Make HowStuffWorks your home page!

Mobil Travel Guide | Consumer Guide Products | Consumer Guide Auto

Search HowStuffWorks and the Web

Auto Stuff Science Stuff Health Stuff Entertainment Stuff Travel Stuff
Computer Stuff Electronics Stuff Home Stuff Money Stuff People Stuff Shop for Stuff

Main > Home > Home Improvement

Click here to go back to the normal view!

How House Construction Works

by Marshall Brain

In the United States, there are more than 100 million housing units, and the majority of them are
"single family dwellings," or houses. In cities, in the suburbs and in rural communities, houses are a
very common sight.
Have you ever wondered how a house is built? What holds up the ceilings and the walls? What keeps
the rain out? What parts go into making a house? How many different people are involved when a
house goes up? If you would like to know the answers to questions like these, or if you have simply
been curious to know all the steps that go into making a new home, then read on. In this article, you'll
learn exactly how houses are built.
 Happy homebuilder?
Have you built your own house?
How did you do it?

Share your experience.

Setting the Stage

So let's start at the beginning. What is a house? According to The American Heritage Dictionary of the
English Language, a house is "A structure serving as a dwelling for one or more persons, especially
for a family." You probably have a very specific mental image of the "typical house." It is a structure on
its own piece of land, generally with a lawn and plants outside. It has a pitched roof, walls covered in
brick or siding, windows and doors. Inside there are rooms like the kitchen, the living room, bedrooms
and bathrooms.

I can show you a hundred pictures of houses and they may all be completely different in their
specifics, but they will all share those basic characteristics.

Steps to Building a House

One of the amazing things about American homes is that the huge majority of them are built using
completely standardized building practices. One reason for this consistency is a set of uniform building
codes that apply across the country. Another reason is cost -- the techniques used to build homes
produce reliable housing quickly at a low cost (relatively speaking). If you ever watch any house being
built, you will find that it goes through the following steps:

● Grading and site preparation

● Foundation construction
● Framing
● Installation of windows and doors
● Roofing
● Siding
● Rough electrical
● Rough plumbing
● Rough HVAC
● Insulation
● Drywall
● Underlayment
● Trim
● Painting
● Finish electrical
● Bathroom and kitchen counters and cabinets
● Finish plumbing
● Carpet and flooring
● Finish HVAC
● Hookup to water main, or well drilling
● Hookup to sewer or installation of a septic system
● Punch list

Many of these steps are performed by independent crews known as subcontractors. For example,
the framing is generally done by one subcontractor specializing in framing, while the roofing is done by
a completely different subcontractor specializing in roofing. Each subcontractor is an independent
business. All of the subcontractors are coordinated by a contractor who oversees the job and is
responsible for completing the house on time and on budget.

We will walk through these different stages so that you can see what is involved, understand all the
steps and learn about the different materials used in the construction process. We will use a typical
three-bedroom home as our example.
Site Preparation
The first crew on the site handles site preparation. Often, this crew and the foundation crew are the
same people, but sometimes not (especially if there are a lot of trees on the lot). Houses are generally
built on a foundation that is either a basement, a crawl space or a slab. The site-preparation crew
typically arrives on the site with a backhoe and/or bulldozer. The crew's job is to clear the site of any
trees, rocks and debris, level the site if necessary and dig as necessary for the foundation being built.

The example house shown here is built on a crawl space. For a crawl space, the site preparation crew
digs a set of trenches and holes. Concrete is poured into these trenches and holes and will act as the
interface between the foundation wall and the ground. Once the concrete is poured, the house looks
like this:
(In these pictures, the bricks for the crawl space have already been moved into position while the
concrete cures.) The concrete in the trench is generally about 18 to 24 inches wide (45.72 to 60.96
cm) and 18 to 24 inches deep. Once it hardens, it forms a massive concrete "beam" on which the
house rests. The width of this concrete beam is controlled by the compressibility of the soil. In light
soils, the beam will be wider to try to spread out the load, while in heavy clay soils it can be narrower.

If the site slopes, the concrete beam is stepped, like this:

Concrete takes approximately four weeks to cure to full strength (depending on the weather), so once
the concrete is poured nothing will happen for some period of time while the initial curing takes place.

