediately.