THE work of the plumber includes laying sheet lead or zinc1 on roofs and "flats," forming gutters and flashings, lining cisterns, fixing pipes and fittings for water supply and other purposes, also pumps, baths, water-closets, etc.
The surface to be covered with sheet lead is generally boarded. It should be perfectly smooth, even, and the boards thick enough to prevent their warping, otherwise the lead is liable to be damaged by their sharp edges.
If possible, the boards should be laid in the same direction as the fall of the flat or gutter, so that if the boards should warp across their width, the uneven ridges formed will not cause water to lie upon the lead.2
All sheet lead should be laid with a " current" or slope to throw off the water.
The amount of inclination varies according to circumstances; in gutters it must depend greatly upon position, and the space available for the fall. In any case, the current should not be less than 1 inch in 10 feet (1/120), but on flats, where there is no difficulty, it may be made 3 inches in 10 feet.
In order to guard against the effects of contraction and expansion in large pieces under the influence of changes of temperature, nothing larger than a sixth of a sheet - that is, a piece about 10 feet by 3 feet 9 inches - should be used.
Tor the same reason, sheets of lead should on no account be rigidly fixed on both sides, nor should they be soldered to one another.
2 Lead is described as "6 lb. lead," " 5 lb. lead," according to its weight per square foot. 6 lb. to 8 lb. lead are commonly used for Flats, Gutters, etc., 5 lb. lead for Flashings, 6 lb. and 7 lb. for Hips and Ridges, or greater weights if the work is much exposed. (See Parts II. and III.)
The joints necessary between adjacent sheets are made in various ways, so as to allow sufficient play for contraction and expansion.
The joints in the direction of the "current" are made with "rolls," while "drips " are used for those joints which run across the current.
Fig. 456 is the plan of a portion of two roofs arranged so as to show a lead flat, a valley with trough gutter between the roofs,1 a gutter behind a blocking course, also one behind a parapet wall, a valley in the angle formed by two portions of one roof,2 together with hips, chimney and gable flashings, cesspools, drips, etc.
1 Middle, Gutter.
2 Sc. Flanks.
Most of the subsequent figures, 457 to 480, are sections on the lines marked and lettered on Fig. 456, giving details showing how the lead is fixed in the different parts of a roof.
Rolls are joints between two sheets on a flat (rr Fig. 457), formed by fixing under the junction of the sheets a piece of wood about 2 inches diameter, having its upper surface rounded and the lower corners either left square, or chamfered off as shown in Fig. 458. This wooden roll is overlapped by the edges of the adjacent sheets. One of these, u, the " undercloak," is hammered and dressed closely in to cover the roll, reaching as far as the crown, and the edge of the other sheet, 0, the "overcloak" is then beaten and dressed down over the first, as shown.
The laps should be on the least exposed side of the rolls, so that the wind may not blow the lead up, and allow the rain to get under it. Thus in London it is the rule to cloak away from the south-west. The rolls should be about 2 feet apart, sometimes less, but never more than 2 feet 3 inches.
In many cases the inner sheet is dressed right over the roll down to the flat on the other side. This is a waste of lead, and is injurious to the work, for it confines the sheet so much that it cannot expand and contract under changes of temperature.
In many cases a roll such as that in Fig. 459 is used. It is lighter but not so substantial a form as that in Fig. 458.
The outer sheet is frequently continued right over the side of the roll and doubled down, so that about an inch or more lies upon the flat as in Fig. 459. This is intended to make the joint more secure, hut is objectionable, not only because it confines the lead, but also because the water lying upon the flat gets in between the sheets of lead and is drawn up by capillary attraction, so as to pass the joint and soak into the wood rolls and boarding.
Hollow Rolls are in some parts of the country1 preferred to those with the wooden roll or core.
The ends of two adjacent sheets are turned up against one another as at O, Fig. 460, the upper edge of one being bent down over the other; the two are then bent over together to form a roll as at P.
Between the ends of the two sheets so treated is a " clip " or "tingle" 2 (shown in Fig. 460 by a thick line). This is a narrow strip of lead, of which about 2 inches is nailed to the boards.
Similar tingles are fixed at intervals of about 2 feet through-out the length of the rolls, and, being turned over between the ends of the sheets in forming the rolls, secure the latter firmly to the boarding.
The ends of the hollow rolls are dressed over the nosings forming the sides of the flat.
Nosings are rolls formed at the angle between the horizontal surface of the flat and the sloping sides of the roof.
The upper half course of slates is first covered by a flashing, which is dressed about 8 inches upon the slope, turned up, and terminated at the angle of the flat. Upon this is secured a wooden roll, undercut on the lower side, as shown at Z, Fig. 457. Over the roll the lead of the flat is dressed in a manner similar to that above explained.