Putting decking over an existing concrete slab is a great way to create an outdoor living space without having to pour a new slab. Decking can transform a drab concrete patio into an attractive, functional area perfect for entertaining or just enjoying the outdoors. While it’s definitely possible to install deck boards over concrete, there are some important factors to consider first. In this article, we’ll go over everything you need to know about putting decking over a concrete slab, including how to prepare the slab, choose decking materials, and install the boards properly. We’ll also provide tips for maintaining your new deck surface. By the end, you’ll have all the information you need to decide if adding decking over concrete is the right choice for your home.
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Can You Install Decking Over Concrete?
The short answer is yes, you can install decking over an existing concrete slab. While poured concrete is an ideal base for some types of flooring, like stone or tile, it usually needs to be covered to work with most decking boards. The smooth, hard surface of concrete doesn’t allow deck screws or nails to grip properly. Over time, the decking would become unstable and start to lift or crack.
Installing the deck surface over a framework attached to the concrete allows the decking boards to be securely fastened in place. This provides a solid, even foundation for the decking that will last for many years to come.
Benefits of Adding Decking Over Concrete
– Cost effective – Much less expensive than pouring a new slab.
– Quick project – Can be completed in a weekend.
– Low maintenance – Durable decking materials require little upkeep.
– Customizable – Choose from many deck board colors, styles, and patterns.
– Improved aesthetic – Attractive deck transforms plain concrete.
– Added functionality – Creates a new outdoor living space.
Things to Consider Before Starting
Installing decking over concrete is a big project that requires proper planning and preparation. Here are a few key things to consider before getting started:
– Condition of the concrete slab – Any major cracks, crumbling areas, or uneven spots will need to be repaired or filled first.
– Drainage – Be sure water can drain off the slab and away from the house or standing water will damage decking over time.
– Sun exposure – Full sun can heat bare concrete and cause issues like mold or warped boards. Consider shade elements.
– Access points – Plan how you will enter/exit the new deck area from inside the home or yard.
– Building permits – Most areas require permits, so check with your local building department.
– HOA regulations – If applicable, get HOA approval for your decking project beforehand.
How to Prepare a Concrete Slab for Decking
Proper prep work is crucial for getting a smooth, long-lasting deck surface. Here are the key steps:
1. Clean the Concrete Thoroughly
Start by cleaning the slab to remove dirt, debris, oil, or any other substances that could interfere with adhesion. Use a pressure washer or degreasing chemicals if needed. Rinse well and allow the concrete to dry completely.
2. Repair Any Cracks or Damage
Inspect the slab and make repairs to any cracked, crumbling, or uneven areas:
– Use concrete patch compound to fill small cracks and divots.
– For larger damaged spots, remove loose material and fill with new concrete.
– Level any low spots using concrete leveling compound or mortar mix.
3. Improve Drainage
It’s important that water drains off the concrete slab and away from the structure. Here are some tips:
– Re-grade the soil if needed to promote drainage away from the house.
– Install a French drain along the perimeter if poor drainage is an issue.
– Use a drainage mat under the decking to allow moisture to escape.
4. Remove Protruding Objects
Eliminate any protruding objects like screw heads, nails, or anchor bolts that could puncture the decking material:
– Use a hammer or screw gun to remove any protruding screws or nails. Fill the holes.
– Cut off any metal anchor bolts flush with the concrete using a rotary tool.
– Grind down any small protrusions.
How to Attach Decking to a Concrete Slab
There are a few methods for attaching decking over concrete, each with their own pros and cons.
Option 1: Hidden Fasteners
Many composite and PVC decking manufacturers make special hidden fasteners for attaching their deck boards over concrete:
How they work:
– Plastic clips fit up into grooves on the deck board edges.
– Flanges on the fasteners screw into a wooden framework on the concrete.
Pros:
– Creates a nice, flush surface without visible screws.
– Allows decking to expand/contract with temperature changes.
Cons:
– More expensive than standard screws.
– Not compatible with all deck board styles.
– Harder to remove and replace boards later on.
Option 2: Tapcon Screws
Tapcon concrete screws can be used to attach pressure-treated lumber directly to the slab:
How they work:
– Pre-drill holes for Tapcon screws in the concrete.
– Drive Tapcon screws through the lumber framework into the concrete.
Pros:
– Very secure connection to the concrete.
– Less chance of loosening over time.
– Works with any type of deck board.
Cons:
– Lots of visible screw heads.
– Hard to remove lumber from concrete later.
– Doesn’t account for expansion/contraction of decking.
