Here the sashbars are similar to those in the roof, the only difference being in the large size, which, as they help to support the roof, are 3 in. by 3. They are mortised into the wall-plate n, which is about 6 in. by 2 1/2 in. or 3, as may prove most suitable, and into an eave-plate o 4 in. by 2 1/4. The angle pieces p for the corners of the building are 4 1/4 in. by 3, and have rebates for glazing and for ventilators to shut into. When side ventilators are introduced, they consist simply of a frame 2 1/4 in. by 1 1/2, grooved for the glass, with sashbars mortised into the frame, and are suspended by hinges to a fixed bar, 2 1/2 in. by 1 1/2, into the upper side of which the top side fixed sashbars are mortised. Although mention is made of side ventilators, it is by no means intended to imply that they are an indispensable necessity, for if the roof ventilation be put through, side ventilation is not wanted, and fixed sides point of course to a considerable saving. Let, therefore, the roof ventilators run from end to end of the roof and consist of a clear space of quite 2 ft. in width, so as to admit so large a volume of air as to ensure a brisk and thorough circulation. Avoid a cheap opening apparatus; let it be strong and yet so easy that a touch may set it in motion.

The best principle is that of a spiral shaft and stout-jointed levers by which the ventilators may be regulated to a nicety. The brickwork of the sides and ends consists of 5 courses above ground and 6 courses below, inclusive of the footings. The walls are 9 in. thick, and the footings are respectively 13 1/2, 18, and 22 1/2 in., so that 1 yd. in length of wall and footings will require 112 bricks; and to make enough mortar for 500 bricks it requires 3 bush, new grey lime and 18 bush. sand.

The doors should be 1 1/2 in. in thickness, and the doorsteps 4 in. by 3, with rebates and beading as shown by t; one for door, the other for glass. The central stage has upright supports 2 in. by 2, and the braces are 3 in. by 2. The strips u forming the shelves are 2 in. by 1, with 1/2 in. spaces between every 2 strips. The woodwork of the side stages v is of the same size.

The glass for the roof is 21-oz. seconds; size of squares, 20 in. by 12; for the sides and ends l6-oz. answers very well. The hot-water pipes are 4-in., and slightly elevated above the floor on pipe stands as shown.

Instead of the pillars h, with spreading arms, many will prefer to use simple uprights and tie the main rafters together across the house by iron rods, merely stepping them into the eaves board instead of mortising. The wall, too, may with advantage be made of concrete, where the materials are handy.

Figs. 619 to 621 represent a combined greenhouse and potting shed, designed to be portable. It is span-roofed, situated so as to be exposed on all but the north side, and erected on a bed of earth or masonry 10 or 12 in. above the surrounding ground and 6 or 8 in. wider than the base of the structure. To provide against the building being disturbed by high winds, 4 posts about 2 1/2 ft. long, and 5 in. square, are driven into the ground near the corners, and the ground-plate of the greenhouse is secured to them by 5/8-in. coach screws. The size of the combined greenhouse and potting shed (the latter being at the north end) is 18 ft. long by 8 ft. wide outside. The ground-plate a, running all round the base, is 1 1/2 in. deep, 5 in. wide, and is formed into a frame 8 ft. 1 in. wide and 18 ft. 1 in. long. Fastened at the corners are 4 upright posts b, 4 in. sq. and kept in a vertical position by 8 struts c, which greatly help to stiffen the framework, until the boards are fastened over it. The space between the end posts is divided on either side of the house into 5 equal spaces by 4 posts, 3 of them d being 4 in. by 3 in. and the fourth e 4 in. by 4 in. This latter divides the potting shed from the greenhouse.

These are all 4 ft. 9 in. long, and as they are mortised into the wall-plate f at the top, and the ground-plate a at the bottom, each of which is 1 1/2 in. thick, the space between the wall-plate and ground-plate is 4 ft. 6 in. The wall-plate f is 4 in. wide; 6 other posts g, 7 ft. 4 in. long, 3 in. thick, and 4 in. wide, are mortised at one end to the ground-plate a, and at the other are nailed to the rafters h. Of these, 2 at either end form the door-posts, of which the doorways i are 6 ft. 3 in. high by 2 ft. 3 in. wide. The rafters h k are nailed at one end on the wall-plate f, and on the other to the ridge-board I, which is 18 ft. 3 in. long, 6 in. deep, and 1 in. thick. Those lettered h are 2 in. by 3 in. and those lettered k of the form shown in section; they are all 4 ft. 9 in. long.

The Sides 618

These rafters can be purchased of the section shown, and should be all carefully placed at equal distances, when the width must be measured, and the glass ordered accordingly. To ventilate the house, about 9 in. next to the ridge-board on one side should be unglazed, and the space covered with 1/2-in. board, hinged in 4 lengths to the ridge-board, and arranged so as to be easily opened from the inside, as shown at m, and the same must be adopted at the bottom of the opposite rafters, where 4 lengths of board n are hinged to the wall-plate /. The outward thrust of the rafters can be counteracted by pieces of wood used as ties, as shown at o. The house should be glazed with glass 16 oz. in weight to the sq. ft. With regard to doors, the amateur had better get them made by a carpenter, as, to look well, they require good work, and they are not expensive. The framing of the sides must be covered with 1/2- or 5/8-in. boarding, tarred or painted on the outside, and the spaces between the inner and outer boards filled with sawdust, which is a slow conductor of heat.

The best material for construction will be thoroughly dry, soft deal, as free from knots as possible; and it will save much trouble to obtain the different pieces of the sections shown, only a little larger, from saw-mills, so that he will only have to plane them, and follow the drawings in cutting to required length. When all the woodwork has been put together, and is thoroughly dry, the knots are stopped, and the whole framing is given one coat of white-lead; this will make the putty in the glazing hold well. Then the glass is put on of the required width, the length of each piece being 15 to 18 in., and each overlapping the next to it by about 1 1/4 in. This completed, the inside and outside wood should receive 2 good coats of pale stone colour or white paint. The heating apparatus employed consists of a small circular boiler p, tank r, and piping s, the fumes of the fuel being carried away by the capped stovepipe t. The pipes s for conveying the hot water, should be 2 in. or 2 1/2 in. in diameter, and lie immediately under the stage u.

The Sides 619The Sides 620

When a suitable wall is available, it is often preferred to make a lean-to greenhouse, in which case the roof is considerably modified. If the greenhouse is to be 6 ft. high in front and about 8 ft. wide, the roof must slope upwards at the back to a height of about 10 ft. If the back wall does not admit of this, the front wall must be made lower, or the floor must be sunk: the latter alternative is very undesirable as conducing to dampness. The construction of the roof and the upper part of the framing is shown in Fig. 622. The bar a is mortised at one end into the tall upright h, which is secured to the wall by strong hooks; at the other end it is mortised into the front top plate c, and throughout its length it is supported on the ends of the uprights of the lower part of the frame d, all of which are mortised into the bottom plate. From the bar a rise a number of uprights e supporting the outside rafter f. The intermediate rafters are partially supported by a tie bar g running from end to end. They all abut at the upper end against the wall-plate h, to which they are securely nailed, and at the lower end they fit on to the top wall-plate c as shown.

The 2 outside rafters are 4 in. by 2 in. in section, but the smaller ones are only 4 in. by 1 1/2 in.

The Sides 621