Decking on a Concrete Base or Raised on Posts?
This is a query that we are often asked, but it’s not always a simple answer. There are other considerations that have to be taken into account when deciding if a deck should simply be constructed using a joist or bearer frame on a concrete base or if it should be supported using posts that are dug and secured in the ground using concrete such as Postcrete.
When installing a deck, one of the most important decisions is the foundation. Should you build your deck on a concrete base, or should you raise it on posts? Both options have advantages and drawbacks, so making the right choice depends on your specific needs, budget, and site conditions.
Also see our blog on whether a patio or decking is the best choice.Decking on a Concrete Base
A concrete base provides a solid, level foundation for your decking. This method is particularly suitable for patios, low-level decks, or areas where the ground is already firm and even.
When to Use a Concrete Base
If a simple level deck in the garden is required, then digging out an area the size of the required deck, adding hardcore, and pouring a level concrete base would be a straightforward way to go about the project. If a level concrete area already exists or if it’s difficult to dig posts into the ground, then this could be a valid reason to use a concrete or solid base. The decking frame is then easily installed on top, best using slotted decking joists.
Pros:
Stability: Concrete offers a strong and durable surface, preventing movement or sinking over time.
Ease of installation: Laying decking directly on concrete is often quicker and simpler compared to installing posts.
Low maintenance: A well-installed concrete base requires little upkeep and minimises the risk of structural issues.
Ideal for ground-level decks: If you are building a deck at or near ground level, a concrete base eliminates the need for additional structural support.
Cons:
Limited drainage: Water may pool on the surface if drainage is not properly considered, which could lead to moisture damage over time.
Less flexibility: Once laid, concrete is permanent, making future modifications or extensions more difficult.
Potential cost: Pouring a new concrete base can be expensive, especially if extensive groundwork is required
Simple Decking Frame used on a concrete base. Thank you Jacksons Fencing for use of their image used with their Wooden Decking
Raised Decking on Posts
Raised decking is built on posts and is an excellent choice for uneven terrain, multi-level gardens, or when additional height is needed.
When to Use a Raised Deck
A standard raised deck is normally the way most decks are created. A raised deck on posts would typically be used if the ground is not solid, is uneven or sloped, or if it needs to be raised or have elevated sections of decking in different areas.
Pros:
Suitable for uneven ground: If your site is sloped or unstable, posts allow you to create a level deck without extensive excavation.
Better drainage: Elevating the deck improves airflow and reduces the risk of water damage and rot.
Flexibility: It is easier to adjust or extend a deck raised on posts compared to one on a concrete base.
Enhanced aesthetics: Raised decking can create a stylish outdoor space with added features like steps, balustrades, and under-deck storage.
Cons:
More complex installation: Setting posts requires digging, securing footings, and ensuring the structure is level and stable. Some manufacturers design posts like the one in the image below where the joists slot into the top of the posts, making it easier.
Higher maintenance: Wooden posts and beams are susceptible to weathering and may need regular treatment to prevent rot and insect damage.
Increased cost: Materials and labour for post installations can be more expensive than a concrete base, depending on the deck height and size.
Key Considerations for Any Decking Project
Regardless of whether you choose a concrete base or a raised deck on posts, there are a few key considerations to keep in mind:
Weed Suppressant Fabric: This should be used to prevent weeds from growing through the decking in the future. Many decking kits come with weed suppressant fabric included.
Rodent and Animal Prevention: Try to avoid gaps that rodents or other animals could use to get under the deck.
Planning Permission: Always check with your local planning department to ensure your decking project complies with regulations. Additionally, it’s a good idea to discuss your plans with neighbours before proceeding to avoid any disputes.
Which Option Is Best for You?
The choice between a concrete base and raised posts depends on your specific project. If you need a stable, low-maintenance foundation for a ground-level deck, a concrete base is a great option. However, if your site is uneven or you want a more elevated design, posts provide the flexibility and height needed for an attractive, functional deck.
Before making a decision, consider your budget, site conditions, and long-term maintenance needs. Whichever method you choose, ensuring proper installation will give you a durable and visually appealing outdoor space for years to come.
Composite Decking but a Timber Frame/Base?
Composite decking is gaining popularity as more homeowners look for low-maintenance, long-lasting solutions that look the part like Millboard. Its resistance to rot, fading, and insect damage makes it an attractive alternative to traditional timber decking boards. However, when it comes to decking frames, wooden structures remain the most widely used option. High-quality timber decking frames, such as those from Jacksons Fencing, which come with long guarantees, continue to dominate the market. Their strength, reliability, and proven durability make them a trusted choice for supporting decking, even as composite materials become more common for the surface boards.
Updated in April 2025
