Glencoe: Section 62 Flashcards
Because qualities of each LVL can be controlled
LVL products are very predictable. Most pieces will behave like other pieces in the load.
Which is stronger: LVL or Solid Lumber
LVL
Laminated Veneer products should be handled in the following way:
Do not store on ground or needlessly subject it to moisture. Do not remove wrapping until ready to install.
One of the most common Laminated veneer lumber products is
I-joist
Joist:
type of beam used to support a floor, ceiling, or roof.
Anatomy of an I-joist
vertical member is called a web
horizontal is called flanges.
I-joists are most often used:
floor construction to support subflooring, and used in place of rafters in roof construction
Top and bottom flanges of I-joists can be
made of solid lumber or laminated veneer lumber
I-joist flanges range from X in width
1 1/2’ to 3 1/2’
Web of I-joist may be made from section of X plywood or OSB.
3/8”
LVL I-Joists are commonly available in depths of X inches
9 1/2”, 11 7/8”, 14”, and 16”
Most common spacing of LVL I-Joists
16 on center
I-joists advantages over solid lumber joists
available in long lengths that can span entire house. Flooring can be installed faster. I joist is lighter.
Span table:
list of distances that a particular structural product can span between structural supports such as walls or columns.
Easiest method of cutting an I-joist
use a radial arm saw or a large slide type miter saw and placing a wood block against flanges and web to prevent shoe of saw from lodging
Where does permanent bracing for I-joists come from
sheathing, rim board, cross bracing
If temporary bracing for I-joists is required, do the following.
- Use stock at least X in size
- Braces should at least X long. Space no more than X on center.
- Secure each brace into the top of each I-joist using two X nails
- Nail the bracing to a lateral restraint, such as X or X
- Lap the ends of adjoining bracing over at least X I-joists.
1' x 4' 8' 8' 8-d an existing sub floor or braced end wall at the end of each bay. two
I-joist used in floor construction are installed in a way similar to solid lumber joists. They can be nailed to the plate by toe X. They can be braced with Y
nailing through the lower flange or secured by metal joist hangers
solid blocking, I-joist blocking, or metal cross-bracing.
Joist hangers are generally nailed to the I-joist with X common nails
10-d
Never drive nails into an I-joist X
sideways because it splits the layers, always do a 45 degree angle into the flange.
Web stiffeners, bearing blocks, or squash blocks
thin strips of wood installed against both sides of the web to reinforce the web and prevent it from buckling at points of high stress.
Bearing stiffener:
where a web stiffener is installed where the i-joist crosses mid-span support.
Load stiffener:
a web stiffener is installed where a load is expected from above.
Stiffeners should be at least
2 15/16” wide.
A flange 1 1/2” wide calls for stiffeners at least X thick
15/16”
A flange 2 15/16” wide calls for stiffeners at least X thick
1”
A flange 3 1/2” wide calls for stiffeners at least X thick
1 1/2”
The web of a wood I-joist often has pre-scored knockout holes about X on center along its entire length
12”
What if you want to knock out more holes from an I-joists web?
Follow the manufacturers instructions
Rim Joist
when a floor is framed with conventional lumber, the ends of the floor joists are connected with solid lumber of the same size called Rim Joists
Solid lumber Rim Joists should not be used
with I-joists because the two products expand and shrink differently
What Rim product should be used with an I-joist
Rim Board
Standard Rim Board thickness
1” to 1 1/2”
Store I-joists on X because Y
Store I-joists on edge because they are weak in lateral strength.
What is the danger of storing or carrying I-Joists on their sides
glued butt joints could break,
Two people should carry long I-Joists
Never notch or drill into the X of an I-Joist. This could weaken the product.
top or bottom flanges
If bundles of I-joists are stacked, X
Separate them with stickers
Instead of carrying a standard grade stamp, I-joists are stamped to identify X
a specific performance standard it meets
Performance standard:
a standard that defines the required behavior of a specified building componant.
I-Joist performance stamps are located
on the flanges.
Laminated Veneer lumber can be used like
solid lumber for many purposes
What is laminated veneer lumber most often used to replace?
solid-wood or built-up-wood headers and beams
LVL header and beam stock comes in various thicknesses. Most common:
1 3/4” thick.
