How to Install Composite Decking over Concrete?
Did you know that one of the most common materials used for outdoor deck spaces is concrete? Many home builders choose to build concrete slabs instead of wood posts because they are convenient and more affordable. Upgrading an outdoor deck from an existing concrete slab to a beautiful patio is also a great choice for DIY enthusiasts. The satisfaction of transforming your deck will outweigh the effort and cost.
Building a deck over a concrete porch may not even require a building permit, reducing the cost and complexity of the project. But before we get into the pros and cons of building a concrete deck, let’s get into how to build a concrete deck. In this blog, we share key things to help you transform concrete into a beautiful outdoor deck space.
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Table of Contents
Can You Put Composite Decking over Concrete?
Yes, it is generally possible to build a composite deck over concrete. This can be done using an existing concrete patio to provide a solution for use. Building a deck over a concrete porch can help homeowners create a beautiful and functional outdoor space. This type of installation is ideal for homeowners who are renovating an outdoor area and don’t want to go through the hassle of removing existing features.
To build a deck over a concrete porch, you first need to make sure that the concrete surface is clean and tidy. You will need to use shims to leave enough clearance before the deck material for proper drainage and ventilation. Then securely fasten the composite boards using the appropriate fasteners, making sure that all the materials are weather-resistant. Composite decking over concrete not only enhances the look of your deck but also extends its life. Read the installation instructions provided by the composite decking manufacturer to see the minimum space required under the deck. Composite decking generally requires three inches or more of free-flowing air space.
Considerations for Building a Deck over Concrete
Inspect the Concrete Thoroughly
Before building a deck over concrete, you need to perform a detailed inspection of the existing concrete slab. The first goal is to assess whether the surface is level. With homeowner use, most concrete slabs have small bumps and depressions that can affect the stability of the composite decking substructure. Use a level to check the entire concrete space, marking any locations that are off by more than 1/8 inch. Minor surface problems can be addressed by using a concrete leveling compound. If the concrete surface is smooth enough, you will also need to watch for cracks or holes, or if the concrete is sinking into the ground.
Build a Substructure
You will need to build a substructure over the existing concrete in order to install a composite deck over it. The substructure is important to provide proper drainage and ventilation, which helps the composite decks not to be under any additional stress.
Installing Composite Deck Boards Using Hidden Fasteners
For decking on concrete, it is crucial to leave proper gaps between boards for the expansion and contraction of the deck and joists. Installing composite decking with hidden fasteners ensures consistent spacing while providing a neat aesthetic.
Want to know the difference between hidden fasteners and traditional screws? Check out Composite Decking Hidden Fasteners vs. Screws.
Should I Repair or Remove Concrete When Building a Deck on Concrete?
If your concrete slab is generally intact, then it’s worth repairing. However, for severely damaged, unstable or completely uneven concrete slabs, we recommend simply removing it.
Concrete Slab Repair
- Pros: Concrete leveling compounds are readily available and require very few tools. Even DIY enthusiasts can easily do the repair work, and the cost of repairing concrete slabs is lower than removing them completely.
- Disadvantages: However, even after repair, concrete slabs may sink and crack, which may affect the stability of the composite decking.
Removal of Concrete Slabs
- Advantages: Eliminates the potential risk of future damage and ensures complete stability of the concrete and composite decking. Decking on concrete will not break down even with use.
- Disadvantages: Completely removing concrete is a physically demanding process, and there are additional costs associated with disposing of concrete debris.
The Best Frame for Building a Deck over a Concrete Slab
Fully Supported Sleepers
This type of framing uses pressure-treated timber that is laid directly on top of the concrete slab and is therefore fully supported by it. This type of framing is cheaper and quick and easy to install. However, timber frames can be affected by moisture, shortening the life of the frame.
Elevated Sleepers
Elevated sleepers are slightly raised to support the sleepers and have better air circulation than the first type of frame, and therefore have a longer lifespan. However, it takes longer to install than a fully supported sleeper.
Traditional Structural Deck Framing
In this method, a traditional deck frame is constructed on a concrete slab. In this type of construction, the deck frame becomes independent of the concrete itself. So you don’t need to repair or remove the existing concrete slab. This type of construction has the best air circulation and framing life.
Is This Project Suitable for Your Family?
Installing composite decking boards on concrete terraces is usually a simple project. However, in some cases, it may take several years for the concrete to complete the settlement.
Beware of the Sunken Terrace
If your concrete is still sinking, it may not be a good idea to install a composite deck on the concrete terrace. When the concrete foundation begins to sink, it may take more than 5 years to stop.
If you decide to build a new platform on the terrace during that time. The new platform will continue to sink with the concrete foundation.
Time and Cost
Installing a composite wood deck on a concrete slab is very simple. However, the time it may take to place the composite decking on the concrete front porch will depend on the size of the area.
A smaller project can be completed at the weekend, but a larger project may take more than five days. In addition to the size of the area, the time required mainly depends on the number of shims required for the sleeper to form a horizontal surface.
The average price for installing a composite deck board on concrete is approximately $30-50 per square foot. And depending on the composite selected, specific site factors, and design.
If you do this yourself, you will halve these figures. Labor and non-decorative materials usually account for two-thirds of the total cost of the project.
List of Tools and Materials Required
Circular saw hammer drill, cordless electric drill, chalk line reel, new floor, self-leveling composite, plastic gasket, flash tape, concrete screw.
Horizontal and Layout
Before laying the frame keel, you need to repair the incomplete flat surface. Pour a thin layer of self-leveling compound on the uneven place to solve this problem.
Once the space is ready, you can start planning the layout. Most importantly, your layout should include the location of the keel frame and how each surface element is related to the other.
Alternatively, you can use the chalk line scroll to create a visual layout of your plan to help guide your installation. EVODEK has 22 years of experience in composite R&D and production. And has a professional engineering service team. If you are worried about the layout of your home, please feel free to contact us for free suggestions!
Place and Install Keel Frame
The keel frame can be placed directly on the concrete. And the Joist can also be horizontal or inclined, as long as its surface forms a plane. Starting from the highest point of the terrace. Put your first keel frame in place and pre-drill the gasket, keel frame, and concrete with a hammer drill.
Fix with concrete screws and penetrate the concrete not less than 1 inch. Place additional keel frames in the same way, using straight edges to ensure that each keel frame is consistent with the last one.
If the waterproof layer has been laid on the concrete surface, screws can not be used. It is recommended to use cement to fix the keel on the concrete surface. Which can not only ensure the overall firmness but also avoid damaging the waterproof layer. Note that the length of screws used at this time should not be too long. In order to avoid penetrating the keel and damaging the waterproof layer.
Installation of the Composite Decking Materials on a Concrete Slab
Placing decorative panels on keel frames is almost the same as building on ordinary decks. It is important to follow the manufacturer’s installation instructions.
EVODEK provides our engineers and homeowner customers with detailed installation services. Not only detailed installation manuals and installation videos. But also one-to-one installation suggestions to ensure that your project installation is smooth. If you do not understand, please feel free to contact EVODEK!
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