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Home Construction
- Materials Storage
- One of the most important elements in mimizing building maintenance and preserving the potential life of a structure will be the care with which the materials of construction are handled. Most manufacturers strongly recommend protecting wood products from the elements on a job site by avoiding ground contact, and by providing cover from precipitation.
- All wood products brought to the job site should be:
- 1. stored above the ground so that ground moisture cannot move back into the wood,
- 2. protected from soil splashing onto the materials, and
- 3. covered tightly with weatherproof tarps to protect the material from precipitation. (coverings that spread out and also cover the ground will act as a greenhouse and allow ground moisture to condense under the cover and will move back into the wood products.) The only exception to covering would be for the delivery of pressure treated lumber which is still wet from the pressure treatment process, which needs to dry out in order minimize shrink stresses when placed in construction.
- When wood picks up moisture it can warp, but more importantly it can become attractive to wood infesting insects. Most wood boring or wood chewing insects will leave materials alone if they have less than 10% moisture content. Wood products must also be protected from mud splashes (from rain hitting the ground adjacent to the wood). All soil contains micro-organisms that initiate and or accelerate decay.
- Materials that are "man-made" such as OSB (Oriented Strand Boardw:Oriented_strand_board), unless treated with copper or borate compounds, are even more suseptible to absorbing moisture and fungal attack. When OSB is exposed to moisture the chipped wood begins to swell, allowing for the edges of the individual 'flakes' to lift, where soil, bacteria, fungal spores, and insects can get leverage.
Foundations and framing
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- The change from chromated copper arsenate pressure treated lumber to alkaline copper quat (ACQ), and copper azole (CA) treatments (substantially increasing the percentage of copper in the wood) is much more corrosive on aluminum and steel elements that are in contact with the wood, and are subjected to moisture. [1]. Recent trends in the use of aluminum for foundation flashing, window flashing, and insect barriers will need to change to materials that are more compatible with this chemistry.
- Aluminum fasteners, steel fasteners [2], and aluminum flashing that are in contact with ACQ, CA treated wood products will, in the presence of water (whether condensate or rainfall) corrode, leaving gaps in the protection intended for structures [3].
- Caution must be exercised even when using galvanized fasteners (Hot dipped Galvanized, or stainless steel are recomended by the pressure treated industry, with a strong preference for stainless steel in critical situations. Corrosion gaps in the flashing or insect sheilds will not likely be visible even in the most thorough building inspections. Termites only need a 1/64th inch opening to access a structure and will build mud tunnels over the treated lumber to get to untreated lumber [4]. Having the potential of four metals in contact with water (Aluminum, copper, steel, zinc) may set up a chemical reaction that will accelerate corrosion.
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