Hard Materials

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Hard Materials

• Topic 2217
• By Kathryn Wagar

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Hard Materials

• Working with outdoor lumber
• Building Tips
• Designing and Building Stairs

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Working with outdoor lumber

• What you should know
• How Pressure-treatments work
• Types of Outdoor lumber
• Pentachlorophenol-treated lumber
• Chromated Copper Arsenate-treated lumber

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Things you should know about pressure treated
lumber

• In any outdoor project the wood suffers from
  constant exposure to the elements
• To prolong the life of the project, you will want
  to use types of wood that weather well
• Unprocessed woods Redwood, cedar, cypress
• Pressure-treated lumber or outdoor lumber

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What you should know Cont.

• Natural decay-resistant woods have become quite
  expensive
• A sunshade gazebo made from redwood will cost you
  two to four times what it would cost to build the
  same project from ordinary spruce and fir.

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Inexpensive Alternative

• Outdoor Lumber
• This is ordinary spruce and fir lumber that has
  been cooked at high pressures in chemical
  preservatives so that the chemicals penetrate
  deep into the wood
• This treatment makes the lumber every bit as
  decay-resistant as the natural alternatives

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Cons to using Outdoor Lumber

• It also makes the lumber potentially harmful, if
  not handled correctly
• The chemicals used to treat outdoor lumber can be
  poisonous to plants, pets, and people
• If youre going to work with outdoor lumber, it
  behooves you to know something about it, and its
  dangers, so that you can avoid any problems.

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How Pressure-Treatments Work

• Why Wood deteriorates
• Why Chemicals are used
• Importance of technique

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Why Wood Deteriorates

• Two reasons
• Fungal decay or insect attack
• Requires that certain conditions exist before it
  can proceed
• Both fungus and insects require sufficient
  oxygen, moisture, and food to do their work
• The wood itself serves as the food, oxygen is
  always present in the air surrounding the wood,
  and the outdoors gets awfully wet from time to
  time

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Why Chemicals are Used

• The chemicals used to treat outdoor lumber
  prevent fungal decay and insect damage by
  poisoning the food source
• As a result, treated lumber can maintain its
  integrity for many years
• Estimates of the life of pressure-treated wood
  range from 40 up to 100 years, depending on the
  chemical, the wood type, and how the wood is used.

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Importance of Poisoning Technique

• When you poison a board, its important to poison
  the entire board, inside and out.
• This is why the lumber is pressure-treated
• You can paint, stain, or even soak ordinary
  lumber in the same chemicals, but not get the
  same results
• The protection will only extend a short distance
  into the surface of the wood

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Importance of Poisoning Technique

• Prior to the widespread availability of
  pressure-treated lumber, some companies would
  incise the lumber before treating it, in an
  attempt to make the wood more decay-resistant.
• They ran the stock between sharp toothed rollers
  to separate the wood fibers and allow the
  preservative to penetrate more deeply
• But these incisions still did not allow the
  preservative to soak in much beyond the depth of
  the cuts.

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Commercial Pressure-Treating

• Distributes the preservative throughout the wood
• Treating mills typically dry the wood to about
  20 moisture content, then stack the lumber in a
  huge retort.
• After sealing the retort, they pump all the air
  out, creating a vacuum and extracting most of the
  remaining moisture

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Commercial Pressure Treating Cont.

• Once the moisture falls to the desired level, the
  retort is flooded with preservative and
  pressurized to at least 175 pounds per inch
• This pressure is kept up for hours, drying the
  preservative into every wood cell

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Commercial Pressure Treating Cont.

• After a prescribed time, the retort is drained
  and all the air pumped out, creating a second
  vacuum to remove any excess preservative or
  moisture
• The wood is removed from the retort and stacked
  in the open air to complete the drying process

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Any Questions?
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Types of Outdoor Lumber

• There are three types of pressure-treated lumber
  widely available today, and these are classified
  according to the chemicals they have been treated
  with
• Creosote
• Pentachlorophenol
• Chromated Copper Arsenate (CCA) (Most common)

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Creosote-treated Lumber

• Oldest of wood preservations
• Oily or dry
• Harmful to pets and humans
• Minimizing dangers

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Creosote

• A coal tar distillate
• Oldest of the wood preservations used today
• Most commonly used in utility poles, railroad
  tiles, and landscape timbers
• Applied under pressure with considerable heat to
  make the solution thin enough to fully penetrate
  the wood

