Structural/Rough Carpentry

Question 1

Structural/rough carpentry includes

Answer 1

structural framing, sheathing, blocking, anything to prep for finish work

Question 2

Wood/lumber/timber

Answer 2

wood = comes from trees lumber = product of sawing, planing, etc. timber = at least 5 in. min. section

Question 3

Adv./Disadv. of lumber

Answer 3

good: low cost, low footprint, easy to work, good insulator
bad: non-uniform, low strength, susceptible to moisture

Question 4

Softwood vs. hardwood

Answer 4

soft: conifers (used for rough)
hard: deciduous (used for finish)

Question 5

Lumber strength

Answer 5

depends on grain direction relative to load; best when load and grain parallel (eg., load on wood column); worst in bending

Question 6

Lumber defects

Answer 6

knots (branch/limb), checks (growth rings are separated, pulled apart), pitch pocket (same as check, but filled w resin), shake (like check, but lengthwise instead of across grain), split (like check, but goes through piece of lumber, often at ends), wane (where bark was, or where chunk is just gone, usu. at corners)

warping: out of plane; bow warp - parallel, crook warp - side to side, cup = along width

Question 7

Lumber grades

Answer 7

made by American Lumber Standards Committee; yard lumber: for structural/rough; factory/shop lumber: for finishing

Question 8

Yard lumber

Answer 8

boards (less than 2), dimension (2 to 5), timber (more than 5)

2x2s, 2x4s (subdivided), 2x6s+

beams/stringers: 5” wide, 2”+ depth

posts/timbers: 5x5, depth not more than 2” than width

Question 9

Factory lumber

Answer 9

grade B/better (best), C/select, D/select

common grades: no.1-no.5 (1 = best, usu. based on knots)

Question 10

Nominal/Actual dimensions

Answer 10

1”=.75”

2-6=2.5-6.5

8-12=7.25-11.25

Question 11

Moisture content

Answer 11

expressed as fraction of the overall weight of oven-dried wood; 30% = fiber saturation = when no water in cell cavities, but cell walls saturated = pt. when shrinkage starts to occur

Question 12

Wood seasoning

Answer 12

Putting lumber on site, so it has time to shrink/swell to local/prevailing moisture content levels

Question 13

Dry lumber

Answer 13

moisture content below 19% (req’d for structural lumber design values)

kiln dry = below 15%

Question 14

Wood shrinking/swelling

Answer 14

occurs most perpendicular to grain, very little parallel to grain, most tangentially to growth rings, half as much radially

Question 15

Wood stud construction

Answer 15

aka light frame wood construction, 2x4s or 2x6s, with a few heavier beams of built-up/heavy timber/steel members; can be platform (easier to construct) or balloon framing (less vertical shrinkage, stays parallel to wood grain)

Question 16

Wood to masonry wall

Answer 16

hung by wood ledger + metal joist hanger or use fire cut (to prevent masonry from being pushed up/out when beam burns out)

Question 17

Plywood ratings

Answer 17

thin wood veneer sheets glued together, usu. 4’x8’, in .25”-.75” thickness, graded by span (measures stiffness/strength of parallel to face grain - eg 32/24, max dist. roof supports/max dist. floor supports, average residential conditions), also graded by wood species (I = group I woods, II = woods 2, 3, 4), graded by quality of face veneer (N natural finish, heartwood/sapwood, free of defects, A, B plugged knotholes, C small knothole/splits, D large knotholes); can have special glues/finishes for tough environments

Question 18

Types of plywood

Answer 18

sheathing = attached to framing to provide structural support

particleboard = small wood particle/fibers/chips (low/med/high density), mostly for backing

OSB = oriented strand board - precision cut wood strands of 4” length, .0027” thick, layered at right angles, comes in bigger panels, subject to delamn.

MDF = medium density fiberboard - fibers made by steaming wood, most dimensionally stable panels, smooth face for finishing

hardboard = inter-felted fibers, can be tempered for hardness

Question 19

Blocking, bridging

Answer 19

blocking = pcs btwn framing for rigidity or nail base

bridging = bracing btwn joists to prevent joist buckling (can be wd blocking or metal cross braces), usu 8’ + o.c.

firestops = barriers in concealed framing spaces, can be 2”+ wood, gypsum, mineral wool

Question 20

Engineered wood

Answer 20

smaller/waste woods to make stonger, bigger members; glue/metal fasteners/insulation used; includes plywood web joists (TJIs) (less wasteful, stronger, less shrinkage), laminated veneer lumber/structural composite lumber (thin lams parallel to length), trusses, SIPs panels, composite decking, CLTs cross-laminated timbers, glulams

Question 22

Wood truss types

Answer 22

king post, queen post, Fink, scissor, Warren, Howe Pratt

Question 23

SIPs

Answer 23

structural insulated panels: usu. OSB + EPS (expanded polystyrene)

other facings: plywood, Al panels, cement board, gypsum wallboard

other insulation: extruded polystyrene (XPS), urethane foam, compressed straw

thicknesses btwn 4.5”-12.25”, usu. 4’x8’ to 9’x28’

reduce construction time, improved insulation values bc reduced air infiltration, higher strength, flatter surfaces, dimensional stability

problems w/seismic anchoring, vapor barrier placement, insect damage

Question 24

Composite wood decking

Answer 24

wood-plastic composite - planks formed from ~50% sm. wood fibers or wood flour mixed w ~50% plastic (polyethylene), along w/ colorants, stabilizers, fungicides

lasts longer than dimensioned lumber, stronger, splinter-free, recycled materials

hotter underfoot, warp prone

Question 25

Cross-laminated timber

Answer 25

CLT, layer dimensioned lumber at right angles to make panel, very strong, resist bending, racking, act as strong diaphragm, can use smaller diameter trees since acting togther (green)

Question 26

Heavy timber construction

Answer 26

Main framing members of bldg from large dimensioned wood or engineered wood

Question 27

Glulams

Answer 27

Glue-laminated wood members; depths are multiples of 1.5” (2xs), higher allowable stresses bc members defect free, dried, etc.; specified by stress rating; grades are industrial (rough), architectural (medium), premium (finest)

Question 28

Wood decking

Answer 28

aka planking, solid or lam timber spanning btwn beams, usu. TNG, spans more than sheathing (4’-20’), can be both structural & finish floor/ceiling (but hard to conceal insul, services

= heavy tiber constr.!

Question 29

Wood fasteners

Answer 29

nails (weakest, most common - box, common wire, wire spikes), screws (flat/round head, threading makes stronger cnxn, lead holes make stronger, lag = pointed end but head like bolt), bolts (use washer at head to distribute load), metal fasteners (lightweight connectors, timber conn., split rings, shear plates to transfer loads, gang nail plates), etc.

use nailing schedule for size, number, spacing, penetration type

Question 30

Wood treatments

Answer 30

preservatives brushed, dipped or pressure applied to fight moisture + insects

creosote (coal tar, water proof, RR ties, marine structr.), oil-borne (penta/pentachlorophenol, for utility poles, pilings, bridges, long spans over swimming pools), water-borne (ACQ/ammoniacal copper quaternary, sodium borate/SBX, etc., lesser VOCs, paintable, but don’t use w Al bc corrosive); treat all cuts w 2% copper in copper naphthenate

no longer used: CCA/chromated copper arsenate, ACZA/ammoniacal copper zinc arsenate bc of arsenic content, but were less corrosive