wood construction Flashcards
difference between softwood and hardwood
softwood - large vertical cells - small % of radical cells
hardwood - small vertical fibers -large % of radical cells
considerations of sustainability in wood construction
- wood is the only major structural material that is renewable
- basic form of forest management
- — clearcutting and replanting (biodiversity ecology problem)
- — sustainable forestry (most recommended
FSC-Certified
forest stewardship concil
drying wood
klin - using large amount of fuel - high energy consumption - faster process
air - uses sunlight and wind - removing moisture at a slower pace
construction process - site waste
- design with full standard sizes of lumber and wood panel materials
- prefabrication
indoor ari quality (AQ)
- adhesive and binders cause serious VOCs such as formaldehyde
- some paints, varnishes, stains, and lacqers emit fumes unhealthful
- in damp locatioiins, mold and fungi may grow
building life cycle
- fire: provide smoke alarms, sprinkler systems, and easy escape routes
- recycled with demolition
seasoning
seasoning means when the wood is dried in order to reduce shrinking in the field
grading lumber
2 types
- appearance - what is visible to the eye. visual test
- structural - visual and machine test
wood chemical treatment
- fire-retardant treatment - elongates time before catching on fire - combustibility
- preservative-treated - decay and insects
exterior wood products
- decay-resistant and moisture resistant wood planks
- fasterners much be hot-dip glavanized or stainless steel to avoid corrosion
- always have open spaces joints to allow for drainage of water and expansion
wood fasteners
face nails - very strong
end nail - weakest fastener
toe nail - weak
fire-resistive heavy timber construction
firecut beam so that when building catching on fire the whole thing doesn’t all fall at the same time, rather it is separate
-key in preserving old buildings
difference between platform and balloon frames
plateform - new - continuous height studs - firestop - studs rest at each floor
balloon - old - by level studs - no fire stop - joists rest on ribbon
walls - framing systems
- walls are frmaed with reptitive verticcal studs that are connected at the top and bottom by horizontal platese
floors - framing systems
-floors are framed with repetitive joists that are connected at their ends by headers
roofs - framing systems
-roofs are framed with rafters. every surface is sheathed with wood panels
sitecast concrete or concrete block masonry
-typical details for a sitecast concrete foundation and basement for platform frames buildings
firewall
firewall consists of light-guage mental framing, noncombustible insulation, and gypsum board
-common in commercial
roofing underlayment
- aka building felt
- cellulose fibers with asphalt
wall moisture barrier
-repel water and restrict the leakage of air (vapour retarder is placed on the warm side of thermal insulation
ventilated roofs
-ice fams form because no insultation and no ventilation
optimizing snow melting; insulation, attic ventilation, vent spacers, and ice barrier
types of vents : soffit, gable, and ridge
climates like Canada
unventilated roof
simplicity of detailing
no risk of windblown water entry
arixona climate
drainage
- no fascia or gutter works best for steep roof with a sufficient overhand to drain water
- rule of thumb : wall is twice as tall as the depth of the overhang
- short downsprout problems : to close to foundation wall and cause soil erosion
board siding
nailed over wall sheathing and house wrap
vertical wood spacers called furring strips
shingle siding
sheathing must allow for drip
closing the open vertical jonts with the wall
each course covers the open joints in the course below
masonry veneer - siding
brick or stone
metal ties prevent masonry from falling
weep holes allow for drainage of accumulated water in cavity
insultating the buuilding frame - 6 types
High R-value = good insulation
low R-vlaue =bad insultation
- batt or blanket - rock wool: low cost, fairly high r-value, easy to install
- high-density batt - glass wool, low in cost, fairly high r-value, easy to install
- loose-fill - rock wool, good for retrofit insulation in an older building
- loose fibers with a binder- glass wool: low in cost, fairly high r value
- foamed in place - polyurethane: high r-value, high cost, seal against air leakage, vapor impermeable
- rigid board - high r-value, vapor permeable, moderate cost
thermal bridging
occurs where solid framing members interrupt the thermal insulation layer, creating wall areas with lower thermal resistance than surrounding areas, reducing the insulation efficiency of the wall as a whole
thermal bridging = one big piece of wood
thermal bridging alternative - 2 types
- insulated space between header and members of a window
2. spacer provides full nailing around the opening