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Creosote

• Lumber can be oily or dry, depending on the
  degree of treatment, and if they all emit a
  strong odor
• Paint will not bond to creosote surfaces
• Creosote doesnt fix chemically to wood
• Preservation will Leech out

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Leeching of Creosote

• Occurs in warm weather
• Makes the wood harmful to plants
• Newly creosoted timbers should not be used for
  gardens
• Old railroad tiles that have lost most of the
  preservation may be used
• Once preservation leeches out, wood may decay

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Creosote can be harmful to Pets and People

• Sticky residue that accumulates on your hands and
  arms as you work with the treated lumber can
  cause skin irritation
• The fumes are poisonous

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Dangers that can be minimized

• Dangers can be minimized by sealing the wood with
  urethane, epoxy, or shellac
• helps prevent leeching
• Adds or work and money
• Dont use where it will come in contact with pets
  and humans

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Examples

• Good uses for Creosote lumber
• piers
• bridges
• poles
• ties,
• landscape timbers

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Questions?
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Pentachlorophenol-treated lumber

• Definition EPA-registered pesticide containing
  chemical Pentachlorophenol applied to lumber
• commonly called penta

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Penta Lumber

• Can be either water or oil soluble
• both are toxic
• Neither bond permanently to wood
• Has similar problems as creosoted lumber
• Only advantage over creosote is that its not as
  messy to work with and it can be painted on
  after being set out in weather for some time

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Penta Lumber

• Dangerous to use in areas that it may come in
  contact with people (particularly bare skin),
  animals, and food do to toxicity and leeching
  problems
• Best suited for remote structures where it will
  pose no serious threat
• Todays utility poles are generally treated with
  penta

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Questions?
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Chromated Copper Arsenate-Treated Lumber

• Facts
• Dangers/advantages
• Uses for Different strengths
• uses

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Facts of CCA

• Newest development in pressure-treated lumber
• This is another EPA-registered pesticide,
  containing inorganic arsenic
• Water soluble
• No fumes, can be used in interiors
• Bonds permanently with wood
• Can be painted
• Best choice for homeowner outdoor projects

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Dangers/Advantages

• Even though CCA itself is toxic, when its bonded
  to wood, its relatively harmless
• Little residue do to not leeching
• Still recommended to let it weather before
  children and pets go near structures
• Once structure is washed its relatively
  harmless
• Should never be used in areas that it may come in
  contact with food and water

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Uses for Different Strengths

• Treatment plants use CCA solutions of different
  strengths, depending on the intended use of the
  lumber
• most common strength is .40 lb/ft3 of wood after
  pressure treating (referred to as the retention
  figure)
• This provides an acceptable balance between the
  expected life of the wood and the cost of the
  chemical treatment

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Uses

• Fence posts, small structural timbers (4X4s),
  landscape timbers -- wood that will come in
  direct contact with the ground -- is generally
  rated at .40 pounds
• most building supply stores will only carry .40
  pounds
• Decking and timbers that dont touch the ground
  may not need that high of rating

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Uses

• If you get lower rated stock, you can save some
  money
• If youre using larger timbers than 4 X 4s as
  structural members, you may need to put out the
  extra expense for a higher rating
• Consult the notes to be sure of exactly what you
  need

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Big Advantages

• One of the big advantages of CCA-treated lumber
  is that it can be painted
• Air-dry for two to six months before you paint
  unless it is kiln-dried (unusual)
• Helps to make sure all water has evaporated and
  the paint will bond properly

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Big Advantages

• Additional note
• When CCA first appeared, the chemical solutions
  contained impurities such as sulfate and sodium
• These are called salt solutions, and they would
  precipitate out of the wood to form a whitish or
  greenish-gray residue on the surface
• This residue contained high levels of arsenic and
  would quickly corrode nails and fasteners

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Big Advantages

• Today, most manufacturers use a different type of
  CCA solution, called an oxide solution
• This produces clean, dry, well-preserved lumber,
  relatively fee of any arsenic-tainted residue
• You should not have any problem with lumber
  treated with this type of CCA

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Other Warnings

• Even though pressure-treated lumber is relatively
  safe if used properly, it does contain
  potentially dangerous chemicals
• Because of this, you should handle outdoor lumber
  with respect and take certain precautions when
  working with it
• Probably the most important precaution is to
  never burn the scraps in the open, in a
  fireplace, or in a stove

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Other Warnings Cont.

