Lath and Plaster vs. Drywall – Differences

At some point during the past century, drywall surpassed lath and plaster as the finishing material of choice for interior walls and ceilings. You may be wondering why this is the case- when plaster walls clearly look great and provide decent-if not great- insulation. To answer your question, we’ve written this detailed review of lath and plaster versus drywall.

What is lath and plaster?

Lath and plaster is a construction method used in finishing interior walls and ceilings. It consists of horizontal strips of wood (wood lath) coated with plaster. The wood strips are installed onto the joists, one above the other, with a gap of at least 9mm between them. Lath may also be built from extruded metal (metal lath) or stone (rock lath).

The gaps between the lath strips allow for plaster- a cement and cement-based building material- to be applied through them and form plaster keys that reinforce the structural strength of the wall. Once the plaster keys are firmly secured to the wall- which is usually after five days- you can then apply two more coats of plaster. Lath and plaster gained popularity in the building industry due to its excellent soundproofing capabilities.

Lath and Plaster vs. Drywall – Differences

Construction

Lath and plaster walls are made out of lath strips made out of wood, metal, or rock. Drywall- on the other hand features gypsum core construction- with the core being enclosed between two paper backings.

Durability

Plaster is a hardier wall finishing material compared to drywall. And that’s not all- it also performs better than regular drywall in terms of soundproofing, insulation, and fireproofing performance. Plaster blocks off sound transfer better than drywall since it is denser. However- modern soundproof drywall and fire-rated drywall perform just as well as lath and plaster walls in terms of noise dampening and ability to hold off fires, respectively.

Ease of Installation

It takes more time and effort to properly install plaster finish when compared to installation of drywall panels. Correctly applying plaster through the lath takes lots of time- as you have to wait for about five days for the plaster keys to set. By comparison- after hanging drywall sheets- it only takes 12-24 hours for each coat of joint compound to dry up.

Costs

The overall cost of a lath and plaster wall is usually higher than that of a drywall wall. This is mainly due to plaster walls being considered more high-end than drywall- especially in terms of visual aesthetics. Additionally, it takes longer to install plaster wall finishing, leading to higher installation costs if you don’t fancy DIY projects. There may not be any significant variances in material costs though, as the price of gypsum board panels and joint compound balances out against that of wood lath strips and plaster.

The table below provides a summary of the differences between lath-and-plaster and drywall, as discussed above:

Lath and plaster walls	Drywall walls
Made of wood strips coated with sand/cement plaster	Made of gypsum boards with paper backings, and reinforced with joint compound
Requires a lot of time and labor to install properly	Easier to install and doesn’t take as long as plaster finishing
Structurally stronger and denser than drywall material	Can’t match plaster in terms of hardiness or durability.
Costs more to install due to increased labor demands	Costs less to install due to shorter installation timeline.
Boasts decent insulation and soundproofing capabilities, as well as mold-resistance.	Traditional drywall can’t match plaster in terms of heat retention and noise cancellation, but modern drywalls may be equal to or better than plaster in terms of insulation and soundproofing qualities.

How lath and plaster walls are built

To build wood lath and plaster wall covering, wood strips that measure one-inch wide and four-feet long are nailed down to the open wall studs. The wood strips are tucked one above the other, with a tiny gap between them. The lath forms a backing structure for the wet plaster. Three layers of wet plaster is then applied to create a hard but smooth surface that can then be finished by priming and painting.

The first coat- also referred to as the scratch coat is usually hand-troweled onto the gaps between the lath strips to form the plaster keys. The plaster keys dry out on the inner side of the wood lath, forming grips that firmly secure the remaining layers of plaster onto the lath. The next coat- namely the brown coat- further levels out the finish. Finally, the last layer (white coat) is applied to form a smooth, flat surface ready for finishing.

How drywall walls are built

Drywall is made by mixing raw gypsum with crystalline water and other additives such as paper pulp, starch, and a thickening ingredient. The result is a thick paste that is then spread out on top of manila paper in layers that are between 3/8- 3/4-inch in thickness. Another piece of manila paper is then laid to form the upper backing. The material is then machine-heated to over 500-degrees Fahrenheit to dry it up.

