Wood Frame Carpentry

shrubflattenUrban and Civil

Nov 25, 2013 (3 years and 6 months ago)

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Wood Frame Carpentry

Floor Framing

Posts

Posts


often used in basements under main girder.


Also used in garages to support ceiling girders.


Generally spaced 8’ to 10’ on center.


Wood posts must be solid 4x4 or larger


Loads carried to fairly small area of foundation


Slab under post
made thicker to provide extra bearing capacity


Wood posts often supported by heavy gauge metal bracket to lift
clear of moisture that causes rot.


Steel posts called Lally Columns often preferred in residential.


Strong, easy to handle & take less space than wood


Must be at least 3” in diameter & protected against rust


Have steel bearing plates at each end.


Some adjustable to various lengths


Sometimes filled with concrete for extra strength

Girders

Girder


generally placed halfway between
longest foundation walls and parallel to them.


May be made of wood or steel


Steel does not shrink like wood.


Wood is lighter and easier to install. Connections easier
to make.


Floor joists usually rest on top of girder


Top of girder must be at same level as top of sill plate


If more clearance is needed girder can be installed level
with top of floor joists. Metal framing connectors attached
to girder to support ends of joists.


Girders continued

Wood Girders


available in solid or built
-
up (3
-
4
boards face nailed) wood.


Built
-
Up Girder


Stagger nails 32” on center at top & bottom


Nail 2 to 3 times at end of every board


Stagger the joints


Glue
-
laminated beams and laminated veneer
lumber may also be used





Girders continued

Steel Girders


great strength & can
span long distances


Wood bearing plate secured to top of
girder to toenail floor joists to beam


Plates can be attached with steel pins
driven with powder
-
actuated fastening tool


May be easier to attach bearing plate
before installed

Installing Posts and Girders

Installed after foundation walls are
complete & forms stripped. Basement
floor may also be in place.

Posts only located where slab is thicker
to distribute loads

Wood girders should bear at least 4” on
masonry walls to reduce risk of crushing
wood fibers

Check Your Knowledge

What is a girder, and what supports it?

What is a Lally Column?

How is a built
-
up girder constructed?

What must be done to a steel beam
before it is ready to use as a girder to
support joists and why?

Floor Framing with Joists

May use solid lumber or LVL.

Box sill


used for framing floors in
platform construction


Consists of sill plate, floor joists, rim joist &
subflooring.


Subflooring


consists of engineered wood
sheets or construction grade lumber.





Installing the Sill Plate

Sill plate


lowest member of wood frame


supports the rest.


Rests on foundation wall


Anchored with
minimum two ½” bolts per plate.


Made of 2x4 or 2x6 preservative
-
treated lumber


Set on top of foam or fiberglass
sill sealer
(comes in 6” wide rolls) fills any gaps between
foundation & sill plate.


Provides smooth bearing surface for floor joists


Connection between foundation wall & floor
system


Joists toenailed to plate or secured with
metal anchors


Installing Floor Joists

Placed perpendicular to girders 16”
-
24”
on center

Plans specify size & lumber grade

Often nailed into place. May use metal
framing connectors (joist hangers)

Spaced evenly from one end of house
to other.

Special Methods for I
-
Joists

Supported by metal joists hangers. Width of
hanger should match width of joist.

Backing block nailed to both sides of I
-
joist
improves fit.

Web stiffeners nailed to both sides of web
over supports (girders, etc).

OSB or LVL rim joist used to tie ends of I
-
joists together. Toenailed to sill plate with 8d
common or box nails spaced 6” on center.

Cutting and Notching Floor Joists

Ducts, plumbing pipes, wiring may require
notching or drilling of solid
-
wood floor joists

Careless notching or drilling can reduce
strength of joist.

Never notch in middle 1/3 of span or on
bottom edge.

Codes also restrict size & position of holes.

I
-
joist flanges must never be cut, notched, or
drilled except for cutting to length.

Bridging

Method of bracing between joists.

