1、 STDmAA 35-ENGL 2000 Ob04500 0028002 855 Members of The Aluminum Association Sheet thus, it requires little main- tenance. As an anodized material, it is available in an attractive range of grey, black, bronze, gold and amber colors. Left in its natural state it will weather to a uniform grey. This
2、manual has been prepared to familiarize architects, con- tractors, building officials and students with what constitutes good practice in material selection, design and installation of aluminum sheet metal work for roofing and flashing that is cus- tom fabricated for a specific job. It does not deal
3、 with products or proprietary systems such as siding and roofing and roof-deck systems. Corrosion resistance One of aluminums most useful characteristics is its tendency to develop an extremely thin, tough, invisible oxide coating on its surface immediately on exposure to air. This oxide film, al- t
4、hough only 2 to 4 ten-millionths of an inch thick on first forming, is almost completely impermeable and highly resistant to attack by corroding atmospheres. The thickness of this film increases with exposure time, but the rate of oxide formation gradually decreases as the increasing thickness of th
5、e film adds further protection against corrosion. Where corrosion may be caused by contact with dissimilar metals, measures such as specified in section 3.2 of the specifications included in this book may be taken. In urban and most industrial environments, aluminum does not need painting or anodizi
6、ng, except for decorative pur- poses. in coastal areas, aluminum will long outlast most other metals and coated metals. Workability Aluminum is ductile and malleable and may be bent, formed, seamed or hammered into almost any desired shape. The ease with which aluminum may be handled, transported, b
7、ent, formed or otherwise worked may result in tangible savings. This is par- ticularly so on large buildings and/or where handling and trans- portation are problems. Such savings may be effected not only on the job but in the shops as well. Here, the light weight and good formability of aluminum per
8、mit more work to be turned out per day with less fatigue on the part of the workers. Joining and sealing Mechanical seams and joints for aluminum are the same as for other sheet metals. Aluminum sheet is usually attached to the substrate with aluminum nails or cleats. Rigid joints are achieved throu
9、gh the use of double lock seams or riveting or, in some cases, welding. Soldering aluminum is not recommended, but since the tendency today is to avoid soldering sheet metal work because of the many difficulties involved with soldered joints, this limitation is of little relevance. Synthetic or rubb
10、er based sealants are used where watertightness cannot be achieved with standard seams, such as in the S-lock on top of an aluminum coping cover (see page 27) or in a reglet (see pages 25 and 27). Finishes for aluminum sheet Mill finish aluminum sheet is generally used for roofing and flash- ing app
11、lications and can be obtained plain or in a variety of em- bossed patterns. Embossed sheet has been found to be useful in minimizing oil canning and handling marks. Decorative and protective finishes can also be applied to aluminum sheet. Painted aluminum sheet, plain or embossed, IS available in aw
12、ide range of colors and is finding increased use in residential, com- mercial and monumental construction for valleys, fascias, gravel stops and other flashings. This baked enameled sheet can be cut. pierced, drilled and formed without the finish separating from the base metal. Even ifthe enamel fil
13、m should be broken or the metal exposed at a cut edge or drilled hole, there is no danger of the film flaking or staining, since there is no rust-likecorrosion. Where painted aluminum is marred by metalworking tools in the field, the scratches can be touched up with matching enamel. Mainte- nance of
14、 a painted aluminum roof is less critical than mainte- nance of other painted metal roofs. The paint serves mainly a decorative function, since aluminum is itself corrosion-resistant. Anodizing is one of the most important protective finishes for all types of aluminum. However, since the surface fil
15、m may be crazed by forming and cannot be touched up, as a painted sur- face can, its use is normally limited to preformed shapes that may be anodized subsequent to forming. Anodizing is basically the artificial thickening, by an electrolytic process, of the natural oxide coating that forms on alumin
16、um. The thickened coating is much more resistant to corrosion and all kinds of abrasion than 4 STD-AA 35-ENGL 2000 m ObOLi500 OOL8003 b28 m STD*AA 35-ENGL 2000 ObCl4500 OOLB004 5b4 the thinner natural film. Ordinarily, anodized aluminum sheet is used with a clear finish. However, it can also be obta
17、ined in a range of colors suitable for exterior use in various shades of gold, amber, bronze, grey and black. The colors are achieved by integral color anodizing of certain aluminum alloys or by elecrolyiic deposition of inorganic colorants. Anodic colors achieved with organic dyes are not suitable
