or ceiling structure (but only within original suspended or
furred ceiling); between structural sub-floor and flooring
(within non-structural fill or between sleepers); exposed in
cellar, bottom floor, and crawl space (in service areas only);
trenching below building (if soil and groundwater conditions
permit); within walls (in existing furred spaces or new built out
spaces) ; within furring over structural members; above beam
flanges, on top of cornices or other concealed locations. Do not
cut away portions of historic woodwork or cornices to install new
When installing water pipes, electrical conduits, and ducts,
be careful not to cut through beams and floor joists, especially
near the bearing or in the upper and lower third of the member.
While the floor or ceiling is open, inspect and repair bearing
members that have been undermined by earlier plumbing
installations. Reinforce weakened members with wood or steel
Security and fire detection and suppression systems can often
be installed using the same precautions.
The use of fan-coil air conditioning units to cool rooms may
be desirable. They require only piping installation in the
historic fabric, and they can be located unobtrusively beneath
windows and painted to match wall finishes. Through-wall room
air conditioners should be avoided. If window units must be
used, they should be mounted on side or rear walls, and wall
surfaces should be protected from dripping condensation. For
Vibrations from air-conditioning condensers and other
machinery may be harmful to old structures. Special care is
required to dampen vibrations in attic and roof-mounted
equipment. Do not suspend systems from attic roof rafters.
Roof-mounted air-conditioning systems should be located so that
they cannot be easily seen from the ground.
You may occasionally come across historically interesting
mechanical equipment or decorative elements in unlikely places.
These items could be marble counters and stalls in bathrooms,
brass or bronze lavatory faucets, door handles, or stall
connectors. These should be preserved and used where they are,
Be alert for corrosion and leaks in piping systems over 30
years old. Maintain valves, such as radiator valves, and replace
seats and rings every few years. Install water hammer arrestors
as needed to prevent vibration. Maintain traps and air vents on
steam systems to keep condensate from fountaining from the vents
when the system starts up. Maintain water treatment systems to
prevent corrosion in piping.