SKYLIGHT WORK Where formerly skylights were constructed from wrought iron or wood, to-day in all the large cities they are being made of galvanized sheet iron and copper. Sheet metal skylights, having by their peculiar construction lightness and strength, are superior to iron and wooden lights; superior to iron lights, inasmuch as there is hardly any expan sion or contraction of the metal to cause leaks or breakage of glass; and superior to wooden lights, because they are fire, water and condensa tion• proof, and being less clumsy, admit more light.
The small body of metal used in the construction of the bar and curb and the provisions which can be made to carry off the inside con densation, make sheet metal skylights superior to all others constructed from different material.
Fig. ters to receive the condensation from the inside when the warm air strikes against the cold surface of the glass, while B B show the rabbets or glass-rest for the glass.
In Fig. 146, C C is a re-enforcing strip, which is used to hold the two walls 0 0 together and impart to it great rigidity. When skylight bars are required to bridge long spans, an internal core is made of sheet metal and placed as shown at A in Fig. 147, which adds to its weight-sustaining power. In this figure B B shows the glass laid on a bed of putty with the metal cap C C C, resting snugly against the glass, fastened in position by the rivet or bolt D D. Where a very large span is to be bridged a bar similar to that shown in Fig. 148 is used. A heavy core plate A made
of j-inch thick metal is used, riveted or bolted to the bar at B and B. In construction, all the various bars terminate at the curb shown at A B C in Fig. 149, which is fastened to the wooden frame D E.
The condensation gutters C C in the bar b, carry the water into the internal gutter in the curb at a, thence to the outside through holes provided for this purpose at F F. In Fig. 150 is shown a sectional view of the construction of a double-pitched skylight. A shows the ridge bar with a core in the center and cap attached over the glass. B shows the cross bar or clip which is used in large skylights where it is impossible to get the glass in one length, and where the glass must be protected and leakage prevented by means of the cross bar, the gutter of which conducts the water into the gutter of the main bar, thence outside the curb as before explained.
C is the frame generally made of wood or angle iron and covered by the metal roofer with flash ing as shown at F. D shows the skylight bar with core showing the glass and cap in position. E is the metal curb against which the bars terminate, the condensation being let out through the holes shown.
In constructing pitched skylights having double pitch, or being hipped, the pitch is usually one-third. In other words it is one-third of the span. If a skylight were 12 feet wide and one-third pitch were required, the rise in the center would be one-third of 12, or 4 feet. When a flat skylight is made the pitch is usually built in the wood or iron frame and a flat skylight laid over it. The glass used in the construction of metallic sky lights is usually (-inch cough or ribbed glass; but in some cases heavier glass is used.
If for any reason it is desired to know the weight of the various thickness of glass, the following table will prove valuable.
Weight of Rough Glass Per Square Foot.
Thickness in inches.
*. I. I. . . 1.
Weight in pounds.
2. 2i. 31. 5. 7. 81. 10. 121.