Greenhouse – second hand
There are hundreds of greenhouses offered every day. Sometimes they are good purchases, others are a waste of time. Knowing when to buy and when to walk away is an important skill. But before we look at the nitty gritty, we should examine the alternatives.
A new aluminum frame greenhouse will cost £30 per linear foot for a cheap one to £50 for an expensive one. A wooden frame greenhouse will cost a lot more. The way to work out the value of a second hand greenhouse is to check on the glass.
Glass greenhouse panes cost between £12 and £15 each. PVC ones cost around £8 each. So first of all the number of panes missing on the greenhouse is an important consideration. You should also factor in to the equation how many panes you might break in transport. You never manage to get them all back in one piece, and the merry tinkle in the back of the car as you drive over yet another sleeping policeman is another £15 to add on to the bill. You should estimate that you will break at least two.
So the cost of a second hand greenhouse should be no more than £15 per linear foot, which includes a calculation for replacement panes. Otherwise you might as well get a brand new one.
This calculation aside it means a 6-ft greenhouse should cost no more than £75 to make it potentially a good buy.
But then there are a few other problems to look for before you decide to buy. If you can help it buy a greenhouse that you have to dismantle yourself. There are a number of good reasons for this. You can see exactly that everything is there because the whole thing is already in one piece. You will already know how many bolts you have to buy because you will have a record of the number you have to cut out with a hack saw because they have seized up.
You will also know that all the cross members are in place and if the door works and the window opens. And if all the base plates are actually straight and not a twisted wreck. If the greenhouse is in a ‘flat pack’ pile of cross members and pieces of aluminum, it is more difficult to work out if the whole thing is actually there, and which bits go with which.
Moving and dismantling
Do not attempt to move a greenhouse any real distance, so you have to use a car for example, unless the greenhouse is dismantled into pieces that can be laid flat. The aluminum design greenhouse is really good at withstanding torsion when there is glass in it but even the forces exerted in turning a corner can twist the frame, and if that happens it is useless.
Before you take the greenhouse apart, check it for squareness. This shows itself in two ways. Usually when a pane breaks it smashes altogether and needs replacing. Cracked panes are a ‘tell-tale’ sign of the greenhouse being out of square. You will also see gaps between the glass and the frame.
The next thing to worry about, if you see the frame is not square, is the cross members might be twisted, so have a good check all round. A plumb line will show you the direction of the lean and if you gently push in the opposite direction it should easily go straight.
If you hit the spars with a screwdriver they should have a muffled ring. If they thud or buss there is a problem to be investigated.
When you dismantle, mark the corners and joins with different coloured nail varnish or paint – then you know which bits join without having to make complex diagrams.
Remove all the pains of glass and clean them before putting them between newspaper. Store the glass on an edge and do not put more than five panes together. The glass is held in position by two clips. A spring that locks the glass against the frame and another that allows the top pane to rest on the lower one. Always wear gloves when handling glass.
When the nuts are removed from the frame always screw them back onto the bolt because they corrode in place and are almost impossible to get onto another. If you remember, take a tin of oil with you to pop them in.
The roof and side-walls have rubber seals that act as a cushion between the window and frame. These perish and crack and become useless. Some garden centres do stock rubber seal but, you might find it impossible to find replacements but you can use anti hot spot tape, either cut long-ways (very fiddly) or rolled up (looses stickiness) or in one piece (might be too wide). Whichever way you do this make sure you do not tape up the gulley at the edge of the window frame for the spring clips to go in place and secure the glass.Clean everything – gutters and glass particularly – before you get it to the new position and make sure that all the screw holes and all the drain holes are open.
Before you try to assemble your new (well, old) greenhouse you need to make some preparations. But new spring clips and throw the old ones away – they become corroded and lose their strength. You need four clips for each pane of glass.
You also need to make a base. If you create a concrete base a couple of inches thick, which has anchor points – spaces so you can hammer the anchoring hoops into the soil, you will have the best base there is. You need to make sure the anchoring hoops are well seated, and are uncorroded. You can buy new ones from builders’ merchants and DIY stores.
Assemble the base first and use a piece of square wood to make sure the corners are 90o. Now anchor the base before constructing the rest of the greenhouse. Every joint should be square before tightening up all the nuts.
Make sure the base is securely anchored in position with long anchoring pins
You will need help in getting the walls together – do not let them fall but rope everyone in to hold it up until you have it all bolted together.
A well prepared base will pay dividends over the years
Once the roof is in place you can fix the gutters – if they are separate, and then glaze. Do the lower parts of the roof first, working from the inside if possible (that way you cannot fall onto the glass!)
The top roof-glasses rest on the lower ones with ‘S’ shaped fixings. Then glaze the sides and doors.
The roof light – or window – simply hinges on the frame and locks in position.