If this house had been built on a basement, the site-prep crew would have dug a square hole about 8
feet deep. If this house had been built on a slab, the site-prep crew would have trenched around the
outside approximately 2 feet deep and then completely leveled the area for the pad.

Foundation
Slabs, basements and crawl spaces are the three main foundation systems used on houses. In wet
and coastal areas, it is sometimes common to put houses up on posts as well.

Slab
The slab is probably the easiest foundation to build. It is a flat concrete pad poured directly on the
ground. It takes very little site preparation, very little formwork for the concrete and very little labor to
create. It works well on level sites in warmer climates -- it has problems up north because the ground
freezes in the winter and this freezing can shift the slab at worst and at least lead to cold floors in the
winter. A cross-section of a typical slab looks like this:

Around the edge of the slab, the concrete forms a beam that is perhaps 2 feet deep. The rest of the
slab is 4 or 6 inches thick. A 4- or 6-inch layer of gravel lies beneath the slab. A 4-millimeter sheet of
plastic lies between the concrete and the gravel to keep moisture out. Embedded in the concrete is 6-
inch by 6-inch wire mesh (shown by the dotted line in the slab) and steel reinforcing bars (shown by
the white circles at the bottom of the beams). You will often hear this sort of foundation referred to as
a "floating slab" -- it "floats" on the soil, with the deeper concrete around the edge holding it in place.
In northern climates, the concrete around the edge has to extend deep enough to remain below the
frost line in winter.

One thing about a slab is that the sewer pipe, and sometimes much of the electrical conduit, has to be
put in place before the concrete is poured. The sewer pipes are actually embedded in the slab.

Basement
A house with a basement starts with a hole about 8 feet deep. At the bottom of the hole is a concrete
slab, and then concrete or cinder-block walls form the outer walls of the basement. Actually, a
basement is poured in three pieces in most cases: the "beams," then the walls, and then the slab
inside the walls, like this:
This approach helps keep the basement waterproof. The L-shaped piece is a steel reinforcing bar to
bind the beam and the wall together.

Crawl Space
A crawl space has several advantages over basements and slabs:

● It gets the house up off the ground (especially important in

damp or termite-prone areas).
● It is a lot less expensive than a basement and comparable in
price to a slab.
● Duct work and plumbing can run in the crawl space, meaning
that they are easy to service and move over the lifetime of the
house.

Most of the time, a crawl space is made of cinder block with a brick
facing, as shown in the image on the right.

This is exactly how our sample house is put together. Here is how the
finished foundation looks:
You might have noticed in the previous pictures that the concrete
work for the crawl space was not done with much precision at all.
One of the neat things that the mason (bricklayer) does is carefully
adjust the height of the cinder blocks and bricks with mortar thickness
so that the crawl-space walls end up exactly level all the way around.

One problem that arises in crawl spaces and basements is dampness. In order to keep water out,
perforated pipe and gravel are used in a trench around the crawl space to route water away. The
drainage system looks like this:
In a house with a basement, this same sort of drainage system is added along the bottom of the walls.
The basement walls are then generally insulated with rigid foam board and then heavily waterproofed
before dirt is backfilled against the walls.

Floor
The framing crew is the next group of people on the site. They start by building the floor (unless the
house uses a slab foundation, in which case the slab is the floor). The floor framing looks like this:
The floor starts with a sill-plate made of pressure-treated lumber in direct contact with the bricks of the
crawl space wall. One interesting thing to note is that this house literally "sits" on the foundation -- it is
not held on or bolted on in any way. Then the floor is constructed on the sill with 2x10 lumber:
You may have noticed the brick posts when you saw the picture of the foundation. They hold a beam
that runs down the center of the house. The beam is also built from 2x10 lumber (three pieces thick):
All of the "joists" (as the 2x10s in the floor are called) meet on this center beam:
(In many houses the meeting of the joists is somewhat better organized!)

This funny little cantilevered section of the frame will eventually hold the fireplace:
Once the floor framing is complete, it is covered with 1/2-inch or 5/8-inch plywood or OSB (oriented
strand board).

And the floor is finished.

