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Problems Of Existing Buildings |
Most of the existing buildings are built of masonry--brick, stone, terra-cotta, and concrete block.. Structures with all-masonry exteriors come to mind immediately, but most other buildings at least have masonry foundations or chimneys. Although generally considered "permanent," masonry is subject to deterioration, especially at the mortar joints. Also many structures are built to outdated codes of practice or mere custom and practice. All too often original drawings are not available. Brick or stone masonry is the oldest and most commonly used building material, yet it remains one of the least understood in structural terms. Various problems which dog the existing buildings are the problems of disintegrating mortar, cracks in mortar joints, loose bricks or stones, damp walls, or damaged plasterwork, etc. Cracking occurs as a result of tensile strain, which may be induced by deformation in bending and shear, or volume changes of the component bricks, blocks or mortar, arising from temperature or moisture induced expansion or shrinkage, corrosion, pollution or associated reactions. The root cause of the deterioration are the leaking roofs or gutters, differential settlement of the building, capillary action causing rising damp, or extreme weather exposure. Also old buildings were often built on soft soils, their builders were unaware of the future consequences. Anyway all categories of structures may suffer settlement through ground movement independent of the foundation loading. Such movements are typically caused by mining, tunneling, earthquakes, changes to groundwater levels, adjacent excavation and soil swelling and shrinkage.
Building codes developed with new construction in mind are difficult to apply rationally and predictably to existing buildings. Because developers and building owners cannot predict with certainty what will be required to bring a deteriorated building back into use, projects in existing buildings are often not attempted at all and the buildings remain unimproved.
Basing requirements for existing buildings on the standards for new construction causes several problems. In many cases, the requirements for new structures cannot be met in existing buildings. For example, it is difficult, if not impossible, to determine whether turn of the century lumber and bricks meet the current material standards in the code. New building requirements for stairway geometry (minimum tread and maximum riser dimensions) often mean that existing stairways are too steep and need to be replaced. Stairways with shorter risers and wider treads require more room and often cannot be fit into existing buildings without totally reconfiguring the space. Other new construction requirements that often cannot be easily met in existing buildings are ceiling height requirements, egress window requirements, and corridor and doorway width requirements.A second problem is predictability. Code officials recognize that making an existing building meet all of the requirements of the code applicable to new buildings is impossible. However, there is little consistency among code officials about which requirements are necessary to improve safety. A building owner often has no idea what will be required prior to submitting plans for review or meeting with the code official. A level of uncertainty remains because it is difficult to predict what obstacles will be encountered when trying to place a new building system into an existing structure. This uncertainty makes building owners hesitant to undertake building improvements because they cannot predict the cost of the project.
There are four categories of rehabilitation work: repair, renovation, alteration, reconstruction. Requirements are based on the category of work.
1) "Repair" means fixing a building component that is worn or broken. Under this category, materials and assemblies may be replaced with like materials and assemblies. There is no limit to how much repair may be undertaken in connection with a project. There are only a few specific exceptions to this rule. They include requiring certain products and practices, such as putting in a low flow toilet when a toilet is being replaced, and prohibiting other items, such as certain electrical materials or supplies.
2) "Renovation" is generally restorative in nature, such as the replacement of interior finish, trim, doors, or equipment, but involves the use of different materials. There is no reconfiguration of space. The materials used and the methods of installation must conform to the requirements found in the materials and methods section. The requirements set out in products and practices also apply.
3) An "alteration" project includes reconfiguring existing space. Products and practices and materials and methods requirements apply to alteration work. To address the possibility that the reconfiguration of space could create a safety hazard, there are some additional requirements for alteration work. These specify that the work undertaken cannot create a nonconformity with the basic requirements that did not exist before the alteration began.
This is a key issue to understand. In an alteration, the portion of the building being worked on does not need to be brought up to the standard established in the basic requirements. The basic requirements are used as a measuring stick. The work being done cannot make the building less conforming with the basic requirements than it was before the work was undertaken.
4) "Reconstruction" is a project consisting of the other categories of work where the work includes an entire tenancy (a portion that is under the ownership or control of one owner or tenant) and precludes occupancy during the project. This category involves extensive work to the interior of a building, floor, or tenant space. It is commonly referred to as a "gut rehab." Reconstruction includes repair, renovation, and/or alteration in any combination. Reconstruction does not include projects comprised only of floor finish replacement, painting or wall-papering, or the replacement of equipment or furnishings. Asbestos hazard abatement and lead hazard abatement projects are not classified as reconstruction although occupancy of the work area is not permitted.
Repair, renovation, and alteration work that make up a reconstruction project must comply with the requirements for the applicable category of work. The entire work area must comply with basic requirements. Certain reconstruction projects must also meet the supplemental requirements, which apply only when the work area for a reconstruction project exceeds a specific size, and it could include new building elements, depending on the scope of work.
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