CHAPTER III Tue BurtpiInc—lIts PLANNING AND CONSTRUCTION, (Part 3)

be found later. The flashing should be secured by either cast-lead wedges, or strips of copper ? inch wide, folded and hammered into wedges, or by small round pebbles. Iron wall hooks, or oak wedges, are sometimes used but are open to objection; the former on the ground that they rust away and become loose, and the latter on the ground that they shrink. Snow boards or grids should be provided to all such gutters, so that the snow does not impede the flow of water more than neces- sary. These should be kept well up off the gutter. Ventilation of Ends of Roof Timbers. Generally there is no lack of air around roof timbers but it does sometimes happen that there is a closed-in space where air circulation is restricted and where, with the least suspicion of damp in addition, dry rot might find a foothold. Fig. 34 at AB shows an air-brick or grating with a narrow space left between the end of the tie-beam and the brickwork to allow free circulation of air, The outlets from these parapet gutters should be provided with wire guards to prevent their becoming obstructed by leaves or birds’ nests. Gutters and {lashings are often formed of zine, but it is inferior to lead or copper and should be avoided wherever possible. The general arrangement, if copper or zine be used in the two cases just illustrated, is very similar, but the flashings should be THE BUILDING—PLANNING, ETC. 33 “beaded” at the lower edge to stiffen them. An example of a zine flashing is given later under the heading of flat roofs. Flashings and Aprons. Where a wall or chimney cuts through a roof, a small gutter, very similar to that shown in Fig. 31, must be provided, the only difference being that the gutter behind the chimney would be smaller. On the lower side of a feature an “apron” of sheet-lead, copper or zine is provided, secured at its top edge in the same way as flashing and dressed over the slates or tiles as shown in Fig. 32. For a chimney the apron is generally in one piece, but for a long wall it should be of pieces not longer than about 10 feet, well lapped at the joints. At the side abutments, a flashing should be used. In the case of brickwork that of the type known as “stepped”. Fig. 33 shows an elevation of a stepped flashing against the side of a brick chimney stack. It consists of a piece of flashing cut so that its upper edge is in steps, to enable it to be wedged into the hori- zontal joints of the brickwork. The fronts of the steps are cut so that they slope backwards in order to prevent rain driving in between the flashing and the brickwork. If it were so cut that the fronts were vertical and in such a position that they could also be wedged into the vertical joints of the brickwork, the upper edge of the flashing would, it will be seen, be very irregular and un- sightly. The lower end of the flashing is dressed round the corner over the apron, and the joint at the upper end is made, as shown, by dressing over the end of the gutter. The flashing to the gutter is also shown dressed round the corner to form a finish. In the case of copper welting or welding is carried out at the corners. In the case of stonework, the upper edge is generally straight and parallel to the slope of the roof, being turned into a groove or raglet, cut in the stone and, of course, wedged. The lower edge of the flashing is usually dressed over the slates or tiles as shown in Fig. 35, the flashing being shown by a thick line. A superior method of construction is that shown in Fig. 36. In this case the tilting fillet is fixed a little way from the chimney or wall (about 2 inches), and a small secret gutter is formed. Soakers. An alternative method of dealing with such a case is to use what are termed soakers, with a flashing over them. Soakers are relatively small pieces of lead, copper or zine, which may be bent to a right angle and built in with the slating as the roof is covered. An example is shown in Fig. 80. The soakers lap well over one another and either a stepped or raking flashing covers thin top edges. Another use for a soaker is to make a watertight 2—D.S. 34 THE BUILDING—PLANNING, ETC. joint where a pipe or similar feature passes through the slates or tiles. A suitable opening can be cut for the pipe and the lead is dressed upwards against it, and made watertight. The outer edges of the soaker are then dressed over and under the slates exactly as if the soaker itself were a flexible slate. Other Roofing Materials. Corrugated iron sheets are often used for roofing sheds or large temporary buildings. ‘They should be of good quality and well galvanised or they will soon rust through. The sheets are well lapped on all sides and secured by galvanised screws and washers set in white lead. Such a covering should be given a slope of not less than 1in 10. On the decay of any part of the coating, a galvanic action is set up which rapidly destroys the iron covering. It is therefore desirable that this should be painted six months after erection and every few years subsequently. Corrugated asbestos cement sheets have largely superseded galvanised iron; they possess the merits of being non-corrodible and therefore more lasting; they do not need painting; they are less noisy in windy weather. There is a B.S. Code of Practice in this material for those who need special details of the best methods of construction in it. Thatch is a very good covering for country cottages, if the picturesque is required and if the roof has a steep pitch; gutters and down-pipes are not needed, the thatch