Interior Walls and Ceilings

Don’t make the mistake of assuming anything about the level of security afforded by interior walls and ceilings.

To assess the vulnerability of interior walls and ceilings in Forest Service offices, you need to ask some questions and make some observations.

• Do the walls between the Forest Service office space and the public corridor extend from a true floor to a true ceiling? Do the walls between the Forest Service office space and an adjoining tenant extend from true floor to true ceiling? Often they do not, because the space above the ceiling is used to carry utilities and fire suppression systems throughout the building. Often, that space is used as a return air plenum for the building’s heating, ventilation, and air-conditioning (HVAC) system.
  
  
• What is the construction of the ceiling in the public corridor outside the Forest Service office space? Is it a “hard” ceiling or is it a suspended ceiling? Do accessible hatchways allow someone to gain access to this space from the public corridor, from passenger elevator landings, from freight elevator landings, or from building utility closets? What prevents someone from entering the ceiling in the public space and going over the wall and entering Forest Service space through a suspended ceiling?
  
  
• What is the construction of the walls between the public corridor and the Forest Service space? Between neighboring tenants and the Forest Service space? In many commercial buildings, interior perimeter walls are single- or double-layer wallboard (also know as plasterboard, dry wall, gypsum board, or the trade name Sheetrock) mounted on wood or metal studs. Wallboard is available in thicknesses up to 5/8 inch. Wallboard can be cut easily with a dry wall handsaw.

Ideally, you want Forest Service office space with interior perimeter walls extending from a true floor to a true ceiling that cannot be easily or quietly cut open with handtools such as a dry wall saw. If certain rooms require higher security, the walls of those rooms should have similar construction. Any openings required for utilities or ventilation between the room’s ceiling and the true ceiling should be secured to inhibit unauthorized entry.

Expanded steel mesh can be installed over the inside studs of rooms on the perimeter of Forest Service space and of rooms requiring higher security. The mesh, which must be installed from the true ceiling to the true floor, will dramatically increase the time, sophistication of tools, and noise required to gain access. If mesh is used, it should be at least 13 gauge steel and should be screwed or bolted at least every 12 inches to each stud it contacts. Mesh seams must overlap. If the mesh overlaps between studs, the seam should be welded at least every 12 inches.

The advantage of expanded steel mesh is that if the area above the suspended ceiling is part of the return air plenum, no special ventilation openings are required. Expanded steel mesh does nothing to deaden sound. Expanded steel mesh is available in large sheets, however the sheets require more installation because they are time-consuming and noisy to cut. Installing wallboard over the expanded steel mesh is somewhat slower than installing wall board over bare studs.

The bottom line is that interior walls and ceilings require precautions to reduce their risk to penetration by force or covert entry. Often, normal installation and construction fail to use the proper precautions.