Construction Flashcards
low slope roof
less than 2” per foot or 17% (but above 1/4” per ft)
Relatively slow drainage, small errors resulting in ponding. Membranes must be flawlessly watertight. Water vapor from the building inside or wind from outside can cause blistering, flapping, displaced or cracked membranes, But can cover buildings of any horizontal scale, simpler geometry, can be planted & occupied
Steep roof
greater than 2” per foot or 17%
Use gravity to shed water, overlap small units (shakes, shingles, thatching, etc). These smaller units can be easily repaired and replaced, and bend and flex with the roofs expansion and contraction. However they are visible
way to slope the roof
- slope the structure
- taper the structure
- tapering the insulation
Topside Roof Vent
Allows moisture vapor to escape from beneath the membrane but closes to prevent water or air from entering
low slope roof membranes
- bituminous (made from asphalt, overlapping layers)
- single-ply (rolled up plastic that we unroll)
- fluid applied (take a chemical sealant and mop or spray it on)
Emissivity
ability for the roof to shed heat, high emissivity roof means it can shed the heat quickly so its cooler
Albedo
solar reflectance, high albedo is light color & reflective (we want atleast 65% albedo)
Difference in strength b/w springwood & summer wood
Summerwood - grows slower, more strength
Springwood - grows faster, less strength
modulus of elasticity
measure of overall strength / stiffness, higher number means stronger
Plain sawn
cheaper, more likely to warp, produces less waste
Quarter sawn
finer grain (better aesthetics), more dimensionally stable, more expensive
Moisture content (MC)
how much moisture is in the wood, the less moisture the greater structural quality
MC = ((Weight when wet - weight when dry)/Weight when dry) * 100
Ex. MC15 = 15% moisture, MC19 = 19% moisture, MC15 is stronger
Wood grades
Stud grades - for studs, including load bearing
#1 structural framing - for headers and long spans
Utility grade - for blocking, etc
glue laminated wood
layers of dimensional lumber bonded together with durable, moisture-resistant structural adhesives so that all of the grain runs parallel to the longitudinal axis
Cross-laminated timber
several layers of kiln-dried lumber boards stacked in alternating directions, bonded with structural adhesives, and pressed to form a solid, straight, rectangular panel
Lightweight yet very strong, with superior acoustic, fire, seismic and thermal performance, CLT is also fast and easy to install, generating almost no waste onsite.
Laminated strand lumber
dried and graded wood veneers, strands or flakes that are layered upon one another and bonded together with a moisture-resistant adhesive into large blocks known as billets
(longer strands) not super strong, inexpensive
oriented strand lumber
OSL is made from flaked wood strands that have a length-to-thickness ratio of approximately 75. The wood strands used in OSL are shorter than those in LSL. Unlike OSB, the strands in OSL are arranged parallel to the longitudinal axis of the member
Parallel strand lumber
Dried and graded wood strands are layered upon one another and bonded together with a moisture-resistant adhesive into large blocks known as billets
In the case of PSL, long strands (longer than those used in LSL) are laid lengthwise in parallel.
strong, heavy, relatively expensive
Wood i-joists
dimensional lumber with an OSL board in between, used in floors, roofs, etc
Laminated veneer lumber
an engineered wood product that uses multiple layers of thin wood assembled with adhesives
like plywood but thicker
wood plastic composites
weather resistant, less likely to shrink and warp more flexible
How to calculate board feet?
Board feet = (nominal width (in) x nominal ht (in) x length (ft)) / 12
nominal vs actual
1 - 5/4 = -1/4”
2 - 6” = -1/2”
8 - 12 = -3/4”
oriented strand board
strongest & stiffest of nonveneered panels
most common in subfloors and exterior sheathing
fiberboard
made from the smallest grain of wood (compared to OSB and particleboard)
best for interior uses
smoothest surface
sheathing rating # / #
roof spacing OC / floor spacing OC
ex. 32/16 means spacing of 32” OC for roof and 16” OC for floor
Plywood bond classifications
Exterior - for exterior use
Exposure 1 - can handle some water, etc, but not meant to be exposed to weather long term (95% of plywood)
When do you have to treat wood?
