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Quick Answer
Yes, it is possible to build a wood deck over an existing concrete patio. The process involves installing footings around the perimeter of the patio to support the deck frame, allowing for proper drainage under the deck, and using the right methods to anchor the ledger board securely to the house. Proper flashing is critical to prevent moisture issues where the deck attaches to the home. With careful planning and construction, a wood deck can be successfully built over a concrete slab patio.
Building a Deck Over a Concrete Slab Patio
Putting a wood deck over an existing concrete patio is a great way to expand your outdoor living space without having to tear up the slab. However, proper planning and construction techniques are vital for creating a safe, durable deck. Here are some key steps to building a deck over concrete:
Plan the Deck Layout
Carefully measure the concrete patio and determine the size, shape and height of the deck. Account for access points, views and sunlight when laying out the deck. Check on local building codes for requirements like minimum deck footing depths and railing specs. Have the utilities marked to avoid puncturing any pipes or wires during installation.
Install Footings
Since you can’t anchor into the concrete slab, footings are necessary around the patio perimeter to support the weight of the deck. Dig holes for concrete piers or use metal foundation screw piles driven into the ground. Footings may need to extend below the frost line in cold climates. Space footings according to deck load requirements.
Allow for Drainage
It’s important to allow adequate drainage and airflow under the deck to prevent moisture issues. Create drainage gaps between decking boards. Use joist hangers to elevate the joists at least a few inches above the concrete. Grade and fill the soil if necessary to slope away from the house.
Secure the Ledger Board
The ledger board attaches the deck to the house. Use lag bolts anchored into the rim joist or threaded rods epoxied into holes drilled into the foundation wall. Flashing behind the ledger is essential. Check with building codes for proper ledger attachment specifications.
Build the Deck Frame
Construct the deck frame with joists spaced no more than 16 inches on center. Use joist hangers to attach the joists to the ledger board and beams. Check requirements for beam size and connections. Install diagonal bracing. Double up joists under rail posts for strength.
Add Decking
Choose deck boards based on budget, appearance and durability needs. Allow a 1/8″ gap between boards for drainage. Use screws or hidden fasteners for a smooth surface. Stagger end joints between rows. Follow any special pattern layout.
Include Railings
Railings are required on decks over 30 inches high for safety. Choose wood, metal, glass or cable railings to match your deck’s style. Follow code requirements for maximum baluster spacing, handrail gripping size and attachment methods.
Benefits of Building Over Concrete
Adding a deck over an existing slab patio offers many advantages:
– Saves time and money by using the patio foundation already in place
– Avoids damage and mess from jackhammering out the concrete
– Allows you to expand useable outdoor space
– Provides an elevated, more comfortable wood deck surface
– Transitions from indoor to outdoor spaces
– Maintains the functionality of the concrete patio area
Considerations and Challenges
While building over concrete is an option, there are some important factors to keep in mind:
– Requires footings around the perimeter since you can’t anchor into concrete
– Needs careful ledger attachment and flashing methods
– Must allow adequate drainage and ventilation under deck
– Could require railings, compared to low slab patios
– Concrete limits flexibility in shaping the deck design
-May not work with some homes or condo building construction
– Could have complexities working around existing structures
Alternatives to Building Over Concrete
If constructing a deck over your patio slab isn’t feasible, here are a few other options to consider:
Tear Out the Concrete
Completely remove the existing slab to start fresh. This allows full flexibility in shaping a new deck and integrating footings and foundation. However, demolition is labor-intensive, costly and messy.
Build a Floating Deck
Install a deck over the concrete without attaching to the house. This frees the design from the shape of the patio. But it requires more extensive footings and may feel less stable.
Extend from the House
Rather than covering the whole slab, build a deck addition extending from the home to partially cover or abut the patio. This is often the easiest permitting option.
Use Deck Tiles or Pavers
For a simpler upgrade, install interlocking deck tiles or pavers directly over the concrete slab. This avoids construction but has a shorter lifespan than wood.
