Construction Cost Guide for a 12 x 12 Deck, With Breakdown


Decks are one of the more budget-friendly ways to add a room to your house. A deck will cost much less than adding a similar size room to your home. For example, the cost of a 12 x12 deck.

A 12 x12 deck can range in cost from $2 200 to $13 000, but the average will be $6 000. Costing $40 a square foot but can be as little as $15 or as high as $85, depending on the deck’s features. A pressure treated deck is the most economical, with composite being the more expansive option.

Regardless of building a 12 x 12 deck or not, the size is good for breaking out construction costs. Almost anything you can build on a 12 x 12 deck can be included on a larger deck. Getting you a sense of price even if you are planning something more extensive.

As I am sure, you noticed there is a big range in cost for a 12 x12 deck. These costs vary with footing selections to the railing and, of course, the decking. Planning how your deck will look, function and be built will determine its price.

First, let’s give a quick breakdown of the levels of 12 x 12 deck designs. Examining features at each price range.

A 12 x 12, 5/4 Treated Platform Floating Deck Costing $2 200

For a little over $2 000, you get a 144 square foot platform in the back yard.

Getting your feet off the dirt, with a level floor to set up a table with a few chairs.

Six deck Blocks cost $300, supporting the two double 2×8 beams.

Non-ground contact 2×8 treated substructure cost $1150. The non-incised lumber will support the platform without breaking the bank. It easily lasting seven to fifteen years depending on moisture level and how close to the ground the wood is.

5/4 x 5 ½ decking running perpendicular to the joists cost $700, with exposed end overhanging the deck’s edge. This decking pattern keeps the cost down both in labour and material.

Building the deck yourself will reduce costs even more. Labour for a 12 x 12 platform floating deck is around $1 000. With your sweat, the prices go down to about $1 200. Cost could be further reduced by looking for deals on lumber and watching for sales.

At this price, the deck does not have railings, steps or skirting. It is essentially a platform close to the ground to set up a few chairs and enjoy being in your yard. An excellent start to get you outside but with no added features to improve the deck’s appearance or make it more usable.

Average Cost for a 12 x12 Floating Deck with Aluminum Railing, $6 000.

Transforming the yard platform into an outdoor room. Adding railing and steps while dressing up the deck increases its appeal and use. Now it’s now just a floor but a room in your backyard. Set up furniture and enjoy the extra space.

An additional room to enjoy the great outdoors.

2 Tread Step Down to the Yard, costing $450, adding steps to the deck to ease getting on and off the deck to the yard. Not cheap, but does significantly increasing the usability of the deck. Making stepping of the deck more comfortable and saving you from having to climb back up.

5/4 Tread Decking with Picture Frame Border, Cost $1 100. Improving the appearance of the decking with a picture frame border. By adding a deck board along the ends of the deck boards. The extra boards creating a nice clean look on all sides of the deck. The addition of picture framing will require extra decking, blocking, and labour costing $400.

Clean Skirting Around Deck, Cost $300. Another nice element improving the look of the deck and keeping pests from under the deck is skirting. A simple design to keep the cost down while closing in the area under of the deck, is vinyl privacy lattice. The small holes will keep skunks out while limiting the view under the deck. The lattice is economical, requiring minimal support and is easy to install.

Under Deck Weed Control, Cost $50. Improving the appearance under the deck by stopping vegetation growth under the deck. Weeds make both the underside of your deck and yard ugly. A cheap solution is placing landscape fabricOpens in a new tab. under the deck. Minimizing weed growth while costing as little as $20 for a roll, but you will be better off paying a little more for more robust fabric.  With no gravel to hold down the material, strength is important.

Aluminum Railing with Pickets, Cost $2250. A ground-level deck does not require a guard rail, but railing will improve the deck’s appearance and use. Something about railing makes you use the deck more fully, with the fear of falling off the edge removed. Aluminum railing requires little maintenance and is easy to install. The railing is only for three sides of the deck and down the steps assuming the deck will be beside the house. Costly, yes, but often worth it with greater use of the deck.

With all these features, a 12 x12 deck will cost around $6 000.  A reasonable price for an additional 144 square feet of living space.

If your taste and budget are a little bigger, more can be added to a deck.

Cost for 12 x12 Freestanding Composite Deck, $13 000

You can always spend more, but for $13 000, you get a deck with class, privacy, usability with minimal maintenance.