When two 1 3/4” thick LVL header and beam stock are combined, they form:
equal thickness of a standard 2x4 wall.
LVL headers and beams commonly range in depth from
5 1/2” to 18”
When nailing LVL headers face to face, use X rows of Y nails spaced Z on center.
3
16d
12”
Holes should not be cut in LVL headers or beams without
consulting manufacturers recommendations
What type of tool should be used to cut LVL headers on site
Carbide-tipped blades
When layers of lumber are glued together, their strength and stiffness are X than Y
greater than that of solid lumber of equal dimension
Glulam
Stronger than a steel beam. Multiple layers of lumber glued together.
What are glulams commonly used for?
garage door headers, patio-door-headers, carrying beams, window headers, exposed stair stringers.
How do glulams fare with fire
very fire resistant and do not ignite easily. Glulams retain much of their strength in fires.
Manufacturing Glulam:
Glulam is made by gluing lengths of dimension lumber together and curing at room temp.
Grain of all layers parallel.
Most common woods in Glulam
Southern yellow pine and Douglas Fir
Glulam layer thickness
Each layer is no more than 1 1/2” thick.
The best quality layers of glulam are placed where?
Top and bottom. This increases its trength by 100%.
When a one-hour fire rating is needed for glulam
addition layers are placed at bottom of beam
Camber
Glulam camber is when glulam is manufactured with slight upward curve. When the beam is fully loaded it straightens out.
Glulam camber is measured in two ways
Inches of camber. The amount the beam curves above the flat surface.
Radius of curvature. The camber represents a segment of a huge circle.
Stock glulam beam radius:
3,500’ in residential
1,600’ to 2,000’ in commercial
How many glulam grades are there
4 none differ in strength, only appearance. Framing grade Industrial grade Architectural grade Premium grade
Why is it becoming difficult to find lumber of consistent quality?
Heavy demand for wood products and decreasing forest resources.
Finger jointed lumber (structural end-jointed lumber)
Lengths of lumber are joined end to end by closely spaced series of wedge shaped cuts made in the mating surfaces of lumber. Glue bonding is placed here.
Advantages of finger-jointed lumber
always straight
can be sawed and nailed exactly like solid lumber
makes use of short pieces otherwise wasted
available in longer lengths than standard lumber
Building codes treat lumber with certified exterior joints as
if it were standard lumber, so it can be used interchangably
The grading agencies which supervise the manufacturing of standard lumber also supervise
finger-jointed lumber.
What do the grading stamp on finger-jointed lumber indicate
grade of wood, species, type of glue.
Finger-jointed lumber with Certified Exterior Joint grade:
uses exterior grade adhesives and has fingers that are 7/8” to 1 1/8” long
Finger-jointed lumber with Certified Glued Joint grade:
are suited for vertical use only. (sometimes stamped stud use only or vertical use only)
It does not use exterior-grade adhesives and the fingers are 3/8” to 5/8” long. Store indoors away from water
Finger jointed studs are manufactured in sizes of
2x2, 2x3, and 2x4 (most common), 3x4 and 2x6
they may be up to 12’ long
Laminated-Strand Lumber is
made of wood strands glued together and cut to uniform dimensions. Predicable performance
LSL manufacturing process
After debarking logs are made into wood strands 0.03” to 0.05” thick, 1” wide and 12” long.
Strands are sorted then covered in wax and adhesive. Formed into mat. Mat is cut to 35’ to 48’ then pressure and heated.
Billet
Long block of manufactured wood that will be cut into smaller pieces.
After an LSL has cooled, the billet will be cut into lengths up to
22’ then graded
PSL (parallel strand lumber)
Logs are cut to 8’, rotary peeled into veneer with thickness of 1/10” or 1/8”. Veneer is cut into large ribbons 1” wide by 8’ long. Covered with adhesive and wax. The mat is then compressed and cured using Microwave energy.
What is glulam short for?
glue laminated beam
After the PSL has been microwaved, how thick may the resulting billet be?
up to 11” thick.
