Blog Archives

Metals

Posted by on 16/ 11/ 15

Metals

Oil Residue on Metals

Expanded metal lath and other metal goods are often shipped to sites coated in rancid oil residues left over from the manufacturing process. Such residues will be odorous for a prolonged period of time unless the metal is cleaned. When these oils are left in metal duct­work, hot air blown through the ductwork distributes these odors throughout the house. To avoid this unwanted pollution source, con­sider adding the following to your specifica­tions:

• Remove oil residue from all coated metal products using a high-pressure hose and one of the acceptable cleaning products listed in these specifications.

Some builders have found that the high-pres­sure hoses at self-service car washes are effec­tive for removing oil residues.

Metals and Conductivity

The role tha...

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Welded Steel Plate Girder Bridge

Posted by on 16/ 11/ 15

The welded steel plate girder bridge (Fig. 4.9) extends the span range of deck-type bridges (bridges having all the structural support below the deck slab) well beyond the range of rolled steel beams or precast prestressed-concrete beams.

37-0"

Welded Steel Plate Girder Bridge

Whereas haunched girders were economical in the past for long spans, the current practice, strongly advocated by the steel-fabricating industry, is to use parallel-flange girders wherever possible. This is an economic consideration rather than an aesthetic one. Properly configured haunched girders are thought by many to be more pleasing. They permit a shallower structure depth at mid span, which can result in a lower grade line and consequent savings in roadway construction cost...

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The stationarity assumption

Posted by on 16/ 11/ 15

Viessman et al. (1977, p. 158) noted that “usually, the length of record as well as the design life for an engineering project are relatively short compared with ge­ologic history and tend to temper, if not justify, the assumption of stationarity.” On the other hand, Klemes (1986) noted that there are many known causes for nonstationarity ranging from the dynamics of the earth’s motion to human- caused changes in land use. In this context, Klemes (1986) reasons that the notion of a 100-year flood has no meaning in terms of average return period, and thus the 100-year flood is really a reference for design rather than a true reflection of the frequency of an event.

3.9.2 Summary comments

The original premise for the use of hydrologic frequency analysis was to find the optimal project...

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Housewraps Are Susceptible to Certain Chemicals

Posted by on 16/ 11/ 15

Builders have debated the chemical compat­ibility of housewrap for years. Studies have found that certain types of wood siding, like cedar and redwood, leach surfactants (surface-active contaminants) that can affect the water resistance of housewraps. The sur­factants reduce the surface tension of water, easing its ability to pass through micro­scopic openings in the membrane. To com­bat the problem, manufacturers recommend back-priming potentially troublesome wood siding with a water-repellent primer. In a
limited study, Fisette found that the newest version of Typar had superior resistance to surfactants compared to the performance of similar products.

In addition to the water-soluble extractives found in wood siding, the water resistance of housewrap also can be compromised by soaps,...

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FRAMING FLOORS

Posted by on 16/ 11/ 15

When a carpenter first arrives at the job site, the foundation is often poured and ready for sill plates, joists, and floor sheathing. Just make sure you’re building on the right foundation. I once started building on the wrong lot in a tract of houses. My crew was well under way when the owner of the property arrived and said he appreciated our efforts but wasn’t intending to build just yet

CHECKING THE FOUNDATION

Like most things in life—from cooking to marriage—if you get started right, things just seem to go better the whole way. This is certainly true in construc­tion. So before attaching the wooden sill plates to the foundation, you must be sure that the foundation itself is accu­rate. Problems get worse by the day unless you get started square, plumb, and level.

Begin with a v...

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Flow, Transport and Transformation Processes

Posted by on 16/ 11/ 15

Road and traffic pollutants are emitted in gaseous, solid or liquid form.

Materials used for the construction of pavements and embankments contain pol­lutants mainly in the solid state. However, pollutants initially in the solid state can be released into water. Two processes are at work:

• desorption – chemicals are detached from the solids to which they are loosely bound, and

• dissolution – chemicals are dissolved by adjacent water. Together these are known as leaching.

Pollutants will move from the solid phase to the dissolved phase until:

• The water cannot hold more (“solubility limit”); or

• There is no more solid phase to be desorbed or dissolved (“source limit”); or

• There is insufficient contact time for the processes of desorption or dissolution to complete (“a...

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SHELTER

Posted by on 16/ 11/ 15

A Roof Overhead

The walls for our house are up and we now have something to show for our work. At this stage, we can walk through the structure; admire the view through rough window openings; and imagine how the finished siding, painted drywall, and flooring will look. But first, we need to raise the roof.

Before we reach for a hammer, we need to make some decisions about the roof trusses. We also have to prepare the site for their delivery and do some layout work so that the installation process can go smoothly. Once the trusses are installed, we’ll move on to the fascia boards, sheathing, and shingling.

Roof Trusses

Early in my building career, I was taught how to lay out rafters with a site-made template containing the plumb and bird’s-mouth cuts...

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Basic floor plan

Posted by on 16/ 11/ 15

 

Basic floor planBasic floor plan

this plan is on paper, you can start to figure out how to build the project and calculate what materials you will need.

House plans are like road maps. If you want to drive from Oregon to New York, for example, you look at a map. You know you can’t visualize everything you will see along the way, but if you follow the lines and symbols properly, you will arrive at your destination. The same goes for building: Learn to follow the plans step-by-step, and you will com­plete the project.

Scale and dimensions

When reading plans or doing layout on a building, pay attention to the scale of the drawings and how the dimensions are marked. These are critical to making a good estimate of materials and to building the structure.

If house plans were drawn full size, you would need very large ...

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TIGHTENING NEWEL POSTS

Posted by on 16/ 11/ 15

If many of the balusters are loose, check the rail­ing and the newel post: They may not be firmly attached. Or if the upper end of the railing dead ends into a wall on the floor above, the railing may be anchored with a bracket beneath. Make sure this bracket is tight.

If the newel post is shaky, try shimming underneath its base or screwing the post down

Anatomy of a Hollow Newel Post

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Unlike modern newel posts, older ones are often hollow and attach to railings in various ways. One common way is a star nut centered in the end of a railing, which is accessed by removing a plug on the underside. The bottom of the post may be screwed to a stringer or held fast by an adjustable rod-and-plate assembly running down the middle of the post.

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This three-piece railing assemb...

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Water, Insects, Rot, and Mold

Posted by on 16/ 11/ 15

Whether structural damage is caused by insects or rot fungi, excess water is usually the heart of the problem. Thus, before treating the specific agent causing the deterioration, reduce excess water by maintaining gutters, improving drainage, grading the soil away from the building, eliminating wood-soil contact, improving ventilation, and so on.

The fungi that rot wood reproduce by airborne spores, so they’re virtually every­where. But they can’t establish colonies on wood with a moisture content (MC) less than 28 percent; and they go dormant if the MC drops below 20 percent or the air temperature drops below 40°F. Household molds, also caused by fungi, thrive in a similar moisture and temperature range...

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