Build Deck Over Concrete: Step-by-Step Guide

Have you ever considered adding a deck to your home to enhance your outdoor living space, but thought that it wouldn't be possible due to your existing concrete slab? Well, let us assure you that you're not out of luck. Building a deck over concrete is not only possible but also a great way to combine two different surfaces into one functional space. Let's delve into the details of this process.

The first step in this endeavor is understanding that you won't be able to simply place your decking boards directly on the concrete. The concrete needs a way to breathe, and the weight of the decking can cause cracking if not properly accounted for. Thus, you need a proper base to construct your deck on top of the concrete. Let's explore how this can be accomplished.

Conclusion of Concrete Before Decking

Before you start construction, it's crucial to ensure that the concrete surface is clean, level, and structurally sound. Any cracks or unseen damage should be repaired to avoid compromising the integrity of your deck.

Once you've ensured the stability of your concrete, you need to create an appropriate base for your deck. This can be achieved in several ways, but two methods are most commonly employed: a pier-and-post system and a float system.

Pier-and-Post System

The pier-and-post system involves installing adjustable piers or post bases onto the concrete. These are typically made of steel or plastic and allow you to set your posts at the correct height for your deck's design.

To install, you'll need to locate where you want your posts, drill into the concrete to create a pilot hole, then set your pier or post base, and secure it with concrete anchors or expansion bolts. Once secured, you can adjust the height as needed.

Float System

The float system, also known as a timber-joist/deck-board system, involves installing timber joists onto the concrete, then securing your decking boards onto these joists.

To create your float base, you'll need to install timber joists evenly across the concrete. To do this, you'll need to secure the joists to the concrete with suitable hardware, such as post-to-patio anchors, which are designed to be used with pressure-treated timber.

Deck Design and Installation

With your base in place, you're ready to start installing your decking. The design of your deck is limited only by your imagination, your budget, and any local building regulations. You might choose a simple, level deck for a large BBQ area, or a more complex design with steps, railings, and balustrades.

Regardless of your design, you'll need to consider the spacing between your joists, typically 400mm or 450mm centers, to accommodate standard decking board widths and ensure stability. You may also want to include a waterproof membrane beneath your decking to protect the concrete from moisture and ensure the longevity of your building.

Installing Deck Boards

With your joists securely in place, you're ready to install your decking boards. This can be done using various methods, including face-fixing, where the boards are screwed directly to the joists, or a secret fixing system, where the boards are supported from below and hidden from view.

Face-fixing is quicker and easier, but secret fixing can give a more finished look, making it a popular choice for higher-end decks. Whatever method you choose, ensure that your boards are aligned perfectly and spaced correctly to allow for expansion and contraction with changes in temperature and humidity.

Adding Railings and Balustrades

Railings and balustrades can greatly enhance the safety and aesthetic appeal of your deck. They come in various styles, from simple metal balustrades to ornate wooden railings, and can be fixed directly to your deck or supported by posts set into the concrete or pier-and-post system.

When installing railings or balustrades, ensure they comply with local building regulations, particularly regarding height and spacing requirements. This will typically involve ensuring that the top rail is at least 900mm above the deck surface.

Congratulations! You now have a beautiful deck that complements your concrete slab and expands your living space. Regular maintenance, including routine cleaning and periodic application of a suitable decking oil or stain, will keep your deck looking great for years to come.

A deck over concrete can be a stunning addition to your home, providing a functional and attractive outdoor living space. So, don't let a concrete slab deter you from your dreams of a beautiful deck. With the right preparation and construction methods, you can transform your home's outdoor space into an oasis of relaxation and entertainment.