Afterwards, the lengthy strips of dried wall finishing material are cut to size- forming what we refer to as gypsum boards or drywall panels. Drywall is so named because unlike wet plaster that takes a long time to dry, the wet work part of drywall construction is pre-done in the factory; and since it’s already ‘dry’, there are no long wait times when installing it. It’s for the same reason that drywall sheets can also be installed directly onto the wall studs, with no need for lath backing.  

Should you remove lath before drywall?

After some years, your plaster wall will start to show signs of wear and may come off in certain areas- causing unsightly patches. In such instances- a common solution is usually to switch to drywall. A common dilemma that many homeowners find themselves faced with when looking to switch from plaster walls to drywall walls is whether to remove only the plaster material or the wood lath backing as well.

While some remodelers may agree to install the drywall over the lath at a lower fee, we recommend removing the lath strips as well. This is because the wood lath may already be structurally compromised due to years of rot and may not form a strong structural base for your drywall panels. In addition, it’s easier to install insulation features and wiring through the wall when the lath backing isn’t obstructing access to the interior part of the wall.

Pros and cons of lath and plaster

Pros of Lath and Plaster

1. Excellent heat insulation– lath and plaster wall covering boasts great insulation capabilities, as plaster is a dense material. The fact that the plaster is applied in three layers helps with insulation as well. The thickness also helps with soundproofing.
2. Contour-friendly– when compared to rigid drywall panels, plaster can be more easily contoured into different shapes and designs. It’s- therefore- the preferred options if you’re going for elegant interior wall design that features curved and arched shapes.
3. Visually appealing– plaster wall finishing has a smooth and flat feel- making for a surface that can readily be painted to a high-gloss finish for enhanced visual allure.

Cons of Lath and Plaster

1. Plaster can Crack and fall off– plaster is a hard and brittle wall finishing material that will readily crack as they house settles with time. Severe cracking will lead to pieces of plaster falling off the wall, leaving behind ugly patches that dampen your home’s interior décor and need to be refilled.
2. Inhibits Future Wiring Upgrades– if you want to install new electrical or plumbing wiring, it’s hard to drive the cables or pipes through plaster and lath walls, as they contain fallen plaster at the bottom of the stud spaces that block wire passage.
3. Prone to Moisture Damage– if your plumbing system passes through the lath and plaster wall and develops a leak, the moisture will cause extensive rot of the wood lath. This will then trigger further structural damage, as the plaster may start to break away from the wood lath and fall off.

Pros and cons of drywall

Pros of Drywall

1. Easy to Install– perhaps the biggest advantage of drywall is that you can install it quicker and which much less effort than lath and plaster wall finishing. It’s for this reason that DIY enthusiasts prefer drywall over plaster.
2. Great fire resistance– drywall is made of gypsum mineral and crystalline water. When a fire outbreak occurs, the crystalline water evaporates and cools down the surrounding structure, preventing the fire from spreading to the rooms that are on the other side of the fire.
3. Cheaper to Install– since it’s easier and faster to hang drywall panels compared to installing lath and plaster wall finishing, professional drywall installation is more affordable than professional lath and plaster wall finishing.

Cons of Drywall

1. Appearance limitations– if not properly installed, the joints between the drywall sheets may be visible. What’s more, the visual aesthetic that drywall gives isn’t as alluring as smooth plaster walls.
2. Not durable– compared to plaster, drywall is less durable and will readily show unsightly dents and scratches. Nevertheless, you can easily repair drywall damage.

Is lath and plaster better than drywall?

The better choice between lath and plaster depends on what you’re going for and how much time you have on your hands. If you prefer interior walls with the kind of homely feel associated with pre-1940 homes, then lath and plaster is the way to go. Meanwhile, if you prefer wall covering that is affordable and can be installed quicker- then drywall is the better choice.