Walls
The framing crew next starts on the walls. Walls are assembled on the floor...
...and then raised into place. Here's what the first wall looks like once it is up:

You can see that this wall is made of 2x4 lumber and covered on the outside with an OSB sheathing.
Using plywood or OSB as the sheathing gives the wall rigidity -- you may have seen diagonal pieces
used at the corners of older homes (homes built before plywood was widely available). The plywood
does the same thing, but it provides much more strength.

The 2x4s are placed on "16-inch centers," meaning that the center of one 2x4 is 16 inches away from
the center of the next. In this wall, two things interrupt the consistent 16-inch pattern:

● Windows
● Special framing that will accommodate internal walls once they are built

Here's a shot that shows these two features in better detail:

The plywood will be cut out of the window openings as construction proceeds. Above the window is a
2x10 header, which is actually two 2x10s with a piece of 1/2-inch-thick plywood sandwiched in
between and a 2x4 along the bottom:
 A cross section of a header is shown at the right. The reason why the header has
plywood in the middle is simply to make the header as wide as the rest of the wall. A
2x4 is really 1-1/2 inches by 3-1/2 inches, and a 2x10 is really 1-1/2 inches by 9-1/2
inches. When you sandwich two 2x10s together they are only 3 inches wide. Adding
the piece of plywood in between makes the sandwich 3-1/2 inches wide.

A 2x10 header is a beam. You see these headers over all windows and doors -- they
give the wall enough strength over the window or door to support the roof. When a
header spans more than 5 feet, you find double full-length studs on either side of the
header instead of the single studs seen here.

All of the exterior walls go up following this same basic pattern. In the corners, the
top plate on one wall overlaps the top plate of the next, and the walls are nailed
together to bind the corner. Then the interior walls go up, fitting into the top plates of the exterior walls
as shown above.
This house has a garage and a breezeway connecting the garage to the house.
The walls of the garage are built slightly differently (because the garage will have a slab floor). The
walls are bolted directly to the brick foundation walls:

Here's how the house looks right before the roof framing starts.
You can see that the framers have covered the outside walls in pink house wrap.

Roof
This house uses trusses for the roof framing. Trusses are pre-fabricated, triangulated wooden
structures used to support the roof. The alternative is to build up the roof's frame with 2x8s and 2x10s.
Trusses are quite common these days because they have five big advantages from the builder's
standpoint:

● Trusses are incredibly strong.

 ● Because they are built strictly from shorter lengths of 2x4 lumber, they are generally a lot less
expensive than the alternative.
● You can have just about any shape custom-built, and this allows interesting features like
cathedral ceilings at low cost.
● You can span a large distance with a truss and the truss transmits all of the weight to the
exterior walls. Therefore, none of the interior walls are "load-bearing," so they can go anywhere
and are easily moved later.
● Trusses go up quickly!

From the homeowner's standpoint, the one big disadvantage is that you don't have any attic space.
C'est la vie...

Trusses come in several standard configurations:

"W" truss

"M" truss
 "Scissors" truss

"Gable" truss

Gable trusses are used at the ends of the roof (the outermost trusses on either end). The vertical
pieces are 16 inches on center so that siding can be nailed on. Our sample house uses a custom
truss in the main part of the house that looks like this:

The left-hand side will provide a cathedral ceiling over the living room. Scissors trusses are used for
the front room, and M trusses are used over the garage. Gable trusses are used at the ends of the
three rooflines.

The trusses are fist stacked on top of the walls, either by hand or with a crane.

These trusses went up in about four hours. They are on 24-inch centers.
The trusses are tied to the walls with small metal plates.
Once the trusses are up, the roof is covered in plywood or OSB, which gives the roof tremendous
rigidity.
There are two small custom roofs in this house: the roof over the porch (see next section) and the roof
over the breezeway.
Roof framing without trusses is actually fairly complicated. The angles found in anything but the
simplest roof become intricate. A book like Do It Yourself Housebuilding by George Nash goes into
roof framing in incredible detail.

Porch
The crew built the porch, starting with the frame.

Then a floor goes on top of the frame.