-Wood joists are less than 18” above grade
-Wood beams or girders are less than 12” above grade
-Plates, sills, or sleepers are in direct contact with masonry or concrete which is in direct contact with the earth
-Wood framing members or sheathing are less than 8” from the soil
Types of wood treatments:
Creosote - oil based, can’t be painted, very toxic, phased out
Pentachlorophenol - oil based, can’t be painted, on telephone poles
Chromated copper arsenate (CCA) - phased out in 2004 b/c arsenic
Alkaline copper quaternary (ACQ) - less toxic, can’t be used with steel fasteners b/c copper, approved for above ground, in ground, and in water
Copper boron azole (CBA) - less toxic, can’t be used with steel fasteners b/c copper, approved for above ground, in ground, and in water
Micronized copper - powder, more natural looking, less corrosive to other metals
Carbon based pti - less corrosive to metal fasteners
Disodium octaborate tetrahydrate (DOR) - above ground only, good against termites
Sodium borate (SBX) - above ground only, good against termites
Decay resistant wood
Very - black locust, red mulberry, osage orange, pacific yew
Slightly: cypress, catalpa, cedar, chestnut, white oak, redwood, black walnut
Balloon vs platform framing
Balloon - requires fire stopping,
Platform - Newer and more common now, shorter lumber, less prone to fire spread, can frame wall horizontally
Strategies for drainage @ the foundation
dampproofing / waterproofing
Overhangs
Drip edges
Sloping ground away
Gravel fill
Rim board or band joist
Sits on top of the header or floor below or foundation
Seals the open ends o the joists
provides surface for attachment of exterior insulation, cladding, and finish elements
Transfers some of the loads to the floor below
After the attic, this is the most likely place for insulation gaps & air infiltration
Ice guard
a mat under the shingles at the outermost edge of the roof to prevent ice or water from infiltrating the roof construction
attic vent ratio
IBC requires min vent area 1/150th of attic footprint or, if theres a vapor barrier, 1/300th
Which is stronger, cold rolled or hot rolled steel?
Cold rolled steel is stronger than mild steel
How does carbon content affect metal strength / brittleness?
the more a metal has, the stronger but more brittle
-cast iron is stronger than wrought iron b/c carbon content
depth to span ratio: beam
Beam depth is generally 1/20 the span, width is ⅓ the depth
depth to span ratio: girder
Girder depth is 1/15 the span, width is ⅓ the depth
depth to span ratio: open web
Open web is 1/20 the span
Roofs, lightly loaded floors, or closely spaced can be 1/24 the span
depth to span ratio: steel decking
Steel decking depth is 1/40 the span
depth to span ratio: triangular steel truss
Triangular steel truss depth is ¼ the span
depth to span ratio: rectangular steel truss
Rectangular truss depth is ⅛ the span
Type 1 cement
normal
Type 1A cement
Normal, air entrained. Tiny bubbles introduced to the concrete and those help with durability (freeze/thaw) and make the concrete more workable, Used for exposed concrete in cold climates
Type 2 cement
moderate resistance to sulfates. for coming into contact with groundwater or below grade in sulfate heavy soil.