Stain or Resurface the Concrete
Applying decorative concrete resurfacing, staining or etching can transform the look of the patio without building a deck. This is the lowest cost way to update the space.
Conclusion
Building a wood deck over a concrete patio is often a great way to add outdoor living space without removing the existing slab. With proper planning for footings, drainage, connections and code requirements, you can safely install a beautiful deck over your patio. Consider the costs, construction challenges and alternatives to determine if this project is right for your home and property constraints. Consulting a professional deck builder is advisable for ensuring proper installation and avoiding future issues. With the right approach, you can have the best of both worlds – keeping your concrete patio while gaining expanded deck space.
| Pros of Building Deck Over Concrete | Cons of Building Deck Over Concrete |
|---|---|
|
– Saves time and money – Avoids jackhammering concrete – Expands useable outdoor space – Provides comfortable wood surface – Maintains patio function |
– Requires perimeter footings – Careful ledger attachment needed – Allows less design flexibility – May require railings – Drainage considerations – Some construction challenges |
| Deck Over Concrete Process | Important Construction Tips |
|---|---|
|
1. Plan layout and get permits 2. Install concrete footings 3. Allow for drainage gaps 4. Secure ledger board properly 5. Build deck frame 6. Add deck boards 7. Include code-approved railings |
– Check local building codes – Use joist hangers and braces – Double joists under rail posts – Stagger deck board pattern – Allow 1/8″ gap between boards – Use proper flashing techniques |
Related Questions
How do you attach a ledger board to a concrete foundation?
There are a few methods for securely attaching the ledger board to a concrete foundation wall when building a deck:
– Use lag bolts anchored into epoxied or expansion anchors in the concrete. Check codes for proper bolt sizing and spacing.
– Attach mounting plates to the concrete wall with epoxied anchors, then bolt the ledger to the plates. Provide ample shear strength.
– Drill and epoxy threaded rods into the foundation wall to bolt through the ledger board.
– Use a ledger connection system with proprietary fasteners for concrete applications.
Flashing behind the ledger and sealing is critical. Consult a structural engineer for proper design.
What kind of footings are needed for a deck over concrete?
Decks over concrete patios require footings installed around the slab perimeter since anchoring into the slab isn’t feasible. Here are some footing options:
– Poured concrete piers – These standard footings are economical and very stable.
– Concrete block piers – Stacked blocks filled with gravel or concrete offer adjustability.
– Pre-cast piers – Molded concrete piers simply get lowered into holes and require less digging.
– Metal foundation screw piles – Adjustable galvanized steel pilings twist into the ground and provide quick, minimal-dig installation.
Footing size and depth depends on deck height, weight load and local frost line depth. Consult codes and an engineer for specs.
What is the best way to handle drainage for a deck over concrete?
Allowing water drainage under a deck over concrete is vital. Here are some tips:
– Create drainage gaps between all decking boards using joist spacers.
– Elevate joists several inches above the concrete using joist hangers.
– Set beams on galvanized post anchors with a 1-2 inch gap from the slab.
– Pitch the soil grade away from the home if it currently slopes toward the foundation.
– Use permeable gravel backfill under the deck and at footing holes.
– Incorporate additional joists with subtle crown-up cambers to provide slope.
– Install drainage mat under the decking to manage water flow.
Can you pour concrete footings up against an existing slab patio?
It’s best to keep new concrete footings separate from an existing slab patio when building a deck. Joining the concrete pours allows moisture to transfer and minimizes drainage:
– Set deck footings in the ground at least 1-2 inches away from slab edge.
– Use foam sill sealer as a moisture barrier between footings and slab.
– If necessary, cut a channel between slab and adjacent footings to maintain drainage gaps.
Separate footings allow moisture under the deck and prevent freeze/thaw damage. Check local codes which may prohibit joining concrete pours.