• All types of outdoor lumber -- creosote, penta,
  and CCA -- produce poisonous gases when burned
• When youre done working, carefully clean up all
  the scraps and sawdust
• Dispose of these in a local landfill, or bury
  them yourself

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Any Questions?
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Building Tips

• Buying wood
• buying hardware
• Prevention maintenance

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Purchasing Wood

• When purchasing pressure-treated lumber, pay
  attention to what species of wood youre buying

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Purchasing Wood

• East of the Mississippi, the predominant wood
  varieties used are Southern Yellow Pine, a good
  hard conifer wood and Red Pine Used mostly for
  fence posts and landscape timbers
• West of the Mississippi, Ponderosa Pine
  predominates

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Purchasing Wood

• All three of the listed species are well suited
  fore pressure-treating, and they have good
  structural integrity and dimensional stability
• Douglas Fir, Spruce, and White Pine, along with
  most common hardwoods, do not accept chemical
  preservations well
• Douglas Fir Will not accept chemicals even after
  incising

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Purchasing Wood

• Consequently, you should avoid purchasing these
  species
• As a rule, manufacturers will use the wood that
  is most cost effective for them to treat, and it
  just takes to much effort to get a good retention
  figure with anything other than the three we
  listed before
• So you wont often run into treated Douglas Fir
• It is still wise to look

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Buying Hardware

• When purchasing fasteners and hardware, look for
  hot dipped, galvanized or stainless steel nails,
  screws, hinges, etc.
• These will resist corrosion, and they wont stain
  your project with rust streaks
• When nailing, drive nails at a slight angle
  through the top board into the receiving board

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Buying Hardware

• Vary the angle back and forth
• This will help hook the lumber together, and
  lessen the chance of a board working loose
• You may also want to use a nail set to avoid
  making hammer marks -- smiles in the surface
  of the wood and a drill to drill pilot holes to
  prevent narrow boards from splitting

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Buying Hardware

• Nail the boards -- especially decking or flooring
  boards -- bark side up.
• You can determine the bark side by looking at the
  end of a sawn board to see which way the annual
  rings curve
• The bark side will always be above the crown of
  the rings

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Buying Hardware

• By nailing the bark side up, the bark will shed
  water better
• This, in turn, helps inhibit the boards tendency
  to cup
• And should some cupping occur, the board wont
  have raised edges that form tow-stubbers and
  heelcatchers.

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Buying Hardware

• While youre building, remember that the wood
  will still retain some moisture and will shrink
  after some months have passed
• The original green color of most treated lumber
  will not remain forever, so dont fret if you
  dislike it
• After six months of weathering, the green will
  begin to face to a pleasant silver-gray color and
  remain that way

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Buying Hardware

• Some manufactures use a CCA solution thats been
  tinted with a brown dye, to make the stock more
  visually pleasing.
• But this doesnt last either
• Even these brown boards fade to silver-gray after
  a few months out in the weather
• If you want some other color than gray, just wait
  a few months and paint or stain the wood to suit
  yourself

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Prevention Maintenance

• Using pressure-treated lumber will prevent the
  ravages of insects and decay on your carefully
  planned, laboriously constructed outdoor project

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Prevention Maintenance

• To get the best results, you need to choose the
  materials that best suit the project work with
  the materials as they are intended to be worked
  with and, above all, follow a few simple
  precautions to keep you and your environment safe
  from the possible effects of toxic chemicals.
• If properly used, outdoor lumber will poison the
  bugs and the fungi, but nothing else

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Questions??
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Designing and Building Stairs

• Basic Stair Types
• Designing a stairway
• Definitions
• Layout
• Carriage dropping
• Tread and Risers
• Stair assembly

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Basic Stair Types

• Cleated stairway
• Simplest, relies on wood or metal cleats fastened
  to the carriages to support the treads
  (ever-loosening cleats)
• Wood cleats
• Are 1X4, screwing them over nailing. Angle-iron
  cleats last longer. Used in the back porch and
  cellar

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Basic Stair Types

• Open-tread stairway
• Without risers, uses dadoes carriages.
• The treads have 1/2 inch or more bearing on the
  inside face of the carriages, and they are either
  nailed or screwed in place
• Use a circular saw, set depth of cut to half the
  thickness of carriage and make parallel cuts
• Utility stairs (porches and decks)

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Basic Stair Types

• Cut-out Carriages
• Basements
• Finished Stairway
• Patient finish work, less tedious to build with
  cut-out carriages hidden below the treads
• Treads and risers are scribe to the skirts

