Wooden Decking in Cornwall

Usually, slipperiness is caused by algae or dirt on top of the deck or terrace. A full cleaning treatment should restore the natural grip of the wood or stone. If slipperiness is a persistent problem, consider installing grip mats in high traffic areas of the deck.

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.

• Paving slabs – old or cheap ones are fine
• Timber for the frame and legs
• Type 1 MOT hardcore

1. Mark out the area as we explain in ‘How to lay decking’. Then, dig to 200mm below where you want to surface of the decking to be.
2. Add a 50mm layer of hardcore and make sure it’s compact.
3. Build the decking sub-frame as we describe in ‘How to build a deck frame’.
4. Lay out paving slabs along the edges and in the centre of the area. This will help to spread the weight of the decking.
5. Set the decking frame on the slabs, checking for high or low points and adding off-cuts of timber where needed. Don’t forget to sand and seal these off-cuts with decking preservative.
6. Add your joists and then the deck boards, leaving the recommended gaps of expansion of between 5-8mm.