Laying decking on soil: 4 easy steps

Laying decking on soil: 4 easy steps

Wooden decking laid on soil/grass area

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This article walks you though the basics of laying decking on soil. Laying decking on soil can be a fast way to get your decking up without some of the hassle of installing it normally.

Using examples and diagrams, this article will walk through the steps to effectively lay decking on a soil base. 

The steps to lay decking on soil are split the “essential” and “advisable”. The essential steps are needed to make the decking safe and make sure it is usable. The advisable steps will give a better result and potentially a longer lifespan. 

Grey composite decking laid on soil

Materials

Essential

Advisable

Equipment

Essential 

Advisable

Step 1 : Create a solid foundation

Diagram of step 1: digging out are area to lay the decking on soil

Essential

Using the example in our fictional back garden first you need clear out the area where the decking will go. Remove any turf, weeds or debris and create flat surface. You can check this using a spirit level and a string line.

If you are laying decking on uneven ground you may need a different method.

Its important at this stage that you don’t dig any further than you need to. if you are removing turf then going down 50mm should be adequate.

The soil needs to be compact enough to support the weight of the decking without deforming.

Generally speaking, if the soil deforms under the pressure of your foot then it is not compacted enough for the weight of a decking frame. If this is the case the hardcore should be used before laying the decking.

Advisable

Excavate to a level of 200mm below the desired surface level of the decking. Add and compact a 50mm layer of type 1MOT hardcore. This will ensure that there are no soft areas and help to spread the weight of the decking frame more evenly. 

Step 2: Build a decking frame 

Building a decking frame ready to place on the soil base

Essential

Using 100mm x 50mm timber joists create a level and square decking frame. The outer edges should be exactly where you want the decking fascia boards to be. 

The central pieces of wood that you can see will increase the stability of the base and help to keep even spacing between the joists.

Advisable

If you are using timber for the frame it’s a good idea to weather treat it with something strong. The timber is often not as good quality as the decking boards and will deteriorate faster if not treated. 

Step 3: Lay out and level the decking slabs

Diagram of a concrete slab base to support a decking frame

Essential

Lay down a weed proof membrane over the whole area, this will prevent any weeds or grass from growing up through the decking. This doesn’t need to be pegged down as the weigh from the decking will keep it in place.

Using old or cheap concrete slabs, lay out 3 lines on the soil which will act as a solid base for the decking frame. These slabs will spread the weight of the decking and prevent any serious sinking. 

You can use less than the number shown in the diagram but the corners and centre need support and generally speaking the more support the better. 

Advisable

Use some gravel or hardcore to level any uneven slabs. The more even the base is the more even the frame and decking surface can be. 

Step 4: Add and level the decking frame

An example of how the base of decking can be constructed using concrete slabs and a low profile timber frame.

Essential

Place the decking frame on the slabs you laid out earlier. Stand on the frame to make sure there is no wobble. If you find that there is a wobble adjust the slab base until it is gone. 

You will need to adjust the decking until it is evenly supported. Check the surface with a long spirit level to make sure it is both level and flat.

Depending on the length of the joists used the wooded frame can bend which makes it feel stable but will cause issues when attaching the plants to the surface.

Advisable

To make it as sturdy as possible, all cross sections and joints should be supported. A neat trick which avoids having to make lots of adjustments is to use wood off-cuts to create little supports. 

The supports should be screwed into the frame near the cross sections and connect with a concrete slab underneath. 

Now you can lay decking on soil with peace of mind

When it comes to laying decking on soil, the more preparation you are put in the better it will be. If you follow all of the advice (including the advisory points) you should be left with a sturdy and durable decking frame which is ready to have the decking planks installed. 

If you are in the northwest and would like your decking professionally installed then please get in touch

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