550 



DETAILS OF CONSTRUCTION. 



exposed to damp, and therefore they not 

 only speedily become decayed, but the 

 ends of the rafters, mullions, or astragals 

 reposing or set in them, are also liable to 

 share the same fate. Stone is well 

 adapted for the purpose when the super- 

 structure is to be metallic, and cast-iron 

 whether it is of that material or of wood. 

 Stone wall-plates are best when they rest 

 on solid masonry or brickwork, and 

 cast-iron, when used in a similar manner, 

 or when the roof is to be supported on 

 columns — in which case they may be used 

 both for upper and lower plates with 

 equal advantage. The first consideration 

 regarding either is, that they be suffi- 

 ciently thick, so as to be strong and 

 capable of sustaining any weight that 

 may be laid upon them, as well as incap- 

 able of becoming twisted or cast, or of 

 being easily displaced ; and this is also 

 necessary in order to admit of the rafters, 

 gutters, astragals, &c, being securely 

 fixed to them. With regard to wooden 

 wall-plates, their form deserves considera- 

 tion, for on this much of their durability 

 and usefulness depends. Their under 

 surface must always present [a plane 

 similar to that of the top of the wall, or 

 the supports they are to rest upon : their 

 sides should be perpendicular to that 

 wall, whether they exceed its thickness 

 or not. The outer half of the top surface 

 should present an angle or slope exactly 

 equal to that of the roof ; the inner half 

 should have a greater bevel, to allow the 

 condensed steam, conducted by the roof 

 to that point, to run freely off. All this, 

 it will be clearly seen, is with a view to 

 keep the wall-plates as dry as possible. 

 They should never, unless in the case of 

 cast-iron ones, have the water-gutters 

 cut out in them : these ought always to 

 be attached. The best gutter is of cast- 

 iron ; and these should be cast, with the 

 edge which comes in contact with the 

 wall-plate, quite straight, so that it may 

 fit closely to it. The lighter the castings 

 are, the better : they should certainly not 

 exceed an eighth of an inch in thickness, 

 and should be so formed that the end of 

 the one may lie within the end of the 

 other, — or in what may be called the half 

 spigot-and-faucet form, set in rust, and 

 secured by a bolt and screw-nut. Lead 

 was long used for this purpose ; but it is 

 apt to get bent, and often to crack from 



expansion and contraction. Zinc has 

 more recently been employed ; but it is 

 neither durable nor sufficiently strong, 

 and scarcely worth the expense of fitting 

 up. Whatever kind of gutters is used, 

 it is of great importance that they be of 

 sufficient size to carry off freely all the 

 water that may fall into them from the 

 roof, and also that they be laid at a 

 sufficient incline, so that the water may 

 flow to the points of discharge, which 

 should not exceed 25 or 30 feet from 

 each other. These dischargers should be 

 cast-iron pipes, laid to carry the water to 

 the nearest tank or cistern ; for rain 

 water is an element too precious in a 

 garden to be wilfully wasted. Where 

 iron wall-plates are to be used, it will be 

 better to have the gutters cast on them, 

 as making both the cheapest, best, and 

 most elegant finish. Both stone and iron 

 wall-plates should be so formed that no 

 water may rest on their upper surfaces : 

 they should therefore be bevelled on 

 both sides, so that it may run freely off. 

 In forming the connections between the 

 rafters, valleys, or astragals, and wall- 

 plates, all mortice joints should be care- 

 fully avoided ; as, however well they may 

 be finished off by the tradesmen, they in 

 time, from one cause or another, become 

 so open as to admit damp, and damp will 

 cause decay. In the case of wooden 

 rafters and wall-plates, the former should 

 be cut with a shoulder to abut against 

 the wall-plate on its inner side, while the 

 point of the rafter should be so fashioned 

 as to rest on the wall-plate, but not be 

 mortised into it. To secure it in this 

 position, a hard wood bolt or dowel should 

 be driven through it, and three parts 

 through the wall-plate. We prefer a 

 wooden to an iron dowel for this purpose, 

 as rust affects the one and not the other. 

 The wood may slightly shrink from the 

 iron in dry weather ; while the iron, not 

 expanding in proportion, opens a way for 

 wet getting in, which, when once in, 

 cannot get out again; whereas the wooden 

 bolt will expand somewhat, perhaps to 

 the whole extent required — as, from being 

 driven in with force, its diameter is a 

 little reduced, and it will have a natural 

 tendency to assume its original size. 

 All wall-plates resting on solid masonry 

 or brickwork should be securely batted 

 or bolted down — a precaution seldom 



