This section is from the book "Commercial Gardening Vol1", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
The end rafters are cut in the same trough as the sash bars, and care must be taken to cut them in pairs, as they only have a glass rabbet on one top edge for the roof, and one bottom edge for the ends. The best way to avoid mistakes is to set them up in pairs and mark their top ends.
In putting up the roof a start is made by putting up two end rafters, nailing them lightly at the bottom, and leaning the ends together. Holes should be bored previously for all the nails in the bars and joints, to avoid splitting the wood. Two trestles tall enough for the builder to reach the tops of the bars with ease will be required; a strong plank along the tops will enable the builder to put up several bars without shifting. A piece of ridge is now lifted up and pushed between the top ends of the end rafters and held there while an assistant supports the other end of the ridge with a couple of sash bars put in position and lightly nailed in place. The end rafters are now carefully adjusted and nailed fast. A long piece of wood is then put up and nailed to a peg driven into the ground in front of the end of the house; the other end of this piece is nailed to the side of the ridge as soon as the end bars have been got quite square with the plate. When this strut is fixed the roof will remain firm while some more bars are put up, or till the rest of the roof is finished. Two gauges, exactly the width of the glass to be used, are made out of scroll iron or hard wood, and as each bar is put up these gauges are put in where the glass will lie to keep the bars the right distance apart while the nails are being driven. Where the ventilators come a long gauge will be required, as two bars are left out till the ventilator seating is in place. These long gauges want making very carefully or trouble will be met with when the short bars go in. When the end of the first piece of ridge is reached the supporting bars are knocked away and a fresh piece of ridge is put up. The assistant holds up the free end while the builder nails the other to the first piece, and then gets down and supports the free end with two bars as before. The purlin is fixed by boring holes right through the sash bars and the purlin and driving a long wire nail right through and clinching on the inside. While the roof is being built it is as well to nail long boards right across the house, from plate to plate, to prevent any strain being thrown on the plate before the purlin is on and properly tied and supported.
I see that the setting of the plate has been omitted. This is put on a good bed of mortar having a little cement mixed with it, spread evenly along the top of the walls, the plate being well jarred down to settle it in position. As soon as it is on it is fixed to the wall by means of the plate ties set in the wall, coach screws being used to hold it. The drip is then nailed on. In case any of the ties are a little out of the straight it is as well to sight along the wall before fixing, and see if any want letting into the plate or keeping away from it by a small piece of wood. The purlin ties are made out of gas pipe, which can be obtained very cheap secondhand; any blacksmith can work them up to shape. The lengths are all cut right, and then the ends are flattened out, bent over to fit the slope of the purlin, and a hole punched for a coach screw at each end; these are screwed down to the purlin at every 10 ft. The purlin standards may be wood, tied down to a concrete pier at the bottom and screwed to the purlin at the top, or of gas pipe set in a concrete block at the bottom and split, spread apart, and screwed to the purlin at the top. The gas pipe is the better material. If used it is a good thing to slip a 2-in. drain tile on the lower end before it is flattened, to make it grip the concrete. While the concrete is being-put round the end the pipe is held up, and when the hole is full enough it is slipped down till it is bedded on the concrete. Soil is then filled in all round, and cement is made to a thick cream and poured down between the pipe and the standard. This arrangement will keep the standard from rusting where it enters the ground. I have never seen anyone else do this, but offer the idea for adoption by the man who builds to last. I always do it myself; it is very cheap and prevents all rusting through at the ground line. If iron or wooden standards are dispensed with the house must be kept from spreading by iron rods screwed to the plate and set in a concrete block in the border; these are put in every 10 ft. There is very little economy in this method, as unless the walls are very low, almost as much pipe is required as for standards, and these plate ties are always in the way.
