The Complete Guide to Building a Deck on Concrete

Hey there! If you‘re thinking about installing a new deck on top of an existing concrete surface, you‘ve come to the right place. As a professional contractor with over 15 years of experience building and renovating decks, I‘m excited to share everything I‘ve learned about constructing beautiful, durable decks on concrete slabs.

In this comprehensive guide, we‘ll cover all the specifics including:

Preparing the Concrete Surface
Attaching the Deck Securely
Floating Deck vs Traditional Deck
Deck Blocks vs Footings
Choosing Decking Materials
Railings, Stairs and Finishing Touches
Cost Breakdown and Considerations

I‘ll walk through each step of the process in detail so you can decide if a deck build on concrete is right for your home. Let‘s get started!

Why Choose a Concrete Base?

Before we dive in, let‘s look at some of the benefits of using an existing concrete slab as the foundation for your deck:

• Cost savings – Skipping the concrete pour saves big on upfront costs. Materials and labor for the slab can easily cost $5,000 or more.

• Stability – Concrete offers a perfectly flat, rigid surface for attaching the deck. This prevents sagging and helps the finished deck to be nice and level.

• Longevity – Concrete lasts for decades. Pairing it with pressure-treated framing and decking results in an incredibly durable outdoor structure.

• Drainage – Unlike wood, concrete won‘t easily decompose when exposed to standing water or excessive dampness.

• Customization – Turn a drab, aging concrete porch or patio into a gorgeous new living space!

If you already have a suitable concrete foundation on your property, building right on top of it can save tons of time and money compared to pouring a new slab.

Preparing the Concrete Surface

The very first step is preparing the concrete slab by cleaning and treating the surface. This gives the deck framing and hardware the best chance to adhere properly.

Here‘s what I recommend doing in order:

1. Thoroughly clean the slab – Use a stiff broom to sweep off any loose dirt or debris. Then get in there with a pressure washer set to a high PSI and scour away built-up grime, oil spots, algae, mildew and anything else contaminating the concrete. Let the slab dry out completely before moving to the next steps.

2. Check for cracks and damage – Scan the concrete for any cracks, chips, divots or uneven spots. Use a chisel and mallet to open up any tight cracks so they accept filler.

3. Fill cracks and voids – Mix up some concrete repair compound and work it into all cracks and defects using a trowel or putty knife. Smooth it flush with the surrounding concrete. Let cure per package directions.

4. Level uneven surfaces – If you notice the slab tilting in areas or has significant depressions, you can grind down high spots using a concrete grinding tool. Wear a safety mask when grinding to avoid inhaling concrete dust.

5. Etch the surface – Use a mixture of muriatic acid and water to etch the surface. This roughens up the smooth concrete so adhesives and construction materials grab better. Neutralize the acid, then rinse thoroughly.

6. Apply bonding primer – Once the slab is fully prepped, roll on a concrete bonding primer like Loctite Concentrate. This enhances adhesion. Apply it where any ledgers, posts or other items will contact the concrete.

Proper prep work makes a huge difference in the quality and longevity of a deck on concrete. So take the time to do it right!

Attaching the Deck Securely

Now that your concrete slab is prepped, it‘s time to talk about how to securely attach the deck framing and hardware.

There are three excellent options to choose from:

Option 1: Concrete Screws and Anchors

This is one of the easiest and most popular methods. Here are the steps:

• Drill holes into the concrete using a hammer drill and masonry bit. Clean out holes.

• Insert galvanized concrete screws or wedge anchors then tap into place with a hammer.

• Align deck posts, footings, or ledgers over the anchors.

• Use exterior wood screws to firmly screw through framing and into the anchors. This secures everything together.

Attaching deck framing to concrete with anchors and screws. Image from Decks.com

Concrete anchors combined with wood or decking screws offer a super sturdy connection that won‘t loosen or pull out over time like nails might.

Option 2: Concrete Bolts

Another great choice is using concrete bolts:

• Drill properly sized holes into the concrete for the bolts.

• Drop bolts into holes, then hammer them in until flush. Wedge anchors also work here.

• Place deck ledgers and posts over protruding bolt ends.

• Use washers and nuts to finish securing the bolts through the deck framing. Tighten everything down with a wrench or socket.

Concrete bolts attach a deck securely. Image from Home Depot.

For best results, choose 3/8" or 1/2" epoxy coated bolts. This type offers maximum strength and corrosion resistance.

Option 3: Adhesives

If you want a lower profile attachment without screws or bolts poking out, adhesive is the way to go:

• Clean and prime the concrete per preparation steps above.

• Apply a thick concrete bonding adhesive to the slab and the bottom of the deck frame.

• Within the working time, press the decking frame into place while adhesive is still wet.

• Use cinder blocks or other weights to hold framing tightly against slab as adhesive cures. Allow 1-3 days depending on product used.

• Supplementary screws can also be added once cured for extra strength.

As you can see in this photo, adhesives create an ultra low-profile bond since nothing protrudes from the concrete:

Adhesive provides a strong bond without screws, anchors or bolts. Image from Decks.com

I recommend using top-quality outdoor construction adhesive like Loctite PL Premium for this.

In many deck installations, pairing adhesives with mechanical fasteners gives the best results. The combined connection strength cannot be beat!

Floating Deck vs. Traditional Deck

When constructing a deck on an existing slab, you have two primary design options:

Floating Deck

A floating deck rests on top of the concrete, but does not attach directly to it:

• Install concrete footings around the slab perimeter to support vertical posts.

• Attach beams horizontally to the deck posts.

• Lay joists across the beams. Joist hangers keep them elevated.

• Install decking boards over the joists to create your surface.