Type 2A cement
moderate sulfate resistance, air entraining
Type 3 cement
high early strength concrete. useful for precast concrete, concrete block manufacturing, tilt up concrete, and anywhere we would want to strip the formwork soon after pouring
Type 3A cement
high early strength, air entraining
Type 4 cement
low heat of hydration. for massive structures like dams where there is so much heat of hydration
Type 5 cement
High resistance to sulfate attack
aggregate sizing rule of thumb
have the aggregate be less than ¾ the distance between rebar and less than ⅓ the depth of a slab
rebar naming convention
Rebar # refers to the 1/8ths of an inch in diameter
Ex. #8 rebar is 8/8” or 1” diameter
rebar grades
Grade 60 = 60k PSI, most common
Also comes in 40 & 75, use 75 for columns
rebar overlap
Overlap rebar at the ends by 30x the diameter or use reinforcing bar couplers
Prestressed concrete
is substantially “prestressed” (compressed) during production, in a manner that strengthens it against tensile forces which will exist when in service. This compression is produced by the tensioning of high-strength “tendons” located within or adjacent to the concrete
Pre-tensioned - mostly precast concrete
Post-tensioned - mostly cast in place
steps to pouring a slab on grade concrete pad
- Scrape topsoil off to reveal a more stable subsoil. if the subsoil is not stable you need to truck some in
- At least 4” inches of 1.5” crushed stone to make a capillary break. roll out plastic sheet for moisture barrier
- Formwork. Edge of metal or wood supported by in-ground stakes
- Welded wire reinforcing on chairs or bolsters, or concrete brick to prevent rust moving through
- Pour the slab
- Scree the slab to make level
- Keep damp for atleast a week
- Control joints every 15’
Control joint vs isolation joint
Control joint - extend parkway down the depth of the slab and are intended to limit cracking
Isolation joint - go all the way clear through the slab, used for expansion/contraction, seismic, vibration/noise isolation, or breaking up the irregular shapes of a building
concrete beam depth & width ratio
Width = 3 x height
one way slab depth
4” - 20” deep, 1/22 the slab, post tensioned 1/40 the span
two way slab depth
5” - 12” deep, 1/30 the span, 1/45 if post tensioned
drop panels depth
⅓ the span, ½ slab depth
waffle slab depth
3” - 4.5” (plus depth of dome/pan), 1/24 the span, 1/35 if post tension
concrete beams depth
1/16 the span, 1/24 if posttension
concrete girders depth
1/12 the span, 1/20 if posttension
pre-tensioned pre-casts concrete
compressive stresses induced by high-strength steel tendons in a concrete member before loads are applied will balance the tensile stresses imposed in the member during service
mortar type M
Highest strength. Use below grade, with high loads, or sever frost
mortar type S
exterior reinforced masonry, exterior load bearing masonry, veneers subject to seismic or high wind loads
mortar type N
general purpose, balance of workability and strength, non-loadbearing veneers and chimneys, interior load bearing walls
mortar type O
interior or non loadbearing uses
mortar strength pnemonic device
word “MaSoNwOrK”, every other letter lists them in order of high to low strength
modular brick size
3 ⅝ x 2 ¼ x 7 ⅝ , 3 stacks are 8” high
utility brick size
3 ⅝ x 3 ⅝ x 11 ⅝, use less mortar, making it stronger and less expensive wall
typical mortar height
⅜” is typical mortar height, ranges ¼” - ½”
FBA brick
facing brick - more variation insize and chippage (aesthetic reasons) (A nomaly)
FBS brick
facing brick - some variation in size and chippage (S tandard)
FBX brick
facing brick - more dimensionally uniform and less chippage (X act)
paving bricks
used for horizontal surfaces, superior freeze thaw resistance, lower water absorption rates
fire brick
superior heat resistance, uses a special fire clay mortar and thinner joints
MW brick
weather resistant, for exterior use but only in weather negligible area (M iami brick)
NW brick
interior only (N terior brick)
SW brick
used for underground applications, acceptable for any climate, toughest brick (S now brick aka best for outside)
Modulus of rupture
most important for determining a stones ability to accept metal anchor that hold them to buildings
Flexural strength
most important for stone’s resistance to wind
Compressive strength (stone)
most important for stone in load bearing wall
Strap anchors