Here are the trusses of the roof over the porch:

Windows and Doors
Inside the house, things are now beginning to look enclosed:

The next step in enclosure is windows and doors. The windows and doors arrive in one shipment and
are unloaded from the truck into a stack:
Plastic stripping is stapled to the inside of all window and door openings, like this:
The windows used here are standard vinyl windows. They are placed in each rough opening and
stapled in place on the outside.
The front-most window is the feature window of this house:

Roofing
This house uses standard asphalt shingles for the roof. The first step is to cover the roof with building
paper (tar paper):
The shingles then go on very quickly (on this house, in less than a day):

In the following shot you can barely detect the ridge vent that runs along the peak of the breezeway
roof. There is a vent like this along the peak of all the roofs.
This vent replaces the triangular "gable-end vents" found in older homes. Ridge vents give better
circulation (especially when cathedral ceilings are used) and also prevent bats and squirrels from
getting into the attic.

In the following shot, you can see the aluminum flashing that keeps water away from the walls at the
points where the shingles touch the walls.
At the edge of the roof, the shingles are cut off with about 2 inches of overhang:

Siding
This house uses standard vinyl siding. The siding is made from thin, flexible sheets of plastic about 2
millimeters thick, pre-colored and bent into shape during manufacturing. The sheets are 12 feet long
and about a foot high. You start at the bottom and the sheets interlock into each other as you go up.
Because vinyl expands and contracts due to temperature and sunlight, it fits into deep channels at
the corners and around windows and doors. The channels are deep enough that as the siding
contracts it remains within the channel. The following shot shows a channel nailed to a corner of the
house and a piece of siding fitting into it. It is nailed in place and ready for the next sheet to be
interlocked and installed above it:

This is the back wall of the house, showing the scaffolding used to install the siding:
This shot shows roofline detail. The area extending out from the house under the roof is known as the
soffit (parallel to the roof). The fascia boards are perpendicular to the roof. The soffit is perforated so
that air can flow into the attic and up through the ridge vents to ventilate the attic. In this shot, part of
the soffit is in place, while part is awaiting installation. Note that all exposed fascia wood is capped
with a sheet of painted aluminum that was bent into shape on the site:
At this point, the house is "dried in," meaning that it is completely protected from rain. Now interior
work can begin.

Plumbing
Let's say you want to put a toilet in a house. Two-hundred or 300 years ago this was not an option --
everyone used outhouses. If you visit the governor's mansion in Williamsburg, VA, you will see that in
the 1700s even England's high colonial governor used a pair of three-holer outhouses located at the
back of the formal garden. Eventually, public water supplies and pressurized well systems allowed
people to have indoor plumbing, and this allowed for the addition of indoor toilets. A toilet has to flush
somewhere, so sewer systems evolved.

Why can't you run the sewer line from a toilet or a sink out of the side of the house so it spills on the
ground? That certainly would be easy and inexpensive, but people learned fairly quickly that human
waste spilled on the ground smells bad and leads to incredible disease problems. Septic tanks and
sewer systems take care of this. The uniform plumbing code lists hundreds of rules for septic-tank
installation. These rules ensure that tanks work properly over many years.

Once you have a septic tank in place, you can add sewer lines from the sink or toilet to the septic
tank. Say you tried this approach:
The problem with this approach is that as the septic tank fills up with stuff, it produces a rather
malodorous cloud of fumes. These fumes float from the septic tank up the sewer line to the sink and
into the bathroom. Therefore, plumbing codes require a "P-trap" at every drain opening, as shown
here:

You may have wondered why you find these funny loops of pipe under every sink in your house. The
idea is that water gets trapped in the "P." This water blocks the fumes from the septic tank and keeps
them from entering the bathroom. Unfortunately, a P-trap alone does not solve the problem because it
turns out that the fumes in a septic tank are under pressure. The fumes simply bubble through the
water in the trap and cause the same problem. Therefore, there is the concept of a vent pipe, which
allows the pressure to escape, as shown here:
You may have wondered why houses have pipes sticking up out of the roof. They are vent pipes to
relieve the pressure so that P-traps can do their jobs. It turns out that vents also break vacuums so
water flows down the pipes faster.