OSL
oriented strand lumber relatively new. It is similar to Oriented Strand board except that the strands are aligned along the length of the product. It is also similar to laminated strand lumber except that the strands are shorter.
Where is OSL used?
core of entry doors, frame of window, upholstered furniture.
Laminated strand lumber is made from
fast-growing aspen or yellow poplar
Parallel strand lumber is made from
Douglas fir, western hemlock, southern pine, yellow poplar logs
Pros of wood frame houses
Cost less than other systems
easily insulated
can support wide variety of exteriors
durable
Main pieces of conventionally framed wood house
Joists, studs, beams, and rafters. Spaced at regular intervals supporting the house.
Sheathing:
wood panels fastened to the wood framing to give it more stiffness.
Two components which form the basic structure of house
framing and sheathing
Two main type of conventional framing
balloon-frame and platform-frame.
Balloon-frame construction
(balloon framing) the studs run from the sill plate to the top plate of the second floor. The first floor joists also rest on this sill. Wall studs extend continuous lengths from one story to another. All joints are nailed.
In balloon-frame construction the second floor joists
bear on 1x4 ribbons (ribands) cut into the inside edges of the studs.
Why is balloon-frame construction less affected by expansion?
Because less cross-grain framing is used.
Is balloon frame construction used in modern houses?
no. Because long straight lengths of lumber are no longer readily available. Finger-jointed makes this type of construction viable.
Platform-frame construction
(platform framing) each level of the house is constructed separately. The floor is a platform built independently of the walls.
In Platform-frame construction, the top surface of the platform is called
the subfloor. It extends to the outside edges of building.
In Platform-frame construction, each wall is usually
assembled flat on top of a subloor then tilted into place.
General sequence of constructing a multi-story building with platform framing:
- installation of a foundation.
- The first level floor joists are installed and sheathed.
- The first level exterior and interior walls follow. Exterior should be sheathed before second level is built to give rigidity.
- Second floor joists installed and sheathed. coiling joists and rafters installed and roof sheathed.
Because Platform-frame construction is prone to failure as each piece is separate, how do builders protect the home against seismic activity and wind?
metal framing connectors.
Advantages of Platform-frame construction
lends itself well to prefab. Walls can be prebuilt then lifted into positon.
Does not require unusually long lengths of lumber.
In balloon frame construction, let in brace:
Let-in brace 1” x 4” diagonal going through the studs
In standard platform-frame construction, wall studs are commonly spaced
16” apart on center.
however floor joists may be spaced at intervals of 12”, 16”, 19.2”, or 24” OC.
Because in platform-frame construction wall studs can be spaced intervals of 12”, 16”, 19.2”, or 24” OC, structural loads are not always passed directly from one framing member to another, this is not a problem because:
wall plates distribute the loads. and the number of studs make up for irregularities.
In-line framing
all joists, studs, and rafters are given the same spacing (usually 16”, or 24” OC). Creates a direct path for loads right down to foundation wall. Double top plates are note required because of load bearing-effeciency.
Advanced framing (Optimum Value Engineering)
comprehensive system designed to reduce the amount of lumber needed to build a house. Houses are planned in 2’ modules and includes details such as 2 stud corners.
Post-and-beam framing
framing system that relies on fewer but larger pieces of framing members are spaced further apart than conventional framing.
In Post-and-beam framing subfloors and roofs are supported by a series of beams spaced
8’ apart.
In Post-and-beam framing, the ends of beams are supported by structural timer posts that is
5x5 or larger.
In Post-and-beam framing, the roof sheathing and subloor may consist of planks, usually with a X nominal thickness or structural tongue-and-groove plywood that is Y thick.
2”
1 1/8”
Advantage to Post-and-beam framing
the architectural effect provided by the exposed framing in the ceiling. Thick roof planking serves as the finished ceiling as well as the structural support for the roofing.
A varation of Post-and-beam framing in the pacific northwest and areas of mild weather is:
First floor is framed using post and beam, the rest is platofrm framing. Cost effecient when building a house with crawl space foundation.
Timber-frame
type of post and beam that rests on a foundation. Supporting members are fairly far apart. Timbers are surfaced then connected with interlocking joinery (morise and tenon) secured with square pegs.
