An existing patio or concrete base can be used as a solid foundation for your deck. Start by measuring and marking out your decking area. If laying the deck over lawn, mark out the area then dig out to a depth of 50mm. Cover the ground with landscaping fabric and add gravel. For soft ground, place paving stones on top of the gravel; this will support the joists and preserve the timber. If you are building a fixed deck that joins onto a house then you will need to attach a wall plate. If you are building a free-standing deck then skip to the ‘Assembling the frame’ section. Start by marking a vertical line that ultimately the end of the wall plate will be placed against. This will mark the corner of the decking. If planning around a step or a sill check the design fits by taking an offcut of deck board, holding it up to the lowest part of the sill and marking a small line beneath it. From that line, drop the board down by 10mm to allow for expansion and draw a level line using a spirit level. This line will be the guideline for attaching the wall plate to the wall so extend this line across the full width of the decking if possible. Then, cut the joist to length. If you need to av...