How to Lay Decking on Uneven Ground

Henry A
How to
Nail and Screw decking board

Installing ultra decking is one of the best improvement projects you can undertake. You can install decking almost anywhere, as long as there is a suitable foundation. While they are easiest to install on level grounds, you can also build them on sloped or uneven terrain. With that said, you may need to take a few extra steps to ensure the stability and quality of your composite decking. How do I lay decking on uneven ground?

Lay composite decking

Ways to Lay Decking on Uneven Ground

There are several ways to lay decking on uneven ground. The best approach may depend on many factors, such as the degree of elevation of the ground, the materials you will be using, and the decking type you want to build. Here are some of the methods that you can use.

Using Concrete Support Posts

Support posts are excellent for all types of decks but work best for decking attached to the house. It’s best suited for areas where the direction of the slope is away from the building. Here are the steps on how to build it.

Step 1: First, you will need to clear the installation area. Remove any weeds, grass, and other vegetation in the ground. For the best results, you’ll also want to compact and flatten the installation area with the use of a whacker machine.

Step 2: Next, start digging for the post holes. The hole depth should be at least 30cm (one foot) below solid ground. However, for elevated decks on steeper slopes, you may need to consider other building regulations for the appropriate measure.

Step 3: You have a few options to choose from for the next step. There are several kinds of support post systems. One option is to pour concrete directly into the hole and let it cure according to instructions. After it dries, attach concrete fasteners to the concrete using a concrete drill. Lastly, install the wooden posts into the concrete fasteners. This method is the preferred choice, especially for steeper slopes.

Another option is placing the post inside the hole. For this, you will need to layer the base of the hole with gravel. Then, place the 6×6 or 2×6 wood post into the hole and ensure its level. Lastly, pour the concrete mix to hold the wood post in place. You will also need to create temporary braces on the posts. This option works best for gentler slopes.

Step 4: Since wood posts will have different heights, you will want to run and level a string line across the wood posts to determine where to attach the other subframe parts. Once marked, you can start installing the beams and the joists. Check with your local building standards for the right screws and wood thickness you should use.

Step 5: Once you finish setting the subframe, you can now lay the decking boards. You may also need to install railings for safety and to comply with local building standards.

Using Concrete Slabs

laying decking on uneven ground

Another approach to laying decking on uneven grounds is by using concrete slabs. This solution only works on generally level ground with light sloping. It’s also best for low-level floating decks. Here are the steps you can follow.

Step 1: Mark the installation area and dig at least 20cm deep, removing any grass or weed in the process. Then, whack and compact the whole excavation area.

Step 2: Cover the dig site landscaping fabric next, which helps prevent unwanted weed growth. It also provides water drainage. Then, layer the area with MOT Type 1 sub-base. Alternatively, you can also use a fine and coarse gravel mixture, which is often easier to find. Fill the area at least 50cm deep.

Step 3: Place the concrete slabs in the installation area. Then, place pieces of wood on the slabs to make sure they are level. You can add more gravel or base and readjust the concrete slabs if not.

Step 4: Start building the subframe of the deck, composing beams and joists. Then, place the frame over the concrete slabs. Again, check the subframe if it’s level. Make changes when necessary.

Step 5: You can now lay the decking boards after setting the frame.

Since the decking boards are relatively close to the ground, you may want to choose high-resistant materials. For softwoods, go with Cedar and Redwood. Most hardwoods are excellent for ground-level decks. You can also use non-wood alternatives, such as composite decking materials.


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