Besides covering P-traps and vent pipes, the uniform plumbing code specifies all sorts of other things:

● The required diameters for pipes

● The allowed materials for pipes
● The types of joints you can use
● The necessary supports for pipes
● The angle at which pipes must fall
● The longest distance for lateral pipes
● And on and on and on through hundreds of pages

When plumbers follow all the rules, they are able to create extremely reliable and safe plumbing
systems. Over time, new rules get added as people realize funny little quirks and nuances. These new
rules prevent problems in the future, and each one makes the code a little bigger and better.

This is all a nice way to say that, even though plumbing looks simple in this section, there are many
subtleties and nuances dictated by code that plumbers know and neophytes generally do not. (The
same holds true for electrical systems, by the way.)

Rough Plumbing
Rough plumbing involves installing all of the water lines, sewer lines and bathtubs. Tubs are normally
installed early because:

● One-piece shower-and-tub units are big and often cannot be maneuvered into place later in the
construction cycle. They also frequently "change size" -- that is, the size drawn on the plans and
the size delivered often differ significantly.
● A full tub is heavy. Therefore, the tub is installed and filled so that the frame can settle quickly.
This step prevents cracked walls and tile the first time someone uses the tub.

Typically, rough plumbing involves installing all sewer lines and vents as well as all water supply lines
for each fixture. Here's a typical sink fixture:

Here's the fixture for a washer:

The tub is put in place and filled. Note the framing problem being corrected on the left side of the tub
because the tub changed size:
Here are the lines for the tub:

In the crawl space, the supply lines all branch off from common pipes running the length of the house:
The sewer lines all join together...

... and then exit out the back of the house, ready for connection to the septic tank:
Rough Electrical
The article How Power Distribution Grids Work goes into extensive detail on how power gets from the
power plant to your house. The purpose of the electrical system in a house is to distribute the power
safely to all of the different rooms and appliances.

The electrician for this house first placed all of the boxes for electrical outlets, lights and switches:

Then he ran wires from the fuse box to each box and between boxes. Here's what the fuse box looked
like once he got done:
Wires were first run through to the boxes. A lot of drilling is necessary, both down into the crawl space
and up into the ceiling, as well as through studs to run wires between boxes:
Wires are then pulled through the boxes, clipped and capped:

This shot shows the water line for the refrigerator's ice maker as well as the refrigerator's electrical
line. Note the use of metal reinforcing plates at all holes (also visible in the shot of the fuse box
above):
Insulation
The purpose of insulation is to lower the heating and cooling costs for the house by limiting heat
transfer through the walls and the ceiling. The insulation process starts by installing foam channels in
the eaves:
These channels guarantee that air will be able to flow from the soffit vents to the ridge vents. Without
these channels, insulation tends to expand into the eaves and block the soffit vents. This house uses
standard fiberglass insulation throughout:

Notice that over the insulation is a thin plastic vapor barrier. The idea behind the vapor barrier is to
keep moisture that develops inside the house inside. Without the barrier, here is what happens inside
the wall in winter: Warm, moist air moves through the drywall and into the insulated wall cavity; at
some point inside the cavity it becomes cold enough for the moisture to condense, soaking the
insulation. The vapor barrier prevents this process. In older homes, the siding and sheathing were so
loose that air easily migrated out before the moisture condensed, but that is no longer the case so the
barrier is essential.

Drywall
On the outside, the house now looks complete; but inside, it won't look "like a house" until the drywall
goes up. Drywall (also known as "plaster board" and by the trade name "Sheetrock") is a half-inch
layer of plaster or gypsum sandwiched between two thick sheets of paper. It is remarkably solid, and
also remarkably heavy.

To finish this house, 134 sheets of drywall measuring 4 feet wide by 12 feet tall were delivered to the
site and stacked in the living room:

A 4x12 sheet of drywall weighs about 50 pounds (23 kg). So this room has about 6,700 pounds (about
3,000 kg) of drywall stacked in it!

The drywallers put up all of the drywall in a day and taped it the next day:
To "tape" the drywall means to cover all of the cracks and nails with drywall mud (spackling
compound) so that the walls are completely smooth. You can see that the cracks and nails are all
covered in the pictures above.

