Can You Put Decking Over Paving Slabs?

If you are considering installing decking in your garden, you may already have an existing surface of paving slabs and wonder if you can put your decking over the paving slabs in order to save time and money on your project. Paving slabs are common flooring materials in gardens, as they are usually cheap to install and easy to maintain. Despite this, many homeowners want to upgrade and enhance their outdoor space, as concrete paving slabs don’t add significant aesthetic value to your exterior landscape. If you want to change your outdoor flooring from paving slabs to decking, this article is for you.

Laying decking over an existing hard surface, such as paving slabs, is a simple process that can be completed without hiring a professional. We have created a simple step-by-step guide to constructing decking over paving slabs in your garden to ease the project if you are completing it yourself. Often homeowners who are looking to build decking on existing paving slabs have multiple questions about the installation process and extra necessary information such as cost or planning permission. Therefore, we have compiled some frequently asked customer questions to help guide you through the process quickly and smoothly. 

FAQs from Customers

Can you lay decking straight on top of paving?

You can lay composite decking over the top of existing paving slabs. All that is necessary is a substructure frame of joists. In fact, hard surfaces such as concrete paving are ideal surfaces to lay decking onto, as they are stable and durable materials. Laying directly onto existing paving means no requirement for wooden posts, which not only eases the process as there are fewer materials necessary to complete the project but lowers cost too. You will still have to create a substructure using composite joists or battens on top of the paving in order to support the decking to avoid any structural failure. A substructure is necessary to allow airflow and drainage, which will help to stop water from pooling on the decking surface. It is important to note when laying decking on top of paving that the existing paving surface must be in good condition, as damaged slabs can lead to the sinking of the decking on top, affecting its stability and safety. However, if you are constructing timber joists, you will need pedestals or even composite posts in order to raise the decking to prevent rotting or moisture damage. 

How do you cover old paving?

Paving slabs can come in a variety of materials. Paving slabs can be made from concrete, stone or even porcelain. If you want to cover your paving for aesthetic value or to update old paving, you can cover your paving slabs no matter the material, as long as they aren’t damaged to a point that will affect the structural stability of the decking placed on top. You can cover old paving by installing a decking material of your choice over the top of it. You can install wooden decking or composite decking over your paving slabs. 

What are the pros & cons of putting decking on paving slabs?

As with any construction project, there are pros and cons to consider prior to installation. If you are completing the project yourself, this will save labour costs from hiring a professional. However, a con of this is that it will likely take longer to complete the project if you don’t have experience in construction. Additionally, there is more chance of making any mistakes on the project if you don’t have experience with constructing decking, which can lead to material wastage and more money spent on additional materials. A benefit of building directly onto paving slabs is that there is no need to dig up your garden for posts if you are installing or flattening the surface area; this saves time in your project and requires fewer materials and tools, saving you money as well. Despite this, if your paving slabs are cracked or damaged, you will need to replace them in order to have a stable foundation for your decking boards, which will cost you time and money. 

Is it more cost-effective to put decking over paving slabs?

If you have existing paving slabs in your garden and are looking to upgrade the area to decking, it is more cost-effective to build on top of the paving slabs than ripping out the existing material and building on soft ground. The job will be quicker and, therefore, cheaper if you hire a professional to complete the job for you. Additionally, as the concrete paving acts as a solid surface for the frame to be placed on, for composite joists/battens, fewer tools and materials are required to construct the decking, which in turn will bring down the cost of the project. Pedestals will need to be purchased when using a timber frame to support your decking.

Can you lay decking on uneven slabs?

When using composite joists to lay directly on top of slabs to create your frame, you cannot lay joists on uneven slabs, as this would compromise the structural stability of the decking. This is also the case for a timber substructure, however pedestals are a great option for uneven surface.

How do you attach decking to paving slabs?

In order to put your decking on paving slabs, you will need to create a substructure of joists to make a frame for the decking to sit on securely. This is important as every decking project requires a frame in order to allow for airflow and drainage. Without this, the decking will be susceptible to rotting, warping and damage from moisture. This, in turn, will reduce the lifespan of the decking, leading to the need to repair or replace your decking boards, which is costly and time-consuming. 

A subframe provides your decking with the structural stability it needs to be able to safely hold the pressure of people, furniture and anything placed on top of it. Not only would it reduce the lifespan of your decking without one, but it would also be unsafe to utilise. 

Constructing a subframe is a simple process, requiring only joists, joist hangers, screws and a drill. You may need a saw to cut the joists to your desired size. Additionally, you may require pedestals if you are utilising a timber joist frame.

Step-by-step guide

In conclusion, yes, you can put decking over paving slabs. Eliminating the need to dig up any existing surface material. However, you will need to ensure there are no issues or damage to the decking slabs, such as drainage problems affecting the decking on top. It is also important to remember that the material of the frame you are fitting changes the installation process slightly. To construct a timber substructure, you must raise the decking for drainage purposes.

You can easily complete this process yourself by following the step-by-step guide above.