TM 5-852-9/AFR 88-19, Vol. IX
e. Temporary roofing. Where it can be predetermined that a complete permanent roof cannot be applied
because of weather conditions, temporary roofing should be applied directly to the roof deck. The temporary
roofing should not be incorporated in the final roof design.
2-4. Roof slope.
a. Dead-level roofs. Dead-level roofs are not permitted. Water does not drain off of a level roof when
the roof drain is surrounded by ice or snow. Also, deflection in mid-span often creates a point lower than the
drain. All membrane roofs tend to have inherent shallow ponds that do not drain well without adequate slope.
b. Sloped or pitched roofs. As a result of a report by the Alaska Roofing Board, sloped roofs from 1
on 12 to 4 on 12 have been adopted since 1957. Plate roofs should not be used in cold regions because snow
or ice accumulation in valleys causes leaks and other problems. A slope which will provide positive drainage
and prevent ponding should be used. A steep pitch on large roof areas produces a high attic which may not
be desirable. A slope of 1/4 inch per foot is the minimum recommended for built-up and elastomeric roofing.
For protected membrane roofs, the design roof slope should be 1/4 inch per foot to minimize ponding,
prevent creep of membrane and pavers, and limit parapet height. The maximum slope for built-up roofs is
3 on 12. The minimum slope for metal roofs is 1 on 12. Regardless of degree of slope, crickets, fill, or similar
means should provide positive drainage to roof drains in all directions. Basic roof slopes should be built into
the structural roof framing system whenever possible. Tapered insulation has been used selectively to produce
adequate drainage on rehabilitation and new projects.
c. Roof drains and gutters. Gutters on eaves and exterior downspouts should not be used on buildings
in arctic and subarctic regions because of snow and ice accumulation. In subarctic areas, interior roof drains
are normally used on buildings having large roof areas [see paragraph 4-6b,(2)]. Whenever feasible, overflow
scuppers should be used through the parapet walls. The bottom of the scupper should not be lower than the
roof drain. Scuppers should not be located above doorways. If scuppers cannot be provided, overflow drains
should be located up-slope from roof drains and connected to a separate drain leader. Overflow drains,
however, are not as effective as scuppers and should be used only where scuppers cannot be provided
(example: roof area isolated from an exterior parapet wall).
2-5. Exterior painting.
a. General Because of the extreme temperature variations in arctic and subarctic regions, paints should
be flexible enough to contract and expand with the substrate. TM 5-618/NAVFAC MO 1 10/AFM 85-3, and
the "Steel Structures Painting Manual," published by the Steel Structures Painting Council, are good
references. Whenever possible avoid the need for exterior painting by using materials that do not require
painting in the field such as natural, pre-finished, or integrally colored materials. Latex base paints perform
better on exterior wood than oil base paints because they breathe and thereby allow passage of vapor through
the paint which may avoid blistering.
b. Ambient temperature. Exterior paint is usually applied when the structure is nearing completion, often
late in the construction season. At this time of year, the night temperatures frequently fall to 40E F and below.
Such low temperatures do not allow proper curing, and the result will often be poor adhesion, poor strength,
permanent tackiness, or excessive wrinkling. This problem should be considered when planning the
construction schedule; for example, the exterior painting could be performed the summer following
construction. Paint may be cured during unfavorable weather or temperatures by providing properly heated
and vented enclosures where proper curing temperature is maintained.
c. Areas for special consideration. Major paint damage occurs where glaciation forms on exterior wall
surfaces from defective eave flashing, around exhaust louvers, and where water vapor leaks from within the
buildings. Wall glaciation, which results from melted snow on the roof through defective eave flashing and
moisture condensed around exhaust louvers, will cause removal of paint film and unsightly discoloration. The
paint film will break and blister on exterior wall surfaces where there is poor water vapor exfiltration control.
Moisture penetrates the paint film, prying it loose from the substrate. Designers should consider these
problems during design to eliminate the causes of glaciation, or provide finishes that do not require painting,
such as glazed structural units, clay tile, stucco, stone, mineral-surfaced colored non-asbestos panels, metal
siding with factory finish, CMU, or concrete. Water can get behind and freeze, then dislodge finishes such
as tile, stone, etc. This problem should be addressed in the design. Exhaust louvers and fans should be located
away from fire escapes, entrances, landings, etc., to prevent glaciation on these areas.
2-6. Caulking. Caulking compounds normally used in temperate regions do not perform satisfactorily in
arctic or subarctic areas. The extreme variation between low and high summer and winter temperatures
2-6
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