Here are a few things out of 2015 IBC, but you will most likely need to read thru the IMC or what ever plbg. & mech codes you are under. Generally it needs to have a CLEAR opening for the largest piece of equip. to be removed.
SECTION 1209
ACCESS TO UNOCCUPIED SPACES
1209.1 Crawl spaces. Crawl spaces shall be provided with
not fewer than one access opening that shall be not less than
18 inches by 24 inches (457 mm by 610 mm).
The requirements of this section establish 18 inches
by 24 inches (457 mm by 610 mm) as the minimum
size opening for crawl spaces. If access is through a
wall, the 18-inch (457 mm) minimum would be the
height and the 24-inch (610 mm) minimum would be
the width.
Items such as plumbing and wiring installations
pass through crawl spaces at times. Required initial
and periodic inspections, and repairs cannot be carried
out without access to such crawl spaces.
1209.2 Attic spaces. An opening not less than 20 inches by
30 inches (559 mm by 762 mm) shall be provided to any attic
area having a clear height of over 30 inches (762 mm). Clear
headroom of not less than 30 inches (762 mm) shall be provided
in the attic space at or above the access opening.
Access to the attic provides a convenient and nondestructive
means for fire department personnel to visually
check for an attic fire and, if need be, gain entry
to the concealed spaces and suppress a fire. Access
to attic spaces can be provided through the ceiling
within each compartment that is created by draftstops
or through openings within the draftstops themselves.
Openings located within the draftstop are required to
be self-closing and the opening protective must provide
structural fire integrity (the ability to remain in
place) similar to the draftstop. Access is required
when the attic space has a clear height greater than
30 inches (762 mm) measured from the top of the
ceiling joists (or top of the floor sheathing, if present)
to the underside of the roof rafters.
1209.3 Mechanical appliances. Access to mechanical appliances
installed in under-floor areas, in attic spaces and on
roofs or elevated structures shall be in accordance with the
International Mechanical Code.
Access to mechanical appliances is needed to maintain
and service the equipment. See Section 306 in
the IMC for detailed requirements.
1011.12.2 Roof access. Where a stairway is provided to a
roof, access to the roof shall be provided through a penthouse
complying with Section 1510.2.
Exception: In buildings without an occupied roof, access
to the roof shall be permitted to be a roof hatch or trap
door not less than 16 square feet (1.5 m2) in area and having
a minimum dimension of 2 feet (610 mm).
The purpose of the penthouse or stairway bulkhead
requirement in this section is to protect the walking
surface of the stairway to the roof. The exception provides
for situations when roof access is only needed
for service or maintenance purposes, and where the
access may be permitted by alternatives such as
alternating tread devices, ship’s ladders or ladders
1011.16 Ladders. Permanent ladders shall not serve as a part
of the means of egress from occupied spaces within a building.
Permanent ladders shall be permitted to provide access to
the following areas:
1. Spaces frequented only by personnel for maintenance,
repair or monitoring of equipment.
2. Nonoccupiable spaces accessed only by catwalks,
crawl spaces, freight elevators or very narrow passageways.
3. Raised areas used primarily for purposes of security,
life safety or fire safety including, but not limited to,
observation galleries, prison guard towers, fire towers
or lifeguard stands.
4. Elevated levels in Group U not open to the general public.
5. Nonoccupied roofs that are not required to have stairway
access in accordance with Section 1011.12.1.
6. Ladders shall be constructed in accordance with Section
306.5 of the International Mechanical Code.
Permanent ladders are permitted as a means of
ingress and egress to very limited spaces. Typically,
these spaces are not considered occupied and, as
such, are not required to have a means of egress.
While the term “technical production areas” is not
used in this section, Section 410.6.3.4, Item 6, allows
for ladders to be used to access technical production
areas. Item 6 of this section references the IMC for
when ladders can be used to access mechanical
equipment that is located in an elevated space or in a
room. The details and construction requirements for a
permanent ladder are also found in that section. This
will help make sure that permanent ladders are safe
and useable, while providing consistency for both the
designer and the building official.