anchor the mortar to the wall between courses of stone
Regular (dense) concrete
stronger, but heavier and poor thermal resistance
Lightweight concrete
uses lightweight aggregate, weaker but higher thermal resistance
Aerated concrete
admixture creates air bubbles in concrete, even higher thermal resistance but even weaker
most common CMU dimensions
8 x 8 x 16 or 7 ⅝” x 7 ⅝” x 15 ⅝”
water penetration in masonry
Double wythe concrete block with capillary break
Finished with stucco, special paints, or special coatings that provide water resistance
Made with water repellent concrete and water repellent mortar
Use in arid climates
types of water / air / vapor control layer
Peel & stick
Liquid applied (spray or rolled on)
Building wrap (Tyvek)
Only works if lapped, is only for rain or air not both
Tar paper
Have to be very careful when applying these sealants
Window sealing
Can be with self adhered membranes, fluid applied, or pre-manufactured rigid
Air barrier materials
Gypsum board, OSB (if sealed properly), house wrap (if taped), plastic membrane, peel and stick membrane, spray more, concrete, glass & metal, roof membrane
We want walls with high r value and low u value
thermal control
insulation has less thermal bridges when outboard of the structure
also shading, radiant barriers, low e, shiny rooms, thermal breaks, thermal mass
foam plastic insulation
water tolerant, air impermeable, includes expanded polystyrene and extruded polystyrene
All are used as water vapor and air barrier (need to be taped)
expanded polystyrene (EPS)
foam / plastic insulation, cheaper and more easily worked in field, good for underground
Extruded polystyrene (XPS)
foam /plastic insulation, more insulation per inch
Polyisocyanurate
foam / plastic insulation, cannot be used underground, less flammable
Closed cell spray foam (CCSPF)
foam / plastic insulation, continuous, exposed to water for long periods of time, can be used below grade
Open cell spray foam
foam / plastic insulation, interior only (no water), not a vapor or water or air barrier, better for noise insulation, less expensive, mold resistant, less insulative per inch than closed cell
Glass fiber insulation
Have self supporting and semi-rigid versions for exterior use, cannot be used as an air rain or vapor barrier, can serve as capillary break drainage plane, less expensive than foam, more fire resistant
mineral wool insulation
inexpensive, can be used in exterior, can be capillary break drainage plane, fire resistant
Classes of vapor retarder
Class 1: less than 0.1 perms
- Foil, thick polyethylene sheet, vinyl wallpaper, white boards
Class 2: 0.1 - 1.0 perms
- Some plywoods, some latex paints, kraft paper, rigid foam insulation
Class 3: 1 - 10 perms
Greater than 10 perms is vapor permeable
where do you place vapor control layer?
Vapor barrier on warm side of insulation
Warm climate - outside insulation
Cold climate - inside insulation
which climate zones need a vapor control layer?
Climate zone 1, 2, 3, 4a, 4b
- For above ground framed wall, can get away with no vapor control layer
Don’t use class 1 if humid summers
Climate zone 4c, 5, 6, 7,8
- Need vapor control on inside of insulation (interior side), use class 1 or 2
- Can use class 3 sheathing in zones 4c or 5 if there is vented exterior cladding and sheathing is greater
what will determine the diameter of a long skinny column?
For long and skinny columns that are not placed far apart, the diameter of the column will likely be controlled by buckling rather than the load from above
theoretical k value
higher k, more likely to buckle
Multiply by column length
Works for steel or concrete, recommended design k value is for wood
what is shear a function of?
length
what is the moment a function of?
length squared
what is deflection a function of?
length cubed
what typically controls beam size?
bending moment
between shear walls, braced frame, and moment resisting frame - what is most and least expensive?
shear wall - least expensive
moment resisting frame - most expensive (because you have to put extra bolts on each connection)
bending moment formula
M(max bending moment) = (w (load per ft) x L^2)/8
max bending stress formula
Fb = M (max bending moment in-lbs)/S (section modulus in^3)
what does the section modulus indicate?
how robust is the geometry of the beam
max moment formula for a simple beam with uniform load
max = (w x l^2) / 8
(will be given on exam)
