BC 11 Flashcards
fundamental safety points of roofs
usually not as strong as floors because they are designed to support lighter live loads
inherent concealed spaces between ceiling and roof deck, difficult to tell how much fire has developed overhead
over time loads may be added to roofs for which they weren’t designed
pitched roofs
low slope- up to 3/12 means for each 12 units horizontal roof slopes upward 3 units
medium to high slope-4/12-12/12
some churches or mansions have 18/12
gable roof
two inclined surfaces that meet at the ridge
hip roof
slopes in four directions, degree of slope like Gable roof
gambrel roofs
slope in two directions, break in the slope on each side
mansard roof
break in the slope on all four sides.
modern mansard has a flat roof deck
false mansard sometimes added to front of flat roof
butterfly roof
slopes in two directions
2 shed roofs thet meet at the low eave
monitor roof
monitor roof extends several feet above the roof. vertical sides usually contain windows known as clerestories
sawtooth roof
common in industrial for light and ventilation glass should face north
conventional roof framing
use inclined members to support types of pitched roofs that are built on site using dimensional lumbar
rafters
ridge boards
collar ties
ceiling joists and rafter ties
sizes of roof members
ridge beam usually one size larger than rafter
rafter- 2x4-2x14 spaced 12-24 inches apart
common roof truss
all chords and diagonal members in the same plane. typical of lightweight trusses
roof trusses
2x4 or 2x6 2-4 feet apart on center
should consider defensive attack
bowstring truss
split ring connectors at all joints except where heel meets ends of the truss
top chord-bow
bottom chord- string
roof deck
rolled materials
plywood
wood planks
correlated steel
precast gypsum or concrete planks
poured gypsum
poured concrete
cement planks containing wood fiber
wood planks
wood panel decking thickness of 1.2 inch on supports 24 inches on center
wood planks min 1 inch nominal thickness
correlated steel decking
29-12 gauge with depth from 3/4-2 inches
vapor barrier of flat roof coverings
reduce the diffusion of interior moisture into the insulation layer
built up roofing membrane
several overlapping layers of roofing felt saturated with bituminous material like tar or asphalt
single ply membrane
single membrane laid in sheets 10-20 ft wide and up to 200 ft long
most commonly synthetic rubber
ethylene propylene diene monomer (EPDM)
polyvinyl chloride(PVC)
chlorinated polyethylene (CPE)
fluid applied membranes
curved roofs or domes
neoprene
silicone
polyeruthane
butyl rubber
modern asphalt shingles
fiberglass based with mineral aggragate embedded on surface
12x36 inches
roof covering classification
class A: coverings are effective against severe fire exposure
B: are effective against moderate fire exposure
C: coverings are effective against light fire exposure
PV systems
photovoltaic roof
cell
panel
array system of panels