Garage Slab
The floor of the garage is a 4-inch-thick concrete slab poured very late in the process. Four inches of
gravel were placed on the ground and covered with plastic and reinforcing wire. Around the edges,
half-inch thick homosote will allow the slab to contract and expand with temperature changes. Once
the prep work was finished, a concrete truck came and poured about 7 cubic yards of concrete to
create the slab.
Finishing Up
At this point, the steps that remain are all "finishing steps" and are things you can see in your own
home by opening doors and removing cover plates. The finishing steps include:

● Putting down underlayment - The plywood put down during the initial framing is called
subflooring. Generally it is covered by tar paper or 4-mil-thick plastic as a vapor barrier and
then by 5/8-inch particle board. Alternatively, it may be covered with rigid concrete wonder
board for tile installations.

● HVAC - Once the underlayment is down, the HVAC contractor will install the heating and air
conditioning unit (aka the furnace), the vents and all duct work. If this had been a two-story
home or a home built on a slab, the HVAC people might have had to install some ductwork in
the walls or between floors. However, in a single-story home on a crawl space or basement, the
furnace and all ducting can go in very late in the process because everything goes under the
house.

● Finish electrical - The electrician will return and install all light fixtures, wall outlets, switches
and cover plates.
 ● Kitchen and bathroom cabinets and counters - The cabinet company will install kitchen and
bathroom cabinets. They are simply aligned on the wall and screwed into the wall studs.
Countertops are screwed on top of the cabinets.

● Finish plumbing - Once the cabinets are in, the plumber will return and install sinks, toilets and
faucets. The plumber will also install the water heater if it was not installed during rough
plumbing.

● Installation of well and septic system or hook-up to city water and sewer - Depending on
where the house is located, it will either have a private well and septic system or it will hook up
to municipal water and sewer lines. If a private well and septic tank are needed, the contractor
will bring in a well-drilling subcontractor and a septic-tank subcontractor. Otherwise, the
contractor will call someone (either the municipality or a subcontractor) to extend the municipal
lines to the house. The plumber will hook up the water and sewer lines.

● Wall trim - Once the cabinets are in, the interior doors are installed and the molding around the
doors, windows and baseboards goes in.

● Paint - Once the molding is on, it is time to paint and wallpaper the interior of the house.

● Carpeting and tile - Once the paint is done, carpet and tile goes down.

● The final punch list - At this point, the builder inspects the house, noting any problems. All
problems are tabulated on a punch list. The different contractors return to fix all of the
problems.

Once the punch list is done, it's time to move in! Here are some shots of the finished house:
This article has shown you the basic steps involved in house construction. Obviously there are a lot of
details that we have omitted here, as well as a huge number of rules embodied in the building codes.
If you want to learn more, I would recommend the excellent book titled Do It Yourself Housebuilding,
by George Nash.

The next time you walk into a house or start poking around under it, I hope you do so with a much
better understanding and appreciation for everything that goes into making it work!

Lots More Information

Related HowStuffWorks Articles

 ● How Nail Guns Work
● How Chain Saws Work
● How Caterpillar Backhoe Loaders Work
● How Caterpillar Skid Steer Loaders Work
● How Hydraulic Cranes Work
● How Sewers and Septic Systems Work
● How Wires, Fuses and Connectors Work
● How Smart Structures Will Work
● How Smart Windows Work
● What causes the loud banging noise in my home's pipes?
● How does pressure treated lumber work?
● What is plywood? Why do people use it so much? What about oriented strand board (OSB)?
● What is this bumpy stuff on my ceiling that looks like popcorn or cottage cheese?
● Why do the entry doors to most homes open inward, while in most public buildings, the entry
doors open outward?

Partner Links

● Your House Works Part 3 of a PM Series: Framing

Sponsored Links

● Entry Doors
● Home Construction, Free Directory
● Home Renovation Resource
● House Painting
● Flooring, Decking, & Siding for Less

More Great Links

● HomeToolz - for do-it-yourself projects

● Sound Home Resource Center - a source for information on home construction and other topics
● HouseNet - advice, projects and tips
 ● Today's Homeowner: Expert Advice On Improving Your Home
● Home Building Manual
● E-Plans - a resource for house building
● B4UBuild
● COOLhouseplans.com
● House Plans and Home Designs by Rick Garner

Home Store Newsletter Search Advertising Privacy Terms and Conditions Contact About Help
© 1998 - 2006 HowStuffWorks, Inc.
Howstuffworks "How does pressure-treated lumber work?"