18、for exterior use. ALUMINUM SHEET ALLOYS AND TEMPERS Definition of aluminum sheet Aluminum sheet is defined as a rolled product, rectangular in cross section, having a thickness range of 0.006- through 0.249- inch, with the edges sheared, slit or sawed within close limits. It is available as flat she
19、et or in coiled form. If aluminum is thinner than 0.006 inches, it is known as foil, while if it is thicker than 0.249 inches, it is called plate. Using The Aluminum Association Alloy Designation System The alloy and temper generally used for sheet metal work is 3003-H-14. Acceptable alternate alloy
20、s are 1100, Alclad 3003, 3004, Alclad 3004,3105,5005 and 5052, usually in the H14, H24 and H34 tempers. Where sheet is to be anodized, specific al- loys must be employed to produce the desired effects. The composition and tempers of wrought aluminum and wrought aluminum alloys are designated by a st
21、andard system devised by The Aluminum Association and adopted by the American National Standards Institute as ANSI H35.1. The Aluminum Association system divides aluminum and its alloys into eight groups, according to chemical composition: The temper designation consists of a letter-O, H or T. O sta
22、nds for “annealed,“ and indicates the lowest strength and softest state of any particular alloy. H is applied to alloys whose strength can be increased by work-hardening, while T is ap- plied to the alloys that become stronger when heat-treated. A two- or three-digit number is always part of an H de
23、signation. The first digit indicates the type of treatment and the second, the degree of work-hardening attained. H1 identifies alloys that have been work-hardened only; H2 means the metal has been partially annealed after work-hardening, to reduce some- what the degree of hardness. H3 is similar to
24、 H2, but applies to magnesium-containing alloys. The heat-treatment indicated by H3 is called stabilization, as without this treatment, these alloys tend to soften over a period of time at room tempera- tures. The second digit goes from 1 to 9, with 2, 4, 6 and 8 indicating %, %, % and fully hard (O
25、 by itself denotes the fully soft state); 9 is used for extra-hard tempers, and the odd num- bers show intermediate values of tensile strength. The third digit, when added, indicates a slight variation in temper or mechanical properties from the two-digit H temper designation to which it is added. M
26、ore information on aluminum alloys and tempers may be ob- tained from The Aluminum Association publication “Aluminum Standards HH-R-590A, Type II, Class C or, alternately, polyethylene sheet not less than 4 mils thick conforming to Fed- eral Specifications L-P-378B or L-P-512A. Over well vented spac
27、es, the building paper or roofing felt shall be water repellent, but not necessarily vapor proof, and shall conform to Federal Specifications UU-B-790A, Type I, Grade C or D; HH-R-590A, Type II or HH-R-595B, Type I or II. Note: Some building papers and roofing felts conforming to the above Federal S
28、pecifications may contain additives of heavy metals or chemicals corrosive to aluminum and should be avoided. 2.3 Sealants. shall be those conforming to Federal Specification TT-S-230A(l). Use shall be in conformance with manufacturers recommenda- tions. shall be those conforming to Federal Specific
29、ations TT-S- 00227E (1) or ANSI A116.1. Use shall be in conformance with manufacturers recommendations. 2.4 Elastic Cement shall meet requirements of Federal Specifi- cation SS-c-153. 2.5 Fasteners. 2.5.1 CLEATS shall be aluminum of the same alloy, temper and thickness as the sheet being applied unl
30、ess otherwise specified. Cleats shall not be less than 2 inches wide and long enough to 2.3.1 ONE PART SYNTHETIC OR RUBBER-BASE SEALANTS 2.3.2 TWO PART SYNTHETIC OR RUBBER-BASE SEALANTS Table 1 Minimum Nominal Sheet Thickness, Inches (This is not intended to limit thickness of proprietary products)
31、Roofing Residential Non-Resfdent/a/ Standing Seam Batten Seam Shingles Proprietary Systems Flashings Base Cap Ridge, Hip Coping Covers Scuppers Splash Pans Chimney Apron Head Sill Curbs Thru-wall Lintel Spandrel Sill Parapets Gravei Stops 5050 sleeve, 5056 mandrel; 5052 sleeve, 5056 mandrel: 5052 sl
32、eeve, 7178 mandrel and 5056 sleeve, 1020 steel mandrel. Stainless steel or Monel blind rivets are acceptable alternates. 2.6 Paint for backpainting shall be bituminous paint of the cut- back type conforming to specification MIL-C-450 B (1) or TT-C- 494. Where appearance is a factor methacrylate type
33、 lacquers conforming to MIL-L-19537C (2) may be used. 3. PREPARATION OF SURFACES 3.1 General. All surfaces upon which aluminum sheet is to be placed shall be smooth, even and free of small projections and hollows. The surface shall be dry before and during the placing of the aluminum. For wood surfa