An Outdoor oasis for enjoying the comforts of home and outdoors with minimal maintenance.

The amount of maintenance is the most significant difference between a 5/4 wood deck and a composite deck. Which is also affects the price the most. Material requiring less maintenance will cost more initially but will cost less over time. Exchanging labour costs for material cost. Composite costs five times more than treated deckingOpens in a new tab. but will require almost no maintenance. Where treated decking needs to be stained or seal multiple times over its lifetime. Pay now, or pay later. Either way you will pay for it. 

So, what does thirteen thousand buy you?

Concrete Footings Dug to Below the Frost Level cost $1 000. Supporting the deck from below the frost level will increase the deck’s strength and reduce seasonal movement. The added stability of frost footings also allows the deck to be attached to the house’s foundation. Making a permanent connection between the house and the deck. Along with a consistent step from the door to the deck.

Gravel Ground Cover Under the Deck cost $425. With the addition of gravel, the appearance of the area under the deck is improved. Also, the stone increases drainage, reducing rotting of the deck’s substructure. The rock also holds the weed fabric in place, minimizing the chances of movement and weed growth.

Deck Substructure Treated for Ground-Contact cost $1 600. All exterior wood should be treated for fungi and rot, increasing the life of your deck. Using incised wood for the deck substructure increases the level of treatment. The potential of joist rotting is reduced even further.

On top of additional treatment, installing joist flashing under the decking protects the joist’s most venerable part from rot. Protecting your investment longer, increasing the life and appearance of the deck.

Vinyl Lattice Skirting with Composite Battens cost $1 000. Wrapping the underside of the deck with low maintenance vinyl lattice, accentuated with composite fascia boards. Keeping the material and maintenance consistent with the decking. It not only keeps critters and garbage out from under the deck but also gives it a classy look.

Matching Low Maintenance Composite Fascia Boards cost $650. Composite fascia board is a must with composite decking finished with skirting. The composite material reducing maintenance of the rim joist and ties the two together. I wouldn’t even think of installing composite decking without a fascia board.

25+ years low Maintenance Composite Decking cost $3625. There is a lot a choice in low maintenance decking both in cost and appearance. Many imitating wood spectacle with excellent tractionOpens in a new tab. and feel. But the best thing is maintenance, or how little maintenance is required.

Most quality composites come with a 25-year warranty, but you can upgrade to PVC decking, extending their life to over 50-years. Whichever you choose, the biggest advantage is going to be less work. But the appearance compared to treated decking is to be enjoyed.

To add even more class is to wrap the deck with a picture frame border to cover the ugly decking ends. You can ascent the border with a contrasting colour to make the deck pop all the more for a little extra.

Composite Steps to the yard cost $950. What use is a room in your backyard if you can’t get to it. Composite steps continue the low maintenance down to the yard while making it easy to enjoy both your yard and deck. They should be enjoyed together.

Glass Railing with 6′ high Privacy Wall cost $2900. Railing helps to increase safety and enjoyment of the deck. The glass panels don’t obstruct the view while keeping maintenance to a minimum.

Replacing the railing on one side with 6′ (1.8m) high obstructed glass railing, shelters the deck from the wind while increasing intimacy on the deck. The comfort level felt on the deck increased with the addition of a privacy wall.

All these features create a deck that can be enjoyed for years. All while keeping work maintaining it to a minimum.

Possible Additional Costs When Building a 12 x12 Deck

With all construction, there is always the possibility for a few additional costs. Items that are particular to your yard or things not generally included but would be valuable for you. 

Staining of Wood Decking costs $150-450. All wood decking will last longer and look better if stained. There are many different stains available with different colour and durability. The longer they last, the better. Wood is not low maintenance but no need to do more work than you have to.

Recently new stains have been released promising three years or more on decking surfaces. These are definitely something to look for. Way better than stainOpens in a new tab. every year. The trade-off is often these are opaquer stains, hiding the beauty of the wood. But with pressure-treated decking, this is not a problem as it is not naturally a distinct wood pattern.

Another option is to keep the brown from the factory colour and only seal the wood. The most significant advantage is less prep work while still preserving the wood. Repelling water is the primary value of deck stain or sealer. Treated wood is already protected against fungi and rot but needs protection against moisture. Which sealer does without the complication of staining colour and blending. Brush it on, dry and enjoy our deck. Less fuss.