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Questions?
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Designing a stairway

• Comfort
• Stair width
• Headroom
• Basement 6ft 6 in
• House 6 ft 8 in

• Code
• Maximum rise of 8 1/4 in and a minimum tread
  width of 9 in
• Riser tread 17.5 (a 7-in riser a 10.5-in
  tread 17.5 in)
• Riser X Tread 75 (710.573.5)

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Designing a Stairway

• Safety
• Each tread should project over the riser below
  it. No more .25 in and no less than 1 in.
• Handrails should be between 30 in and 34 in above
  the nosing with 1.5 in clearance between the
  handrail and the wall

• Cost

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Questions?
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Definitions

• Balusters
• The posts or other vertical members that hold up
  the handrail, usually 2 per tread
• Balustrade
• The complete railing, including newel posts,
  balusters and a handrail. Most of these parts are
  available as stock finished items at lumber yards

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Definitions

• Carriages
• Also called stair stringers, stair horses or
  stair jacks. They are the diagonal members that
  support the treads. Carriages can either be
  finish stringers or rough stringers - for an
  outside stairway, or for an inside stairway
  hidden from view
• Rough carriages are cut-out carriages, dadoes, or
  cleated stairs, made of 2x10 or 2x12 softwood
  lumber
• Finish stringers are usually made of 3/4 in or
  1.5 in stock. Either cut out or routed

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Definitions

• Closed Stairway
• Stairs with walls on both sides. In this case a
  wall stringer, whether it is a housed stringer or
  just a stringboard, is nailed to each wall.
  Closed stairways use handrails, not a balustrade.
  
• Finished Stairway
• Any of several interior stair types that have
  risers, treads, stingers and a handrail or
  balustrade

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Definitions

• Handrail
• This rail runs parallel to the pitch of the
  stairs. Its held by balusters or brackets
• Headroom
• the vertical distance from the lowest point of
  the ceiling or soffit directly above the stair to
  the nosing line, an imaginary diagonal connecting
  the top outside corners or treads. Most codes
  requires at least 6 ft 8 in for stairs in living
  areas and 6 ft 6 in for basement utility stairs

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Definitions

• Housed stinger
• The profile of the treads, nosing and risers is
  routed into a finish stringer. Extra room is
  left for wedges to be driven and glued in between
  the stringer and the treads and risers. Rabbeted
  and grooved risers and treads are Also used
• Landing
• A platform separating two sets of stairs

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Definitions

• Newel post
• The large post at the end of the handrail. There
  is a starting newel at the base of the stairs,
  and a landing newel at turns.
• Nosing
• The rounded front of the tread that projects
  beyond the face of the riser 1 in to 1.25 in. In
  the case of open-tread stairways, it shouldnt
  exceed .5 in. In most cases, the nosing is milled
  on the tread stock. On open stairways, a
  half-round modeling called return nosing is
  nailed to the end of the tread

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Definitions

• Open or mitered stringer
• This is cut-out finish stringer used in open
  stairways. The treads carry over the stringer,
  but the vertical cut-outs on the carriage are
  mitered with the risers at 45 degrees.
• Open stairway
• This can be open on one or both sides, requiring
  a balustrade. In finished stairways, the open
  sides will use a mitered or open stringer

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Definitions

• Rise
• The height of each step from the surface of one
  tread to the next. Just as in roof framing, this
  measurement is sometimes called the unit rise.
  Many codes call for a maximum rise of 8.25 in.
  The height of the entire stair, from finished
  floor to finished floor, is the total rise
• Riser
• Describes the rise of one step. It is also a
  stair part-the vertical board of each step that
  is fastened to the carriages. Risers for a
  housed stringer stair are rabbeted at the top to
  fit the tread above, and grooved near the bottom
  for the tread below. Other stairs use a 1x
  square-edged stock. Open-tread stairs dont have
  risers

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Definitions

• Run
• Also called unit run, this is the horizontal
  distance traveled by a single tread. A 9-in run
  is the code minimum for main stairs. Total run
  is the measured distance from the beginning of
  the first tread to the end of the last tread-the
  horizontal length of the entire stairway

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Definitions

• Stairwell
• The framed opening in the floor that incorporates
  the stairs. Its long dimension affects how much
  headroom the stair has
• Stringboard
• Diagonal trim, not used to support the treads,
  that is nailed to the stair walls. Finished
  treads and risers butt these. Often called skirt
  boards, backing stringers, or plain stringers

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Definitions

• Tread
• It is both the horizontal distance from the face
  of one riser to the next, and the board nailed to
  the carriages that takes the weight of your foot.
  Exterior stairs, typically use 2x softwood
  treads. Interior stairs use either 1.5 in
  hardwood stock milled with a rabbet and groove to
  join it to the risers, or 13/16 in square-edged
  stock. Both are usually nosed

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Definitions

• Winder
• Wedge-shaped treads used in place of landing when
  space is cramped and a turn is required in the
  stairway. Many building codes state that treads
  should be at least the full width of the
  non-winder treads. 12 in from their narrow end
  or that the narrow end be no less than 6 in wide.

