Wooden Decking in Harrow

1. Place a post in the corner of the frame you created with the pegs and string. Measure and mark out 100mm from each side.
2. Dig out this soil to a depth of 700mm (watch out for cables or pipes). You should have a 300 x 300mm hole. Repeat for the other 3 corners.
3. Using a brick bolster, split a concrete block in two. Put a section of the block in each hole.
4. Get a length of post longer than you need and place one in each hole. You can cut it down later.
5. Create props on each post to hold them in place until you’re ready to add a cement mix. Check that they’re level. When you’re happy that they are, secure them in place with a concrete mix, making sure you create a slope in the concrete so that rainwater runs away from each post. When the concrete is set, remove the props.
6. Create a string line around each corner post and find the centre point between each. Place a timber batten at each point, ensuring that they’re not spaced any more than 1500mm apart.

1. Working from the corner where the deck will be at its highest above ground level, measure and mark on the post where the highest part of the frame will be.
2. Measure from the far side of one post to the opposite and cut sections of joist to size. Line up a piece of joist with the mark you made and temporarily secure it. Factor in a 2mm fall for every metre of decking so rainwater can run off.
3. Secure the frame to the other corner post, ensuring it’s at the right level. Do this for every side of the outer frame.
4. Using 100mm coach screws with washers hanging on the end, secure each end of the four sections of frame.
5. Mark out where the centre of the support posts will be and secure all of these posts to the frame, except the centre post.
6. Add your central support joists. These should run in the same direction as the deck boards will run. You’ll need to measure from the inside of the frame on one side to the inside of the frame on the opposite side. Attach the joist in the same way as you did for the other posts. Repeat so the centre post is in between two sections of frame and secure the posts with concrete.
7. Trim down all the posts to the correct height using a saw.
8. Add your weed-control fabric and weigh down with gravel across the entire area.

1. Measure 400mm from the centre of the outer frame and mark a line. This will be where the first joist is positioned. Repeat at 400mm intervals down the length of the frame – if the last one will be more than 400mm, add another joist to create enough support.
2. Attach a joist hanger to each end of the joist.
3. Place the joist in position so the centre lines up with the 400mm spacer mark.
4. Secure using external grade screws once you’re happy that the joist is flush with the frame.

If your deck isn’t going to be flat to the ground, it’s a good idea to have some kind of balustrade to avoid any tripping. If the gap between the deck and the ground is less than 600mm, use a 900mm balustrade. If it’s higher than 600mm, the balustrade should be 1100mm tall.

1. Start in one corner of the sub-frame and position the first board across the inner joists. You want the deck board in the opposite direction to the inner joists, ensuring that it’s flush with the frame. Position any end-to-end joins between the deck boards halfway across an inner joist so you can screw both boards into the joist for stability. Make sure you keep a gap of between 5-8mm to allow for expansion of the wood.
2. Begin to screw your deck boards to the joists. You’ll need to secure the deck board to every joist is covers along your deck frame. Use two screws for every joist. Mark where you’re going to add your screws, ensuring that they are at least 15mm from the end of the board and 20mm from the outside edges. Drill pilot holes for the screws, being careful to only drill through the deck board and not the joist. Then screw the decking screws into the holes.
3. Continue to screw in the deck boards, ensuring you leave the correct expansion gap. You can stagger the deck board joins across the deck for more strength.
4. Sand down any cut ends if you need to before applying decking preserver to protect the timber from rotting.