Construction of a House Cont'd

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.

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.
  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!

Construction of a House Cont'd

Rough Plumbing-
Rough plumbing involves installing all of the water lines, sewer lines and bathtubs. Tubs are normally installed early. 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. The tub is put in place and filled. 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. 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.

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.

Construction of a House Cont'd

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 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. 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 to put a pipe straight from the sink to the septic tank. 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. 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. 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.)

Construction of a House Cont'd

Porch-
The crew builds the porch, starting with the frame. The frame goes on top of short brick (or another sturdy material) pillars. Then a floor goes on top of the frame. That's it.

Windows and Doors-
Inside the house, things begin 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 the window and door openings on the house structure. A common window used is a standard vinyl window. They are placed in each rough opening and stapled in place on the outside.

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 (sometimes in less than a day). There is a vent along the peak of all the roofs that acts as a vent to allow hot air travel up and out of the house. This object is called a ridge vent. 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. The aluminum flashing 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.

Construction of a House Cont'd

Roof-
Some houses use 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. 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 situation: the roof over the porch 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.

Construction of a House Cont'd

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 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. The brick posts 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 the center beam. (In many houses the meeting of the joists is somewhat better organized!) A 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. The 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
  

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. 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. The headers over all windows and doors 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. 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. Some houses have 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. The framers sometimes cover the outside walls in pink house wrap.

Construction of a House Cont'd

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. 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. Noticedthat 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. 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.