How Do We Renovate Those Plaster Walls?

The Morrell House has had all its plaster removed due to damage during its relocation several years ago. The remaining wood lath would need some repair before it could be replastered.

The Morrell House has had all its plaster removed due to damage during its relocation several years ago. The remaining wood lath would need some repair before it could be replastered.

By Dennis Sullivan
During our last Historical Society board meeting, we had a lively debate about the best way to renovate the interior walls of the Morrell House. This historic landmark is finally getting the work its been needing for so many years. While the city has kicked in money for materials and members of the King’s Harbor church are pitching in with construction savvy and labor, the Historical Society is obligated to fund the interior wall restoration. Thanks to contributions and donations from members and events, we do have a bankroll to work with, but money is tight and we have other purchases like lighting fixtures and furniture coming up.

To “do it right”, with new plaster according to standard preservation guidelines, will be costly, while the dry walling approach will save money, but, according to more scrupulous renovators, would remove an historic element of the old house.
Up until the about 1940, plaster was the wall material of choice for a wide variety of buildings and homes. Plaster provided a durable, versatile covering for curved and flat walls or ceilings over stone, masonry and wood framing. The finished plaster surface could be stenciled, painted, decorated, or wallpapered. It was strong, fire-resistant, and provided some sound barrier.

Ground limestone or oyster shells created lime, the material used for plaster until the late 19th century. At the end of that century, the mineral gypsum became a plaster material and was used in combination with lime until the early 20th century.

Gypsum plaster set faster and provided a harder finish so it eventually became the favored material. A good plastering job was made of three coats. The first two coats, scratch and brown, were coarse and were made up of lime putty and/or gypsum, aggregate, water and animal hair fiber for lime-based plaster. A final setting coat of lime and no fiber was used to provide a smooth, white surface.

Lath is a system for holding plaster to create the wall surface. It is nailed at right angles directly to the structural frame of the house in most cases. Narrow wood strips with spaces between them make up the lath at the Morrell House. The technique is to push the plaster through the space so it slumps over the lath and creates a “key” that holds the plaster to the wall. Other lath choices are metal and rock lath.

At the Morrell House, all the plaster has been removed due to damage during the relocation to Dominquez Park. The wood lath remains although some lath has been damaged or removed. There are four options available for renovating the walls.
Repair the existing wood lath and use traditional plaster techniques.

This is a preservationist first choice because it restores the historic character of the house’s walls. Unfortunately it is costly and time-consuming. Due to the amount of wall that needs to be plastered this was not a viable option for our project.
Cover the old wood lath with metal lath and plaster.

By using metal lath and three coats of plaster we can achieve the smooth, solid wall surface that was original to the house. While this is not an inexpensive option, it does meet preservation guidelines and skilled craftsman are available to do the work.
Use veneer plaster.

Similar to conventional dry wall, veneer plaster uses 4’x 8’ sheets of thin gypsum board called blueboard. After the specially papered blueboard is placed over the existing lath two coats of plaster are applied. The finished walls are smooth and don’t have the problems normally associated with dry wall like dimples and screws popping through. Veneer plastering can be slightly more expensive than standard dry wall but can be finished in less time and with less labor.

Remove the lath and use dry wall.
This is the modern option for both economy and speed. One disadvantage of dry wall is that the existing lath would need to be removed from the structural frame. And, there is a lot of lath in the Morrell House. Standard dry wall thickness also impedes on the wood trim “reveal” or the depth from the wall surface to the wood trim edge.

The majority of board members voted to plaster the walls over metal lath. The cost is higher than dry wall, but we decided we will raise the funds to finish the walls with plaster and to complete the other necessary Morrell House purchases. So, watch for upcoming Historical Society events and fundraisers this year which will go to funding those beautiful new plaster walls and light fixtures.