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Questions?
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Layout

• To lay out the carriages use the Pythagorean
  theorem (a2 b2 c2)
• Add the width of an extra tread to your total run
  to get enough length for the bottom riser cut
• Douglas-fir is the best lumber for the job
  because of its strength
• To draw the cut-out lines use either a framing
  square or a pitchboard

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Questions?
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Carriage Dropping

• Dropping the carriage is one of the most
  difficult things about stairs
• What you marked on the carriage is the top of the
  treads, but since you will be nailing treads to
  the carriages, you need to lower the entire
  member enough to make up for the difference
• If they sit on a finished floor such as a
  concrete basement slab, the bottom riser will
  need to be cut shorter by the thickness of a tread

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Carriage Dropping

• This will lower the carriage so that when the
  treads and upper floor finish are added, each
  step will be the same height. The bottom riser
  will have to be ripped to a narrow width
• If the treads and floor finishes are of equal
  thickness and the carriage sits on the subfloor
  at the bottom no change will have to be made for
  the risers to be equal

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Carriage Dropping

• When the treads are thicker that the finished
  floor draw a four-riser layout at any scale, on
  graph paper to figure how much of a drop you need
  to make and if the bottom riser needs to be
  narrower
• Give the carriage a trial fit before sawing it
  out.
• The treads should be level from front to back and
  the carriage should fit on both sides of the
  opening
• Make sure the risers will all be the same height
  once the treads and finish floor are installed

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Carriage Dropping

• For cut-out carriages use a circular saw as far
  as you can and finish them off with a handsaw
  held vertically so as not to over cut the line
  and weaken the cut
• Nail the triangular cutouts to a 2x6 for a third
  stringer as a budget cut
• Use the completed carriage as a pattern to trace
  onto the other 2x12 and then cut the pencil line
  to get an exact duplicate

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Questions?
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Tread and Risers

• On a closed stairway the cut-out carriages sit
  inside the finished wall stringers, called
  skirtboards or strings
• 1x10s nailed hard against the wall so that the
  snug fit of previously installed risers and
  treads arent spoiled by the skirtboards spreading

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Tread and Risers

• Install parallel to the noising line as high as
  possible
• Oak is best for treads but pine may be used
• Standard thickness for treads are 1 1/8 in and
  13/16 in
• Crosscut risers and treads 1 in longer than the
  inside dimension between the skirt boards

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Tread and Risers

• Risers will need at least a 45 degree miter to
  mate with the open stringer
• use a radial arm saw or handsaw for this

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Questions?
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Stair Assembly

• Stair assembly usually begins at the bottom
• First two risers are fit and nailed and then the
  first tread is pushed tightly against the bottom
  edge of the riser for scribing
• Treads are initially cut to overhang the open
  stringer by the same dimension as the nosing
• A cross-grain section is cut out so that a
  mitered corner is left at the outer edge

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Stair Assembly

• With a 1 in allowance for scribing set the
  scribers at 1/2 in for the first side
• Set the tread or riser with the side you are
  going to scribe down in place on the carriage and
  against the skirtboard
• The other end will ride high on the other skirt
• Snug the riser along its entire length
• Get the inside dimension at the back of the tread
  or lower edge of the riser depending on which you
  are fitting

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Stair Assembly

• Remember you can always plane it off but you
  cant stretch it
• Risers and treads are nailed to carriages with 8d
  finish nails through predrilled holes
• Three or four 6d common nails through the bottom
  of the riser into the back of the tread will keep
  stairs together

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Stair Assembly

• Two 1x1 blocks 2 in long glued behind each step
  at the intersection of the upper edge of the
  riser and the front of the tread will cut down a
  lot on movement too
• Any gaps between the carriage and treads should
  be shimmed from behind with wood wedges to
  eliminate squeaks

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Questions?