Done to distribute loads, prevents joists from
twisting, & add stability & stiffness

Not generally required by code unless joists exceed
2x12

Many builders add anyway. Cost effective & efficient
way to stiffen floor.

Two kinds of bridging:


Solid bridging


similar to blocking


Cross bridging


more common, very effective & requires
less material


May be wood or metal strap

Framing under Bearing Walls

Bearing wall


wall that supports loads
in addition to its own weight.

Joists doubled under load bearing walls
parallel to joists.

Double joist hanger or two joist hangers
could be used.


Framing Large Openings

Openings for stairwells & chimneys. Joists
surrounding should be doubled.

Parallel openings easier to frame than
perpendicular.

Interrupted joists supported by headers


Header


horizontal member that carries loads
from other members & directs them around an
opening.

Headers supported by trimmer joists.


Trimmer joists


used to form sides of large
opening.



Cantilevered Floor Framing

Cantilever


supporting member that projects
into space and is supported only at one end.

Floor joists that extend beyond foundation
wall.

Joists carry necessary loads. Cantilevered
extensions should not exceed 2’.

Joists forming each side and header should
be doubled.

May require preservative
-
treated lumber.


Bathroom Floor Framing

Weight & drainage requirements of plumbing
fixtures involve special framing

Joists supporting tub & shower should not be
cut or notched to connect drainpipe.

Joists parallel to length of tub should be
doubled under outer edge.

Unusually large tubs require extra support.

Second Story Framing

Basically same as for first floor.

Joists rest on double top plate of first
-
story walls.

Finish ceiling materials will be nailed to
underside of joists. Must have nailing
surface (doubled joists) along edge to
attach ceiling materials.

Check Your Knowledge

What is the purpose of the sill plate?

What is a web stiffener and what is its
purpose?

The Subfloor

Lends bracing strength to building.

Provides solid base for finish floor.

Helps keep building warmer & drier in
winter.

Provides a safe working surface for
building house.


Fastening the Subfloor

Common nails often used to install floor
sheathing.

Some manufacturers recommend ring
-
shank or screw
-
shank nails. Better
holding power.

Even better connection & fewer
squeaks. Use screws.

Nailing Techniques

Pneumatic nailing


standard method

Self
-
feeding screw guns used to speed
installation of screws

Glue
-
nailing


bead of adhesive applied to
tops of joists before panels are nailed in
place. Results in stiffer floor, less likely to
squeak.


Adhesive should be applied immediately before
each sheet of subfloor is installed to prevent
adhesive from drying too much.

Blocking

Edges of square
-
edged sheathing
panels should be supported.

Must rest on joist or blocking laid
between joists.

Tongue
-
and
-
groove sheathing does not
require blocking

Single
-
layer Floor Systems

Designed for use under wall
-
to
-
wall
carpeting & carpet pad.

Fastened directly to joists


has only
one structural layer.

Panels used for single
-
layer should be
rated for this purpose.


Double
-
layer Floor Systems

Separate subfloor & underlayment

Used under finish floors like sheet vinyl

Subfloor attached to joists.
Underlayment goes on top & covers any
minor construction damage.


Check Your Knowledge

When glue
-
nailing a subfloor when
should adhesive be applied to joists?

List four fasteners used to attach
sheathing to floor joists.

What is underlayment and why is it
used?


Other Floor Framing Systems

Floor Trusses


may be used in place of floor
joists where must span long distances.


Made in factory to job specifications


Allow heating ducts, water & drain lines to pass
through easily.


Most common type in residential is parallel
-
chord
floor truss. Top & bottom chords parallel to each
other over length of truss


Three basic parts:


Chords


Webs


Connector plates

Other Floor Framing Systems
continued

Girder Floor Framing


system of posts
& girders support subfloor instead of
joists.

Sometimes used over crawlspaces.


4x6 girders used & spaced 4’ on center.

Check Your Knowledge

Name the three basic parts of a floor
truss.

Name one advantage of floor trusses.

Where is girder floor framing used?