Make HowStuffWorks your homepage | Get Newsletter HowStuffWorks.com

RSS

Search HowStuffWorks and the web:

Home and Garden Home Improvement Remodeling

PRINT
EMAIL

How does pressure-treated lumber work?

Wood is a great building material. It is strong, lightweight, easily worked with
tools and relatively inexpensive. The only problem with wood is that many
varieties of bacteria, fungi and insects find it appetizing. When wood is in
Remodeling can make your contact with the ground or moisture for any period of time, these organisms
home more comfortable,
more beautiful and more attack the wood. Untreated wood like pine will only last a year or two if it is
marketable. Learn how to touching moist ground.
design and build remodeling
projects. Pressure-treated lumber is wood that has been immersed in a liquid
Related Categories: preservative and placed in a pressure chamber. The chamber forces the
> Tools & Materials chemical into the wood fibers. The pressurized approach makes sure that the
> Home Office chemical makes it to the core of each piece of wood -- it is much more
> Household Safety effective than simply soaking the wood in the chemical.
> Painting
> Plumbing
The most common chemical used to treat lumber used to be chromated
> Drywall and Plaster copper arsenate, or CCA. In 2003, however, the Environmental Protection
> Energy Efficiency Agency restricted the use of CCA in residential settings due to health and
> Patio & Porch environmental concerns about arsenic leaching out of the wood. The most
> Decorating widely used alternative to CCA is alkaline copper quat, or ACQ. Copper is
> Flooring toxic to various insects and fungi that might cause decay. ACQ binds to wood
> Furniture Restoration fibers very well and allows wood to last decades even when it is in contact
> General Repairs
with the ground.
> Heating & Cooling
The protection provided by the chemical depends on the amount of chemical
that the wood absorbs. In the United States, the amount of chemical is
RELATED AD CATEGORIES measured in pounds of chemical per cubic foot of wood. For ground contact,
Pressure Treated Wood
0.40 pounds per cubic foot is needed. For foundations, 0.60 pounds per cubic
Coated Wood
foot is the standard.
Plastic Wood

Polymer Wood The chemicals in treated wood are generally not good for humans. This is why
Wood Preservative you see warnings advising you to wear gloves, avoid breathing the sawdust,
and refrain from burning treated wood. Keeping small children away from
http://home.howstuffworks.com/question278.htm (1 of 3)2007-08-09 22:19:49
Howstuffworks "How does pressure-treated lumber work?"

treated wood is also a good idea.

REFERENCE LINKS These links will help you learn more:

● USDA Forest Service: Frequently Asked Questions about Wood

Did you know total distance of Preservation
the interstate is 42,794 mi?
● EPA: Chromated Copper Arsenate (CCA) and Its Use as a Wood
Preservative

● How House Construction Works

● What is the difference between a hardwood and a softwood?
● What is plywood? Why do people use it so much? What about
oriented strand board (OSB)?

Ads by Google

● Northern White Cedar

Premium White Cedar for siding, decking, furniture and more
business.vermont.com/bprobinson/

● wood impregnation plants

plants for pressure, low pressure, creosote impregnation of wood
www.moldrup.com

● Deck Screws - Wood Screws

No splits, pre-drill or mushrooming Fine hardwoods, composite, &
pine
www.splitstop.com

Share This Article: (what's this?)

More Options:

http://home.howstuffworks.com/question278.htm (2 of 3)2007-08-09 22:19:49

Howstuffworks "How does pressure-treated lumber work?"

ADVERTISEMENT

●
RELATED CONTENT

EXPLANATIONS

What is plywood? Why do people use it

so much? What about oriented strand
board (OSB)?

What is the difference between a

hardwood and a softwood?

How House Construction Works

Search HowStuffWorks and the Web

HSW Brazil | Home | Company Info | Advertise With Us | Newsletter | Careers | Privacy | Contact Us | Help | Terms & Conditions RSS

© 1998-2007 HowStuffWorks, Inc.

http://home.howstuffworks.com/question278.htm (3 of 3)2007-08-09 22:19:49