Protection of Historic Interior
Features and Finishes
An important difference between protecting historic interior features and finishes and protecting new interior features and finishes during construction is in the timing of the construction schedule. In new work, important and fragile casework and finishes are installed late in the construction schedule, after mechanical and electrical systems and other high impact work are completed, thus not exposing the finishes to major construction operations. In preservation work, however, existing interior finishes are exposed to all the high impact and potentially damaging construction phases of the project, except to the extent that such finishes are temporarily protected or separated from construction work.

Important architectural features which are easily removed should be stored off site, if possible, to protect them from vandalism, theft and damage during construction. Lighting fixtures, fireplace mantels, and interior doors are typical examples. Less movable architectural material or finishes such as wallpaper are often best retained in place but may require custom-designed protective measures developed and monitored by a conservator (see figure 3).

Access by construction personnel to spaces with significant features and finishes should be restricted, except for their work relating directly to the preservation of such spaces. Spaces with restricted access should be identified by the planning team and indicated in the construction documents in order to allow the contractor to include any associated costs in his price proposal (see figure 4).

For spaces such as halls and lobbies, it may not be practicable to limit access, and for all interior spaces, some construction work may be required. In such circumstances, interior finishes must be physically isolated from construction operations by means of protective barriers and coverings. Such surfaces are generally limited to flooring, walls up to approximately 6 foot height, and special construction such as staircases. Only under unusual circumstances do ceilings or upper wall areas require physical protection during construction. Examples are walls with historic wallcoverings or fragile ornamental ceilings that are at risk to physical abuse or to vibration damage caused by construction activities.

Figure 3B

Flooring should be protected from damage caused by abrasion, falling objects, dust and dirt, and spilled liquids (see figure 5). lf work in, or traffic through, a particular space does not involve one or more of these risks, temporary protection may be reduced. Damage caused by abrasion can be controlled by means of protective coverings such as canvas tarps or resilient wood fiber panels. Canvas tarps should overlap and be taped at all joints. Resilient wood fiber panels should be carefully fitted with tight seams and laid continuously wall to wall. Joints should be taped to avoid displacement of the panels after setting. For added safety, resilient panels left exposed should also be fire-retardant treated to achieve a UL Class A listing for flame spread and smoke developed. Such a readily available product is N.C.F.R Homasote.

For greater protection from physical force, a layer of plywood can be applied over the Homasote panel underlayment, with joints staggered to stabilize the assembly. In this double layer assembly, the top plywood should be treated with a fire-retardant, but the underlayment need not be. Where protection from spilled liquids is required, a layer of polyethylene sheeting should be applied between the Homasote panels and the plywood top layer. Care should be taken in planning the protection assembly to ensure that moisture from spilled liquids is not trapped against the historic flooring.

Figure 4. Temporary protection during construction can involve covering historic features, such as floors and walls, as well as using temporary doors to control the passage of workers and the inevitable dust and dirt. Prominently located fire extinguishers are mandatory. Photo: Annie Hover, AIA,The Octagon.

Otherwise, the staining, splitting, wood-grain raising, or stone-finish destruction could potentially go undetected for months while concealed from view under the protection assembly. Care should also be taken to avoid sheet coverings such as building felt, which could potentially stain the historic flooring.

Wall protection is typically fabricated from fire-retardant treated plywood attached to wood framing. The assembly should be self-supporting and self-bracing, secured at its base to the floor protection assembly. Struts and walers need to be provided, as required, to brace the assembly without installing fasteners into the historic wall finish. Careful assembly includes using screw fasteners in order to eliminate hammering during assembly and ripping damage during disassembly. Where wood framing, furring, or panels abut historic wall materials, the back side of the protective assembly should also be padded using strips of neoprene or strips of Homasote board, glued to the protective assembly member.

Historic stairways, balustrades, balconies, fireplaces, door surrounds, window surrounds, and other components will also need to be protected from construction damage by combining the techniques described for floors and wails (see figure 6). Horizontal surfaces should be protected as floors, and vertical assemblies treated as walls, with the major difference being the complexity of the framing required.