being given a large overhang at the eaves to throw the rain clear of the walls below. Flat Roofs. Flat roofs may have metallic or bituminous surfaces. The metals in use for this purpose are lead, zinc and copper. Of these zinc is the cheapest, but is definitely much inferior to the other two in durability. Whichever is used, the sheets must not be too large, owing to the expansion and contraction which occur with changes of temperature. For lead flats, a width of from 2 feet 3 inches to 2 feet 9 inches and a length of 7 feet would be about normal size. The fall is in the direction of the length of the sheet and will be about 14 inches in each sheet. The long edges of the sheets should be jointed by means of “rolls”, whilst the cross joints are made by lapping the sheets in vertical “drips”, not less than 2 inches high. Figs. 87 and 88 show the roll formed in lead, the edge of one sheet being dressed half way round a wood roll about 2 inches x 2 inches or nearly to the top. This edge should be rasped away almost to a knife edge and tacked close so that the second sheet (shown in Fig. 88) can be dressed over as an overcloak to lie 14 inches on the flat alongside the roll. The lead must be THE BUILDING PLANNING, ETC, 35 APRON AT LOWER SIDE_. V7 OF CHIMNEY STEPPED FLASHING AT SIDE OF CHIMNEY 33 SECTION THROUGH STEPPED FLASHING AT SIDE OF CHIMNEY SECRET GUTTER AT SIDE OF CHIMNEY COMPLETED ROLL FOR LEAD 15" FIRST SHEET DRESSED WELL SECOND SHEET DRESSED 4» INTO ANGLE, EDGE TAPERED RIGHT OVER ROLL WITH 14 AND NAILED EXTRA ON FLAT AS OVERCLOAK 37 38 36 THE BUILDING—PLANNING, ETC. tafted close in to the angles so that there shall be no fear of lifting by winter gales. é Fig. 39 shows a roll in a zine flat. It will be seen that the shape differs considerably from that of a lead roll, owing to the fact that zine is not soft enough to be readily dressed around a curved surface. The edges of the sheets are turned up against the side of the wood and are held down by clips, or tingles, which are strips about 14 inches wide, placed about 3 feet apart. The roll is then covered by a capping, which is secured to the tingles by clips soldered to its underside. The ends of the rolls are protected by shaped pieces soldered on. Rolls can be formed in copper for roofs that are likely to carry pedestrian traffic as in Fig. 44, or by a triangular roll with only a single seam as in Fig. 51. Other roofs can be made by means of what is called a “standing seam”. This is illustrated in Fig. 40. Double or single lock cross-welts are used for transverse joints, the former (shown in Fig. 44a) for flat and low-pitched roofs and the latter (Fig. 44b) on steep or vertical surfaces. Figs. 41 and 42 show lead “drips”. The lower sheet is let into a rebate or sinking on the edge of the upper boards at A, so_as not to cause a ridge there, and the upper sheet laps over it, and extends along the lower flat, as shown in Fig. 41, or the member marked X may be retracted a little as in Fig. 42 with the lower sheet of lead dressed back so as to form an anti-capillary groove. Fig. 43 shows a zine drip. Instead of being turned into a rebate or sinking, as with lead, the top edge of the lower sheet is bent forward and the upper sheet is bent to form a roll or bend around it. Where a metallic flat abuts against a wall the sheet is carried up the wall for a minimum of 6 inches and covered by a flashing, exactly similar to the flashing used at the side of a gutter; such a flashing is shown in Figs. 81 and 84, A flashing suitable for a zine flat is shown in Fig. 45, the lower edge being beaded to check its tendency to curl outwards. This tendency is usually guarded against on copper flashings by means of a bead and a 2-inch wide copper cleat every 18 inches. Bituminous Flats. Flat roofs are now more frequently con- structed of concrete in combination with steel and, although these can be covered with copper, asphalt and built-up bituminous felt are the most likely to be used. These materials are sanitary, damp-resisting, tough, durable, non-absorbent and slightly elastic, so that slight movement of the substructure does not crack them. Being to all intents and pur- THE BUILDING—PLANNING, ETC. 37 poses jointless no rolls or drips are needed. The chief objection to them is that, owing to their black colour, heat and cold’ are easily transmitted through them to the room below and painting with white or light-coloured paint does not seem to remedy this fault appreciably. It can, however, to a great extent be remedied by covering the surface-with thin slabs of precast concrete or _ asbestos, bedded and jointed in sand and bitumen; this is especi- ally desirable on roofs of asphalt, as this substance is liable to perish if exposed to the ultra-violet rays of direct sunshine. Natural asphalt is laid in two layers on one or two layers of bituminous felt. The thickness of the asphalt should be } inch to 2 inch. Where an asphalt flat abuts against a parapet (or other) wall, the asphalt should be carried up the wall for at least 6 inches, the top edge being secured by being let into a 1 inch x 1 inch chase cut in the wall and covered by a metal flashing as in Fig. 45 or the asphalt may be carried right through the wall to form a damp- proof course to prevent rain soaking into the exposed part of the parapet and from seeping downwards. The right-angled junction between the horizontal and vertical faces should be protected by a 2-inch fillet of asphalt laid as a separate operation. The surfaces concerned should be warmed and cleaned by the temporary appli- cation of hot mastic