Lecture 21

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Arch 330
Thermal & Moisture Protection
Roofing Systems
Roofing Systems
073000 Steep Slope Roofing
Shingles and Shakes
Roof Tiles
Natural Roof Coverings
074000 Roofing and Siding Panels
Roof and Wall Panels
Siding
075000 Membrane Roofing
076000 Flashing & Sheet Metal
077000 Roof and Wall Specialties and Accessories
Division 7
078000 Fire and Smoke Protection
079000 Joint Protection
Joint Sealants and Expansion Control
Low Slope - Disadvantages
• water drains slowly
• standing water can cause deterioration
• structural movement - tear the
membrane.
Low Slope - Advantages
• can cover building of any horz. dimension
can serve as
• balconies, decks, patios, landscaped gardens.
Item Spotted: Flat roof
Observations: This is not a
good roof design for wet
climates. There is constantly
puddles of water on the top
of this roof.
Location: PEB, WSU
Campus
Name: Kallen Hawthorne
ID# 10596914
Steep Slope
• drains quickly
• can be covered with roofing material of
small overlapping units
- shingles of wood
- slate
- artificial composition
- tiles of fired clay or concrete
- bundles of reeds (thatch).
Steep Slope
• Thermal expansion / contraction minimized
• Movement in structure is minimized
- by the ability of small units to move with
- respect to one another.
• Water vapor vents from the interior through
the loose joints in the roofing material.
Item Spotted: A
combination of a flat and
gamble roof
Observations: This
building has a very
interesting skyline because
of the combination roof.
However if one was to
look closely at the picture,
one con see puddles of
standing water.
Location: Smith Gym,
WSU Campus
Name: Kallen Hawthorne ID# 10596914
LOW SLOPE ROOF
(not FLAT) < 3:12 pitch
• Min Slope
• 1/8” per 1’-0” or 1:100
• 1/4” per 1’-0” or 1:50
Low < 3:12 pitch
3
1/4
12
Roof Slope
• Slope Roof to direct water towards drainage
points
- counter-acting structural deflection.
• Depending on size of deck expansion joints
should be provided to
- control expansion and contraction and
- satisfy requirements of membrane.
• Membrane should be laid on flat surface.
FLAT ROOF - COMPONENTS
• DECK
• THERMAL INSULATION
• VAPOR RETARDER
• MEMBRANE
• FLASHINGS
• DRAINAGE COMPONENTS
Deck:Types of structural deck
used for low slope roof
•
•
•
•
Plywood over wood joists
Solid wood decking over heavy timber framing
Corrugated steel decking
Panels of wood fiber bonded together with
portland cement
• Poured gypsum over insulating formboard
• Sitecast concrete and precast concrete
Insulating Deck Boards – wood/glass fibers
Truss Tee Purlins + slab of gypsum/lt wt conc
Thermal Insulation
• Below the Deck
• Between Deck + Membrane
• Above the Membrane
Thermal Insulation:
Below the Deck
• Leaves the deck and membrane exposed to
full range of temperature.
• Batt insulation of glass fiber or mineral
fiber between wood joists
- or on top of a suspended ceiling assembly.
• Vapor retarder below insulation**
(Vapor retarder on warm side of insulation)
Insulation: Between Deck and
Membrane
• Rigid panels of insulation, light weight concrete.
• Protects deck from temperature extremes.
• Membrane subjected to extreme temperature
variations.
• Moisture trapped in insulation can damage
insulation and deck.
• Place vapor retarded on inside of insulation and
vent insulation to release moisture.
Insulation: Above the Membrane
• Membrane protected - extremes of temperature.
• Membrane on warm side of insulation - immune to
vapor blistering.
• Insulation must be a material which is not effected
by wet and will not disintegrate - extruded
polystyrene board
• Insulation board adhered in bed of hot asphalt or
laid loose.
• Layer of ballast laid over insulation.
Insulation: Above the Membrane
• Ballast
- crushed stone
- thin concrete layer factory laminated to upper
surface of insulation board
- interlocking concrete blocks.
• Membrane ages little protected from sunlight and
temperature extremes - despite presence of
moisture.
• Rigid insulation - mechanical fix to deck
preferable.
Insulation above the Membrane:
Other names for this system
• Inverted roof
• Upside down roof
• Protected membrane roof,
+- 20years old
Vapor Retarder
• 2 sheets asphalt saturated roofing felt
• In cold climate on warm side of
insulation.**
• In hot humid climate/with air conditioning on outer side of insulation**
Membrane
• Built up roof membrane
• Single-ply roof membrane
• Fluid-applied roof membrane
Built-up membrane
• 2-4 Layers/ plies of felt
asphalt impregnated, bedded in bitumen
felt: cellulose fibers/glass fibers +asphalt
• Felt laminated in overlapping layers
• Layer of aggregate (crushed stone)
Built-Up Membrane
• Bitumen - asphalt derived
• For low pitch roofs - coal tar bitumen or
coal-tar pitch used- greater resistance to standing water
• Asphalt and coal tar are applied hot
•
•
•
•
Aggregate
Insulation
Felt
Conc. Deck
•
•
•
•
Aggregate
Felt
Insulation x 2
Metal Deck
• 4 ply felt + hot asphalt
Single Ply Roof membrane
• Single layer
• More elastic - less cracking/tearing
• Fixing: adhesives, ballast,
concealed fasteners, mechanical
fasteners.