If the house is to be heated, a stokehole must be dug at the lowest end of the house. Plenty of room must be allowed for working in front of the boiler and for a division for fuel. The space for fuel need not be very wide if a kind of bin is made of boards fitting into grooves made with pieces of batten fixed to the walls of the hole. Three feet will do nicely for this division. In front of the boiler a space equal to the length of the boiler when set, plus 1 ft. extra, should be allowed for withdrawing the cleaning rods from the flues. The walls of the stokehole are easily made with concrete. The chimney should not be skimped, but should be made 15 ft. high, and with a flue at least 1 ft. square; a larger boiler will want a flue in proportion. A 3-in. drain should be taken from the bottom of the stokehole, so that no water can collect and the pipes can be emptied at any time without trouble. If there is a good natural slope to the ground, and there is some distance to go with the drain, the job may be made less formidable by gradually bringing the drain nearer the surface, and then it can be carried the rest of the way at a depth of 18 in. As long as a fall of 6 in. per 100 ft. is allowed, the drain can be reduced in depth as soon as possible. The stokehole must be made deep enough for the flow pipes to be taken off the boiler easily. In this connection a lot of room may be saved if the boiler is fitted with a short bent flow socket. If more than one house is to be run from the same boiler, screw-down valves must be provided on the flows and returns in each house. All exposed pipes round the boiler and leading to the houses should be coated with asbestos cement, and the pipes from the boiler to the houses are much better boxed right in with brickwork or concrete. A serious amount of heat will be wasted unless this is done. The back rows of pipes can be slung from the plate by iron hooks fixed to the plate with a 2-in.-by-1/2-in. coach screw. If these hooks are made all the same length, and the proper fall has been given to the house walls, the pipes can be set with the greatest ease. For greater security it is best to have the pipe hooks bent over at the top so as to fit the plate, and thus give the coach screw assistance in bearing the weight of the pipes. The front rows of pipes are slung from the purlin standards or placed on brick or concrete piers. These are very simply made with concrete as follows: Holes about one spit deep and 1 ft. square are dug out in a line up the house, where the pipes are to come; pegs are set up in the middle of the holes and the correct rise given to them in the same way as to the pegs used when giving the rise to the walls; 2 or 3 in. of concrete is put over the bottom of the holes and then a little framework of any odd bits of rough wood is put round each peg so as to leave space for the pier to be made 5 in. square. The concrete is now filled in up to the top of the pegs and the piers will be ready as soon as they have set. When the pipes are put on the top they should be bedded in cement mortar. The pipes are put together with cement joints made as follows: The pipes are slipped into each other, then about two strands of pipe yarn are twisted up and driven into the joint with a caulking tool till the end of the joint is reached. Pipe yarn as bought consists of four strands twisted, but this is too thick to be driven in. Three strands are now twisted up and just tucked in all round the joint, leaving a little hole at the top. Make a little cup with the loose ends of yarn and pour into the space between the two rings of yarn cement mixed to a thick cream till no more can be got in. Tuck in the loose ends and drive the yarn in as far as possible. The next day the joint can be faced up with neat cement made into a stiff mortar. Nothing short of a red heat will loosen such a joint, and they will stand all ordinary pressures without leaking; a few drops may ooze through when the pipes are first filled, but this will generally stop in a short time; if not, the facing must be chipped off, and, if possible, some of the yarn scraped out and the joint refilled with cement mortar as before. Hot-water pipes can easily be cut with a sharp cold-chisel to whatever length is required. The chisel should be given a point with a rather wider angle than is usual, and the temper should be as hard as possible to stand without chipping. The wide angle helps in this matter. A mark is made round the pipe where it is to be cut, and the pipe laid on the ground so that it is touching immediately beneath the cut. The line is now followed round with the chisel, giving light sharp taps to the tool with a hammer. As soon as the line is chipped all round, go round again, hitting a little harder, but still as sharply as possible. During the third time round the pipe will probably crack all along the mark and break off clean; if not, the process must be repeated till it does crack. The flow pipes in the house should stand 6 in. higher than the returns, and an air pipe must be fitted at the highest point in each row.