Floating deck design. Image from Decks.com

Since it does not physically attach to the concrete, a floating deck avoids having to drill or penetrate the slab at all. The key is ensuring adequate drainage so water doesn‘t collect underneath.

Floating decks are quick to construct and great for converting existing patios or walkways into elevated decks.

Traditional Deck

This style actually attaches right to the concrete using fasteners, anchors and adhesives:

• Flatten and prepare the slab as discussed above.

• Drill into the concrete and use anchors, bolts or adhesive to adhere ledgers.

• Attach decking joists directly to the ledger. No elevation needed.

• Install decking surface and other components like railings.

Traditional deck anchored right to the concrete. Image from Decks.com

Traditional decks offer a super sturdy result since the frame connects directly to the rigid concrete foundation. Just take care when drilling into the slab.

Either floating or traditional designs work well. Choose what fits your specific needs and preferences!

Deck Blocks vs. Footings

To provide vertical support for a deck on concrete, you‘ll need an elevated frame. For this, you can use:

Concrete Deck Blocks

• Stackable Pier Blocks made specifically for decks. Set on the slab and stack them up to desired height.

• Built-in channels make them easy to insert and secure posts and beams.

• Super quick and easy installation. Just stack the legos and insert your framing!

• Best for smaller or modular decks. May not offer enough support for large spans.

Poured Concrete Footings

• Footings are dug pits lined with gravel that you fill with concrete. Insert rebar for strength.

• Once cured, footings offer an incredibly sturdy base for attaching deck posts.

• More complex installation but ideal for larger decks. Can support immense weight and span longer distances.

• Often required by code for permanent structures based on deck size and height.

I recommend poured footings for any deck over 120 sq.ft. For smaller decks, the pier block system works perfectly fine.

Check with your city about footing requirements to make sure your plans are compliant with zoning and building codes.

Better safe than sorry down the road!

Choosing Decking Materials

The decking surface boards are a key decision. Here are some top options to consider:

Pressure Treated Lumber

• Classic choice that offers durability and cost efficiency
• Available in pine, fir and other woods. Look for .40 CCA retention or higher.
• Costs $1.50 – $3.50 per square foot installed
• Requires periodic sealing to prevent moisture damage

Cedar

• Gorgeous natural reddish-brown color
• Contains natural preservatives that resist rot and decay
• More expensive than treated pine. Around $7-9 per square foot.
• Weathers to an elegant silver-gray patina over time

Redwood

• Distinctive red tone and straight, dense grain
• Naturally decay resistant like cedar but costs a bit less
• Runs $4 – $7 per installed square foot
• Needs occasional sealing for best durability

Composite Decking

• Made of PVC, wood fibers and plastic polymers
• Won‘t rot, crack or warp like natural wood
• Large color selection, mix and match options
• Around $8 – 12 installed per square foot
• Requires minimal maintenance

Price, appearance and maintenance requirements vary quite a bit between materials. Think about what factors are most important for your project.

I‘m happy to walk you through the pros and cons of any decking option in more detail!

Railings, Stairs and Finishing Touches

Once the decking frame is installed, it‘s time to add those finishing touches:

Railings

Safety railings around the deck perimeter are often required by code for decks over 30 inches off the ground. You have lots of style options:

• Wood railings to match your decking
• Cable and post systems
• Glass panels for contemporary style
• Metal and wire railings in black, bronze or stainless steel

Budget $25-50 per linear foot installed based on materials and complexity. Make sure to follow all local railing height codes.

Stairs

Easy access on and off your deck is a must. Wood stair stringers with composite treads offer a nice balance of durability, traction, and cost.

If space allows, stairs with a landing halfway down are preferable. Price will range from $200 for basic stairs up to $2,000 or more for elaborate multi-flight designs.

Lighting & Other Touches

Finally, don‘t forget those finishing touches like:

• Deck lighting to extend those summer evenings just a bit longer! Go with solar powered LEDs for easy installation.

• Planter boxes, flower pots and other greenery to add some life.

• Benches, drink rails, built-in seating and other furniture to relax in style.

Details like these take your deck from great to phenomenal!

Cost Breakdown

Let‘s look at typical cost ranges for a 200 square foot deck build on an existing concrete slab:

Materials

Decking: $600 – $2,000 depending on type of boards

Framing Lumber: $500 – $800

Hardware (nails, screws, brackets): $250 – $500

Concrete for Footings: $100 – $300

Railing Materials: $500 – $1,500

Estimated Total: $2,000 – $5,000

This doesn‘t include any demolition costs if removing an existing structure. Those can add $500 – $2,000 or more to the project.

Labor

DIY Build: $2,000 – $4,000

Professional Install: $6,000 – $12,000

As you can see, installed costs for a professionally built deck on concrete can range from $8,000 – $15,000. But this gives you a low maintenance outdoor living space you‘ll enjoy for decades to come.

If possible, get multiple quotes before starting your project to find the best value. And don‘t be afraid to tackle it yourself and save on labor. With proper planning and patience, you can absolutely DIY a great looking deck!

Wrapping Up

Creating a wonderful deck on top of a concrete foundation is easier than you might think! Follow the steps and advice above and you‘ll have a gorgeous, functional outdoor living space before you know it.

The most important things to keep in mind are:

• Take time to properly clean and prep the concrete
• Use the right combination of mechanical anchors and adhesives
• Mind local building codes for railings, stairs and footings
• Choose durable, low-maintenance decking materials

Investing in a quality deck will pay dividends for years through expanded living space and increased property value. I hope this guide gives you the confidence to get started!

Let me know if any other questions come up. I‘m always happy to chat decks, give free quotes, and help however I can.

To great outdoor living spaces!