Option 3: Adhesive with Screws
For a super secure bond, construction adhesive can be used along with Tapcon screws:
How it works:
– Apply adhesive to the concrete slab and bottom of the framework.
– Screw through the lumber into the concrete as normal.
– Adhesive cures to form a waterproof, durable bond.
Pros:
– Extremely rigid, long-lasting connection.
– Helps compensate for any minor slab imperfections.
Cons:
– More time consuming to install.
– Difficult to remove lumber later on.
– Doesn’t allow for expansion of decking.
In most cases, hidden deck fasteners provide the best solution for attaching decking over concrete. Screws or adhesive should be used to attach the framework securely first.
How to Build a Frame for Decking Over Concrete
Once the slab is prepped, you can construct a frame over the concrete to provide a solid base for installing the deck boards.
1. Layout the Framing
– Mark the layout for joists on the slab using chalk lines. Spacing is usually 16″ on center.
– Around the perimeter, mark where ledger boards will be attached. Leave room for decking overhang if desired.
2. Install the Ledger Boards
– Use Tapcon screws and construction adhesive to attach 2x lumber ledger boards around the outer edge.
– Place ledger boards 1/2″ above the slab so decking surface will drain.
3. Cut and Install the Joists
– Cut 2x lumber joists to length according to the layout marks.
– Attach to the ledger board by toe screwing or using joist hangers.
4. Add Blocking Between Joists
– Cut and install short 2x blocks every few feet between joists.
– This helps stabilize the frame and reduces bouncing.
5. Cover Exposed Wood
– Seal any exposed lumber with waterproof paint or coating.
– For better drainage, attach flashing over top of ledger boards.
Once the frame is complete, you can begin installing the decking boards. Be sure to check for level and square as you build the frame.
How to Install Decking Over Concrete
When the framework is ready, it’s time to attach the deck boards. Make sure to follow the manufacturer’s instructions for proper fastening over concrete. Here are some general tips:
1. Plan the Deck Layout
– Choose which direction you want the decking to run and where you want end seams or patterns.
– Stagger boards so end joints fall over different joists.
2. Insert Hidden Deck Fasteners
– Place plastic hidden fasteners into the board grooves, aligned with each joist.
– Screw the fastener flanges into the joists using exterior screws.
3. Position the First Deck Board
– Carefully set the first deck board against the ledger board.
– Pre-drill and use screws on the ends and at ledger board to hold in place.
4. Install the Remaining Boards
– Interlock each subsequent board together with the hidden fasteners.
– Use spacers to maintain even board spacing as you work.
– Trim final board to fit using a circular saw.
5. Complete the Finishing Touches
– Install board edging/trim pieces around perimeter of deck.
– Seal any exposed cut board ends with wood sealer to prevent moisture damage.
– Enjoy your new deck surface!
Be sure to check that all boards are level and securely fastened as you install. Take your time for best results.
How to Maintain Decking Over Concrete
Proper care and maintenance are important for any deck, including decking over concrete. Here are some tips:
Clean regularly – Sweep away dirt and debris. Use composite deck cleaner and a pressure washer occasionally to prevent buildup.
Reseal as needed – Apply fresh waterproof sealant to the deck every 1-2 years. Pay extra attention to end grains and around hardware.
Inspect for damage – Check for any cracked, warped, or rotting boards. Replace damaged decking right away before underlying issues arise.
Control moisture – Improve drainage or add a drainage mat if you notice consistent standing water. Keep dirt and debris swept off.
Watch for trip hazards – Level any boards that become uneven. Refasten any loose decking for safety.
Protect the finish – Place planters, pots, and furniture carefully to avoid scratching decking. Use furniture pads under chair legs.
With proper installation and regular upkeep, decking over concrete can provide many years of outdoor living enjoyment. Just be diligent about cleaning and maintenance. Pay attention to moisture and drainage issues in particular. And refasten or replace any problem boards right away.
Conclusion
Installing decking over an existing concrete slab is an easy DIY project that can add beauty and enjoyment to your backyard. With the right preparation and materials, you can create a surface that looks amazing and will last for decades. Just be sure to:
– Thoroughly clean and repair the concrete first.
– Build a sturdy frame following normal deck construction methods.
– Use hidden deck fasteners or Tapcon screws to attach deck boards securely.
– Maintain the decking by cleaning regularly and resealing every year or two.
– Monitor for issues and make repairs promptly.
With proper installation and care, a deck over concrete can provide an elegant, durable outdoor living area for your home. Just take the time to do it right. Follow the tips in this article and your new deck can be a space you’ll enjoy for many years to come. Let us know if you have any other questions!