• Protective coating
Single Ply Roof Membrane
• EPDM , synthetic rubber
(ethylene propylene diene monomer)
• NEOPRENE (polychloroprene)
synthetic rubber compound
• PVC (polyvinyl chloride)
vinyl - thermoplastic compound
Single-Ply Membrane
Aluminum Faced
Single-Ply Membrane
Fluid Applied Membrane
• domes, vaults, complex shapes
• roller or spray gun, applied
• several coats - rubbery membrane.
Built-Up + Single Ply
Ballast
• loose stone aggregate
• precast concrete blocks.
• Ballast holds the membrane in place against
wind uplift
• Protects membrane from ultraviolet light
and physical wear.
• Increase the fire resistance of the roof
covering.
Traffic Decks-walks, terraces,
parking – on low slope roof
(a) Heavy square paving slabs or stones –open joints
on blocks of plastic or conc on roof membrane
(b) Open Jointed Paving Blocks on A drainage layer
of gravel or porous concrete leveled over the
membrane
•
•
Water falls through the joints and is drained away
by the membrane below
Membrane is not pierced.
Structural Standing Seam
Metal Roofing for Low Slope
Roofs:
• Proprietary systems of standing seam metal
roofing
• Used as low slope roofs - 1/4" in 12 "(1:48).
• The folded shape - stiffness - support itself +
a normal snow load between purlins without
the need for structural deck below.
Mechanical Fix
Through Insulation to
Deck below
Hot Application of
Layers
Stone ballast on Insulation on Membrane
Mechanical Fix
Steep Slope >3:12 pitch
11.25º
3
12
Steep Slope >3:12 pitch
• Drains quickly,
• Small overlapping units - Shingles
• Expansion and contraction and
movement
• Water vapor vents
Steep Slope Roof – Systems
3 Categories of Covering
• Thatch
• Shingles – wood, asphalt, slate, clay/conc
• Sheet Metal – lead, copper, terne, aluminum
Steep Sloped Roof Systems
• Typically insulation and vapor retarder
installed below the roof sheeting or deck.
• Underside of deck is exposed as a finished
surface
- vapor retarder and rigid insulation above
the deck below roofing layer of plywood
(nailed over the insulation panels as a nail
base for fastening shingles or sheet metal).
Insulation
Steep Sloped Roof
Typically insulation and vapor
retarder installed below the roof
sheeting or deck.
Insulation
Steep Sloped Roof
Underside of deck is exposed as a
finished surface
Flashing @ all
junctions
Thatch
•
•
•
•
•
•
Bundles of reeds, grasses or leaves,
Labor intensive
Highly insulative
Attractive
Codes limit its use
Not fire resistant
Shingles
Small size unit, applied to roof in overlapping
layers - staggered vertical joints
•
•
•
•
•
wood shingles/ shakes
asphalt shingles
slates
clay tiles and concrete tiles.
PV – photovoltaic
Shingles
• Each type of shingle, slate or tile must be
laid on a roof deck - that slopes sufficiently
to assure leak-proof performance.
• Min. slope for each material are specified
by the manufacturer and code
Wood Shingles:
• Thin, tapered slabs of wood, SAWED from
short pieces of tree trunk
• Grain parallel to the face of the shingle.
Wood Shakes
• Split not sawn
• Rough face texture,
• North US - wood shingles/ shakes are Red
cedar, White cedar,
• Redwood - natural decay resistance.
• Wood roof covering moderately expensive,
not highly resistant to fire unless pressure
treated with fire retardant chemicals.
Asphalt Shingles
• Asphalt impregnated felt - faced with mineral
granules.
• Die cut from sheet, typical size 12" x 36".
• Slotted twice - smaller unit.
• Inexpensive, quick to install, moderately fire
resistant.
• Expected life time of 15 to 25 years.
• Laid on asphalt saturated felt paper in two layers.
Slate
• Split, trimmed to size and punched or
drilled for nailing.
•
•
•
•
Fire resistant,
long lasting,
relatively expensive,
laid in over lapping layers.
Tiles – Clay, Concrete
•
•
•
•
•
•
Glazed and unglazed
Concrete less expensive than clay roof tile.
Typically heavy
Durable
Highly resistant to fire
Expensive in first cost
Architectural Sheet Metal
Roofing:
• Relatively high in first cost
• Last for many decades.
• Galvanic action should be avoided in the
roof installation.
• Beware of water run-off also re galvanic
action from one metal to another.
Seaside, Gulf Coast – The Truman Show
Strawbale, Potlatch, Idaho
Lead, Copper: Sheet
• Used since ancient times.
• Self-protecting metal - last many decades.
• Installed in sheets using systems of joining
and fastening
• Maintain water tightness at the seams.
• Seams especially standing & batten seams
create a strong visual pattern.
Lead, Copper: Sheet
• Lead oxidizes to a white color.
• Copper turns blue-green in clear air, black
in an industrial atmosphere.
• Chemical treatments and coatings can be
applied to preserve a desired color.
Other Sheet Metals
Aluminum,
Zinc Alloys,
Stainless Steel Sheet Metal Roofing
• Can be used in same way as copper, lead
and terne
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