The biggest cost of staining is labour. Which makes it often a job better performed by yourself. Stain for a 12 x12 deck will cost $80 or less. The rest is labour costs. If you do the work yourself, you will save a few hundred dollars and get to spend a few hours on your deck.

Waste and Dirt Removal cost $150-350. Keeping your yard clean during and after construction is worth more than first realized. I have had clients comment that they appreciate the deck but more that their yard is kept clean while the deck is being built and is left clean for them to enjoy their deck. Without having to clean up first, this can only be done with trips to the landfill to dispose of waste, with the dumping fees quickly adding up.

With dirt, it really depends on what level your yard is developed and how many holes you need to dig. One more saving of a floating deck as there is less dirt to deal with.

You can save some money if you can spread out the dirt under the deck before framing. Grading away from the house while disposing of the extra dirt.

You will not want to spread this out on the yard unless you have not sodded the yard yet. As most of the dirt from the holes will be clay and will not be suitable for grass growth.

Better to budget for dirt removal and not need to worry about the dirt after. If planned for from the beginning, it is a lot smaller chore and will cost less.

Demolition of the existing deck costs $750-1000. If you are replacing your existing deck, you will need to budget for removal. Out with the old, in with the new. But this will cost you. Depending on the deck’s size, it could be a couple of days of labour plus a few trips to the landfill.

Overhead shade costs $250-$10 000. Your deck helps you enjoy the sun outside, but the sun’s glare will often become overwhelming. A little shade makes all the difference in deck enjoyment.

Deck shades vary greatly in cost. A simple shade sail attached to four post will cost the least but is much more temporary in nature. A built-in cedar pergola will greatly enhance the deck’s feel and look but could easily cost more than the deck itself.

The best deck shades for a smaller deck are often a retractable umbrella with a base or awning from the house. Even some deck tents or pergola kits are designed for decks that are more durable in design than a wind sail but are not as costly as a built-in structure. Mid-range in cost are a great option for providing shade without requiring set up every time you wish to use your deck.

Angled Decking costs $200-$400. A nice touch with the field deck boards is changing the direction of the boards. A very common design element is running the decking at forty-five degrees to the house and joist, changing the deck’s feel. This look is best done with a picture frame border finish off the decking ends, so include that in the budget.

All one-inch decking boards need additional support when run at an angle. Additional joists and blocking will need to be added to support the decking run at an angle. Plus, the angle cutting of the decking increase waste.  

For 5/4 decking, this increase cost around $200 for a 12 x 12 deck. For the same deck in composite, being a more expensive decking will increase the deck’s cost by $400 or more depending on decking costs.

Raising the Elevation of the Deck costs $400. Most decks are less than three feet (0.9m) from the ground. Requiring small post and bracing and can be built from the ground. But raising the deck higher from the ground increases cost with additional material needed and labour. Working off ladders or scaffolding will slow down construction, increasing the time and cost to build the deck.

Permits cost $275. This can vary a lot by the scoop of the permit and jurisdiction it is required. A simple deck and plan may cost less, but if detailed drawings are needed along with development permits or bylaws relaxations can easily triple the cost of a deck permit.

Conclusion of 12 x 12 Deck Costs  

A small deck can be an excellent addition to your home. A place to sun, grill outdoor, and just enjoy being at home more but knowing the cost before committing to building a deck is a must.

Every yard and house are different, which can impact the cost of a deck. What type of deck you select will significantly impact the budget. A simple treated wood ground-level platform, not requiring permits, frost footing or being attached to your house, will cost around $2 000.

For a more defined space with railing and a more rigid construction attached to your house, you should budget around $6-8 000. With 5/4 wood decking requiring some maintenance but with low maintenance aluminum railing, A large enough budget to get the deck you want without deleting deck essentials.

If your deck’s annual sanding and staining doesn’t appeal to you or you just love the look of composite decking. And in my opinion, many composite and PVC deck boards bring a look to the deck worth the extra money just for appearance. The low maintenance is a bonus.  For a composite deckOpens in a new tab., you should budget $13 000, which will allow for a few more features. Of course, you can always spend more, but that will be enough to start the conversation about adding an outdoor room to your home without adding a bunch more work.

Whichever deck works for you and your budget. Remember, decks are for pleasure, so get out there and enjoy.

Ryan Nickel

A Red Seal carpenter, passionate about building decks to be enjoyed.

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