Copper Flashings - A Manual - 1925 - Page 44
As impervious joints are difficult to obtain and expensive to maintain and as neglected leaks result in damage to valuable buildings it is advisable to cover wash surfaces with an impervious and permanent covering. Sheet copper is believed to be the most suitable material for this purpose.
Flashings should be carried entirely over the top of cornices and in most cases should be turned down over the nib far enough to form a drip and allow the water that runs down the wash to fall clear of the moldings. In this way the face of cornices may be kept clean and free from stains of any kind. When the top of a cornice is flashed, it is advisable to carry the flashing entirely through the base of the parapet and connect it with the cap flashing at the back of the wall. In this way water which enters at the top of the parapet is prevented from getting down behind the flashing at the back of the wall and is also prevented from getting underneath the flashing on the top of the cornice. The backs of parapets should be flashed whenever possible and the flashing should be carried over the top of the wall, laying it in the bed joint immediately below the coping. Then, if there is any leakage at the joints in the wash of the coping, the water cannot get behind the flashing, as it often does when the flashing is applied only to the back of the wall.
The unsightly discoloration that is so much in evidence on the underside of balconies indicates the necessity for better protection of these features. It is almost impossible to make the deck of a balcony water-tight by means of a cement or tile finish. A covering of sheet metal should be used in all cases. In flashing the tops of balcony slabs with sheet metal it is necessary to run the flashing out to the nib if the best results are to be obtained. Quite frequently the floor of a balcony is properly flashed, but the flashing terminates in reglets in the base of the balustrade. This practice almost invariably results in the saturation of the balcony slab by water which finds its way in at the joints in the balustrade and runs down behind and underneath the flashing. By carrying the flashing underneath the base course, any water that enters at the joints of the balustrade cannot penetrate to the balcony slab, and the soffit of the balcony is kept dry and unstained.
The washes of pediments and dormers should be completely flashed if staining and other evils of saturation are to be avoided.
While the use of sheet metal for the protection of mortar joints in washes may entail some slight additional expense at the time of the erection of the building, it will be found more economical in the end because the cost of maintenance will be avoided. Moreover, a building that is properly protected at the beginning will retain its original beauty and value.
FLASHINGS FOR TERRA COTTA
In general all built-in flashings should be furnished by the sheet-metal contractor and should be placed by the mason setting the terra cotta. All built-in sheets should be shaped by the sheet-metal man to conform to the measurements furnished by the mason, and sufficient metal left to allow proper connection to the adjoining flashing. In effect these built-in flashings, in the majority of cases, are counter-flashings.
The best method of fastening flashings to the blocks is that shown in Figure 63. Holes for
plugs about ⅜ of an inch in diameter are formed in the terra cotta 8 or 9 inches apart. A small piece of sheet lead is rolled around a large nail, thus forming a hollow cylinder. This cylinder is inserted in the hole and a brass screw a is turned through the copper into it. The lead fills the hole completely and makes a firm anchor for the screw.
Wooden plugs are not suitable, for in driving them into the holes there is danger of splitting the terra cotta and dampness is liable to cause them to swell.
It will be noted from a study the drawings, (Figures 59 to 66), that there is one principle that enters into the erection of terra cotta; that is, to make as complete a cut off as possible so that moisture driving in through open joints, etc., cannot work its way into the interior of the building. This idea should be borne in mind in designing terra cotta construction and in providing proper flashings.
Flashings for terra cotta should be as nearly as possible continuous and should be so placed as to provide a complete waterproofing of the interior.
Balconies, balustrades, rails, copings, etc., require keying to hold them in place. This key or dowel is shown in Figures 59, 61, 62, and 65. It is not easy to get the flashing material over this if it is made exactly to dimension as drawn. As it is quite necessary that the copper be well fitted so that the superimposed pieces shall have a good bearing, it is suggested that the key be made slightly rounded and be shaped with mortar to fit the flashing strip as much as possible.
While it is general practice to make the fastenings of terra cotta of iron and steel, the use of brass and bronze for bars and anchors, and of copper wire is increasing. After the erection of terra cotta these members are concealed, inspection is impossible, joints open up, and dampness enters and rusts iron and steel fastenings. For the best work the hangers of all suspended terra cotta should be of non-ferrous metal, preferably bronze.
While this adds somewhat to the cost of first installation, it insures a permanent job, requiring no
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