Another type of door that cannot meet the test for fire rating under NFPA 252 is the honeycomb core (hollow-core) wood door, commonly used in residential and business occupancies http://sandsand.site90.net. This door is made up of two thin veneers of wood http://stroitel.net16.net separated by a honeycomb of thin wood or fiberboard strips.
Photo 2 shows the construction of a slab door with a particle-board core. This type of door is made of a slab of particle board (wood fibers and adhesive) with a wood veneer glued to both faces. This type of door can meet the test for fire ratings up to one hour according to NFPA 252 and is frequently used in fire-rated assemblies in residential and business occupancies.
Photo 3 shows the construction of a wooden slab door with a gypsum (kalamein) core. This type of door appears similar to a slab door with a particle-board core except that the core is gypsum material like that used in drywall board. http://stroitelstvo.comlu.com This type of door can meet the test for higher levels of fire rating under NFPA 252 than the particle-board core. This door type is frequently used in fire-rated assemblies in schools, patient-care facilities, and commercial buildings. It is also manufactured of steel instead of wood veneer and is filled with gypsum material.
Some older kalamein doors had a core of asbestos cement instead of gypsum. Although the asbestos core is no longer used because of the health hazard of asbestos, many of these doors are still present in structures built before 1980.
Добавлено (20.04.2013, 10:20)
From the general contractor's perspective, the good news is that America's demand for new commercial and residential building has been on the increase in 2005. http://plane.site11.com According to the U.S. Census Bureau of the Department of Commerce, as of August 2005 construction spending was estimated at a seasonally adjusted annual rate of $1,108.5 billion, 6.1 percent above August 2004. During the first eight months of 2005, construction spending amounted to $723.7 billion, 9.0 percent above the same period in 2004. From July to August 2005, the fastest growing segments of the construction industry were highways and nonresidential private construction, outpacing the rate of growth in residential and all other facets of public construction.
Demand for new construction is growing at a healthy, but not excessive rate, which should bode well for stable construction costs, right? Unfortunately, this is not the case. External forces have resulted in phenomenal rate increases for a wide range of integral construction supplies, raw materials and services. This fact has made the process for long term cost projections more difficult now than it's ever been.
Добавлено (20.04.2013, 10:22)
Buildings types that form residential neighborhoods are usually a mix of several types of homes with variations that are based on the category type and can be easily packaged, allowing for more standardized operations. http://buildbuild.vacau.com Although our old standbys should be understood, our new neighbors may not fall into easily adapted operational patterns. Many new buildings are vastly different in their layouts, and even the most diligent of firefighters would be unable to remember all the variations.