34、ces the lumber shall be of good quality, well seasoned, straight and free of knotholes and splits. It shall be laid with all joints true and even and firmly attached with all fastener heads flush with the top surface. On masonry surfaces adequate provision shall be made for receiving fast- eners in
35、accordance with the plans for sheet metal work. 3.2 Dissimilar Metals. Corrosion of aluminum caused by contact with dissimilar metals (galvanic corrosion) shall be prevented by proper design considerations and installation procedures. Notes: 7. Indoors under dry conditions - galvanic corrosion will
36、not occur and, therefore, aluminurn may be used in contact with any metal commonly used in buildings. 2. Outdoors and indoors where moisture is present or conden- sation may occur - galvanic corrosion between aluminum and: (a) Iron and steel is very slow and can be prevented readily by painting the
37、iron or steel with a good quality exterior grade primer and top coat or bituminous paint (Section 2.6). (b) Zinc is insignificant. Zinc even tends to protect the alu- minum. (c) Galvanized steel is insignificant. However, when the zinc is consumed, the steel will rust which may cause staining. In se
38、vere industrial environments this can happen in a relatively short time and the precautions in (a) should be followed. (d) Cadmium plated steel is insignificant. However, when the cadmium is consumed, the steel will rust which may cause stain- ing. As the cadmium coating usually applied is very thin
39、, this may happen in a relatively short time in industrial environments and the precautions in (a) should be followed. (e) Stainless steel is insignificant. (f) Monel is insignificant. (9) Copper, brass and bronze will occur and, therefore, direct contacf of aluminum and these metals should be avoid
40、ed. Drain- age of water off these metals onto aluminum should not be permitted. (h) Lead is insignificant. 3. Highly corrosive environments -such as those on the sea- coast and around chemical plants, mine and mill complexes. re- fineries, etc., may promote galvanic corrosion even though aluminum by
41、 itself has good corrosion resistance. In these en- vironments, advice should be sought from specialists who will be able to recommend appropriate precautionary measures. 3.3 Wood Sheathing or wood surfaces to be covered with alumi- num shall be covered with building paper or roofing felt (Section-
42、2.2). Alternately, -the wood shall be thoroughly painted with two coats of any good qualityexteriortype paint orthealuminurnshall be back painted (Section 2.6). Notes: 7. Kiln dried lumber, impregnated against decay is recom- mended for sheathing, cant strips, coping blocks and fascia boards. Satisf
43、actory preservatives are coal tar creosote. coal tar oil, chlorinated naphthalenes, zinc naphthenate, pentachlor- phenol (with or without addition of zinc derivatives). tributyl tin oxide, orthophenylphenol. Other preservatives may be used but assurance should be obtained from the manufacturer that
44、they are not harmful to aluminum. 2. Aluminum paint, consisting of 2 lbs. of aluminum paste pig- ment (ASTM Specification 0962-66, Type 2, Class 5) per gallon of varnish meeting Federal Specification TT-V-BlF, Type II or equivalent, is an excellent primer and paint for wood. However, any good qualit
45、y exterior type paint may be used. 3.4 Concrete and Masonry surfaces to be covered with alumi- num shall be covered with building paper or roofing felt (Section 2.2) or alternately the aluminum shall be back painted thor- oughly (Section 2.6). Where aluminum is to be caulked into slots or reglets in
46、 masonry, brickwork, or concrete, the slot or reglet shall be filled with sealant (Section 2.3) so that the sealant covers both surfaces of that part of the flashing in the slot or reglet. STD*AA 35-ENGL 2000 ObUY500 0018007 273 Specifications 4. JOINING 4.1 Mechanical Seams and Joints for aluminum
47、shall be the same as those used for other sheet metals. Lap and lock seams shall not be riveted or otherwise fastened together to restrict relative movement unless it is desired to transfer such move- ment to a different location. End joints of formed sheet members such as ridge, hip, valley, gable
48、or rake strips, battens, aprons, gravel stops, coping and cap flashing shall not be riveted or fastened together to restrict thermal movement. Where slope is sufficient to provide drainage and flat widths are less than 8 inches, simple laps may be em- ployed. For flashing with flat widths over 8 inc
49、hes or surfaces with slopes less than 3 in 12, sealant filled controlled slip joints shall be employed. Joints must be installed to allow for the max- imum thermal movement of 118 inch or as determined for the project allowing for the temperature of the metal at the time of installation. Solar radiation can develop material temperatures of 140F on bare aluminum and up to 180F on dark painted metal. Radiation to the night sky can produce surface temperatures 10“ to 15F below ambient air (more in arid regions and at higher altitudes),
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