before the fillet is formed. Fig. 46 shows a similar feature in bituminous felt on a timber sub-structure, suitable for the flat roof of smaller buildings or portions of buildings. Eaves Gutters for Flat Roofs. Where asphalt flats are to dis- charge into an caves gutter, a strip of lead or copper may be bedded between the two layers of asphalt and dressed down into the gutter as shown in Fig. 47. The verge or edge, if there is no parapet wall, may be raised as in Fig. 48. The outlets from box gutters in asphalt flats are formed in various ways, but need special care, more so than with eaves gutters and cast iron fitments with gratings, and recesses to take the edge of the asphalt are perhaps the best as in Fig. 49. Bituminous felt, which is felt soaked in hot bitumen, is a fairly satisfactory alternative to asphalt and is usually rather cheaper. Generally three layers of felt are used, each being laid in a brush coat of hot bitumen. Some hot bitumen is poured over the last layer, brushed even and either sanded or covered with fine gravel or tarmacadam; alternatively, it may be covered with concrete or asbestos slabs, which protect it from the action of sunlight and reduce the thermal conductivity of the roof. 38 THE BUILDING—PLANNING, ETC. —— Neg DE LEAD DRIP SS WITH ANTI- CAPILLARY METAL FLASH/NG : 3 LAYERS ZINC OR COPPER J FLASHING OF FELT 3" ASPHALT IN 2 Wy me TRIANGULAR COATS ON FELT Yy UNDERLAY 2" TRIANGULAR FILLET FORMED AFTER CoaTs ARE LAIO 45 THE BUILDING—PLANNING, ETC. 39 Students intending to specialise in flat-roofed buildings to any extent should certainly study the British Codes of Practice in asphalt and other forms of flat roofing. Defective Pipes and Fittings. These are an occasional cause of dampness, but one which is always avoidable. Well-designed and properly fixed fittings, together with pipes fixed against internal walls, need never be a cause of dampness. Where pipes are fixed against external walls, the danger of damage from frost is much greater, but there are many methods of protection in the way of easing them with non-conducting materials, such as hair felt, slag wool, and similar things. Let us next consider the construction and equipment of the building from other standpoints of a sanitary or hygienic nature. Partition Walls. If walls are plastered, the plaster should be carried down behind the skirting board to prevent the entrance of vermin. The old-fashioned lath and plaster partition with its timber posts or studs should not be used. It takes up more room than a partition of fire-resisting slabs and affords a refuge for ver- min. ‘There are many types of solid slab partition, made up of _ thin, strong slabs, readily finished with plaster on either face. They have, however, the drawback that they are apt readily to transmit sound. Hollow tile partitions are now much in use. They are terra-cotta or brick, with two or more cavities, across which are thin connecting webs. They are lighter, more fireproof and more soundproof than solid partitions of equal thickness. Their faces are either smooth or keyed to take plaster facings. Wall Finishes. There should be as few surfaces as possible on which dust can collect. Elaborate mouldings, cornices, high-relief lincrusta or anaglypta should be avoided on this ground. In hospitals, where absolutely sanitary conditions are a sine qua non, internal angles are avoided entirely, all angles, including those between walls and floors, being rounded. Walls should be plastered in order to give a smooth surface on which but little dust can collect. The wall surface can be finished with paint, distemper or paper. The first named is generally out of the question on account of condensation, but effectually pre- vents the absorption of impurities by the plaster. Washable distemper, having a dull surface, is pleasing in appearance and can be readily cleansed. Washable distemper is a thoroughly sanitary material, but common distemper is much inferior. If the surface is good and entirely free from damp penetration, plastic emulsion paint gives a pleasing and satisfactory surface. It may 40 THE BUILDING—PLANNING, ETC. not be so good in a kitchen or bathroom where condensation is to be expected. : Paper, unless it is of the variety known as “sanitary” wallpaper, has a rough surface which readily collects and retains dust. The appearance of sanitary wallpaper, with its slight glaze, prevents its extensive use. Whenever wallpaper is renewed, the old paper should be entirely removed from the walls, as it will have absorbed dirt and possibly not be free from germs, while behind it will be decomposed paste in most cases. The walls should be well washed down with water containing a disinfectant before repapering. For such rooms as sculleries, bathrooms, and water-closets, a glazed surface is desirable for the walls. For sculleries, tiles or glazed bricks are the best, failing which the walls should be painted or varnished. For bathrooms, enamelled walls are good if tiling is objected to. A lining of enamelled zinc, forming imitation tiling, is quite sanitary. If expense prevents either of these alternatives, varnished paper may be used, but ordinary unvarnished paper is quite unsuitable. Non-absorbent wall surfaces have the drawback that they encourage the condensation of moisture, but their sanitary advantages outweigh this consideration. W.C. Walls. For closets, it is a good plan to tile the walls, or, at any rate, to put a tiled dado, with enamelled walls. Here, again, if it is a matter of strict economy, paint, or varnished paper, may be allowed as a