Cleaning the glass and plastic glazing
For cleaning the greenhouse glass on the outside you can use only water. A hose and a long-handled brush will do the job. If the greenhouse is very dirty then you should brush the glass with a solution of kettle descaler. Protect your skin and eyes by wearing gloves and goggles. Rinse off the solution thoroughly with running water. You can also use a window cleaning solution but this will not remove the ingrained dirt. If dirt is trapped between overlapping panes, use a thin plastic label to loosen dirt and algae then remove the dirt using a water jet from a hose. Shading washes are best removed by rubbing them off with a cloth.
Panes of glass and plastic panes that are slightly cracked may be temporarily repaired with transparent glazing tape, but broken and badly cracked panes should be replaced as soon as possible to prevent harm to plants. For replacing a pane in an aluminium alloy greenhouse you have to remove the spring gazing clips and adjoining pane if necessary and reglaze using the old clips. If the panes are bedded on linseed putty, remove the glazing tacks and the panes of glass carefully. Chip away the putty with a chisel to leave a smooth surface. Clean the glazing bars with abrasive paper before reglazing. Apply a priming paint to any unpainted or untreated wood on the glazing bars. When the paint is dry, replace the panes by setting them on a bed of putty or glazing mastic using glazing tacks to hold them.
Gutters and downpipes
Check that gutters and downpipes are in good repair. Use a hosepipe to clear any blockages. If you found any small leaks on your gutters you can seal them with mastic or other sealant. If the gutters are badly leaking you must replace the leaking section completely.
Aluminium greenhouses require only minimal structural attention. They lose their bright color in time, but the greyish patina that forms protects the metal from the weather. Steel frames and fittings should be checked for rust and treated with rust remover if necessary. Repaint them every few years to keep them in good shape.
Cut out any rotting wood and replace it. Apply woodworm killer and renew any rusty hinges. Softwood greenhouses need regular painting in order to keep them in good shape. Strip off flaking paint, wash down then apply primer and good quality exterior wood paint. Hardwood greenhouses are more rot-resistant. They only require a coat of wood preservative every year or two.
Windows and ventilator fans should be checked for ease of operation, working parts oild if necessary and glass or plastic cleaned.