Plaster Concerns in North Carolina Historic Homes: Repair and Preservation

 
 

History of Historic Plaster

Like Bath’s famous Palmer - Marsh House in Bath, NC (c. 1744, shown left), North Carolina’s historic homes have walls of wood lattice strips and a mix of lime and sand as the covering plaster.  This combination makes a durable and lasting structure. The natural swelling and shrinking of the wood over seasons moves in unison with hydraulic lime and sand that remain breathable with the lattice base.  However, along the eastern U.S., many structures are built over hard clay rather than stone.  Over time, shifting and settling in the ground occurs due to expansion and contraction of clay soil.  With foundations less thick or deep along the east coast, owing partly to milder winters, homes settle with the soil beneath them, often causing shifting in the walls, especially in the corners. Unexpected twisting, even breaking of the lattice within the walls can occur then, displaying  surface cracks and separation from the lattice base.



Understanding Plaster Repair Process


Step 1: Assessment

  1. To begin, an assessment identifies the cause of damage to walls.  If structural, whether from ground shifting or roof leakage, support of some type must be made to ensure repairs will be effective and lasting.  Cracks and backing support are evaluated to determine what repairs can be completed with the existing lattice and where new, metal lattice is needed to gap destroyed or deteriorated areas.


  3. The assessment is completed with the client and Edward Rokosz going over the estimate and determine the plan of action to assure that the historic property is preserved for every situation existing within the historic walls.





For example: In this wall (left), discoloration indicates long term water damage within the wall.  Raised areas in the plaster are not plaster separating but a specific mold compromising the plaster.








Step 2: Reconstruction

Reconstruction first involves removing the damaged area down to support structures.  Due to the historic value, as much of the original lattice is preserved, even when warped or broken, and metal lattice strips are used to brace earlier materials where needed.  With the wall’s strength and solidity returned, the surface is ready for a scratch coat.


Step 3: Applying Scratch Coat

Step 4: A mixture of hydraulic lime, sand, and water creates a “mud” which is applied to the wall and squeezed between the lattice strips.  This “keys” the wall, which means the globules of mud extruding between the lattice literally “lock” the lattice together with plaster and give the wall its solid, limestone-like base.  The lime and sand mixture will expand and contract with the lattice during future seasons and temperature shifts.  They will continue to breathe together.


  1.       WARNING! Why cement or gypsum can’t be used.

  2. A note here: Cement, dry wall or gypsum, used in modern construction, destroys the original wall by not breathing with the expanding and contracting wood as an authentic plaster does. Severe warping and breaking occurs within the original structure, and more severe damage occurs from using modern wall construction. In the end, a less expensive repair becomes very costly for the homeowner.


Step 4: Applying Brown Coat

The brown, or second, coat applied to the wall unifies the wall into one solid structure and provides an even base upon which the finishing coat can be applied.  The “mud” mixtures differ essentially with each of the coats owing to the relationship they have for structural support and protective coating.


Step 5: Applying Finishing Coat

The finishing coat contains two applications.  The first provides a fine, finishing surface, much like a slip applied to pottery, and the second establishes texture so the repairs match the wall’s original surface texture.  In new wall construction, Rokosz encourages homeowner to uniquely color these coats and avoid the next step.


Step 6: Painting

Unlike with cement or gypsum,  painting over original plaster can occur only after extended drying time.  Additionally, the walls are sealed and fixed with an alcohol-based primer before the room’s decorative coats can be applied. With new wall construction, this step is avoid by coloring the finishing coat.



The Process Complete

Restoring a wall to its original structure and provide your home or historic structure the preservation required to maintain its value.  Likewise, construction a new wall with original plaster provides you value beyond the hollow sounding walls of contemporary construction.



Copyright (c) 2007 by Kirk Hathaway (www.hathawaysites.com).  No words or images on this site may be used or duplicated without the expressed permission of the author or the artist Edward Rokosz. Please share with us your experience with this site and any inquiries you have.

 
Poland native Edward Rokosz makes North Carolina home creating sculpture, art and utilizing old world skills to restore and preserve historic homes and structures.